Confounding by indication in non-experimental evaluation of vaccine effectiveness: the example of prevention of influenza complications

Learning healthcare systems in cardiology: A qualitative interview study on ethical dilemmas of a learning healthcare system

Background

Implementation of an LHS in cardiology departments presents itself with ethical challenges, including ethical review and informed consent. In this qualitative study, we investigated stakeholders' attitudes toward ethical issues regarding the implementation of an LHS in the cardiology department.

Methods

We conducted a qualitative study using 35 semi-structured interviews and 5 focus group interviews with 34 individuals. We interviewed cardiologists, research nurses, cardiovascular patients, ethicists, health lawyers, epidemiologists/statisticians and insurance spokespersons.

Results

Respondents identified different ethical obstacles for the implementation of an LHS within the cardiology department. These obstacles were mainly on ethical oversight in LHSs; in particular, informed con sent and data ownership were discussed. In addition, respondents reported on the role of patients in LHS. Respondents described the LHS as a possibility for patients to engage in both research and care. While the LHS can promote patient engagement, patients might also be reduced to their data and are therefore at risk, according to respondents.

Conclusions

Views on the ethical dilemmas of a LHSs within cardiology are diverse. Similar to the literary debate on oversight, there are different views on how ethical oversight should be regulated. This study adds to the literary debate on oversight by highlighting that patients wish to be informed about the learning activities within the LHS they participate in, and that they wish to actively contribute by sharing their data and identifying learning goals, provided that informed consent is obtained.

Current Approaches to Vaccine Safety Using Observational Data: A Rationale for the EUMAEUS (Evaluating Use of Methods for Adverse Events Under Surveillance-for Vaccines) Study Design

Post-marketing vaccine safety surveillance aims to detect adverse events following immunization in a population. Whether certain methods of surveillance are more precise and unbiased in generating safety signals is unclear. Here, we synthesized information from existing literature to provide an overview of the strengths, weaknesses, and clinical applications of epidemiologic and analytical methods used in vaccine monitoring, focusing on cohort, case-control and self-controlled designs. These designs are proposed to be evaluated in the EUMAEUS (Evaluating Use of Methods for Adverse Event Under Surveillance-for vaccines) study because of their widespread use and potential utility. Over the past decades, there have been an increasing number of epidemiological study designs used for vaccine safety surveillance. While traditional cohort and case-control study designs remain widely used, newer, novel designs such as the self-controlled case series and self-controlled risk intervals have been developed. Each study design comes with its strengths and limitations, and the most appropriate study design will depend on availability of resources, access to records, number and distribution of cases, and availability of population coverage data. Several assumptions have to be made while using the various study designs, and while the goal is to mitigate any biases, violations of these assumptions are often still present to varying degrees. In our review, we discussed some of the potential biases (i.e., selection bias, misclassification bias and confounding bias), and ways to mitigate them. While the types of epidemiological study designs are well established, a comprehensive comparison of the analytical aspects (including method evaluation and performance metrics) of these study designs are relatively less well studied. We summarized the literature, reporting on two simulation studies, which compared the detection time, empirical power, error rate and risk estimate bias across the above-mentioned study designs. While these simulation studies provided insights on the analytic performance of each of the study designs, its applicability to real-world data remains unclear. To bridge that gap, we provided the rationale of the EUMAEUS study, with a brief description of the study design; and how the use of real-world multi-database networks can provide insights into better methods evaluation and vaccine safety surveillance.

Reduced COVID-19 hospitalizations among New York City residents following age-based SARS-CoV-2 vaccine eligibility: Evidence from a regression discontinuity design

BACKGROUND

In clinical trials, several SARS-CoV-2 vaccines were shown to reduce risk of severe COVID-19 illness. Local, population-level, real-world evidence of vaccine effectiveness is accumulating. We assessed vaccine effectiveness for community-dwelling New York City (NYC) residents using a quasi-experimental, regression discontinuity design, leveraging a period (January 12-March 9, 2021) when ≥ 65-year-olds were vaccine-eligible but younger persons, excluding essential workers, were not.

METHODS

We constructed segmented, negative binomial regression models of age-specific COVID-19 hospitalization rates among 45-84-year-old NYC residents during a post-vaccination program implementation period (February 21-April 17, 2021), with a discontinuity at age 65 years. The relationship between age and hospitalization rates in an unvaccinated population was incorporated using a pre-implementation period (December 20, 2020-February 13, 2021). We calculated the rate ratio (RR) and 95% confidence interval (CI) for the interaction between implementation period (pre or post) and age-based eligibility (45-64 or 65-84 years). Analyses were stratified by race/ethnicity and borough of residence. Similar analyses were conducted for COVID-19 deaths.

RESULTS

Hospitalization rates among 65-84-year-olds decreased from pre- to post-implementation periods (RR 0.85, 95% CI: 0.74-0.97), controlling for trends among 45-64-year-olds. Accordingly, an estimated 721 (95% CI: 126-1,241) hospitalizations were averted. Residents just above the eligibility threshold (65-66-year-olds) had lower hospitalization rates than those below (63-64-year-olds). Racial/ethnic groups and boroughs with higher vaccine coverage generally experienced greater reductions in RR point estimates. Uncertainty was greater for the decrease in COVID-19 death rates (RR 0.85, 95% CI: 0.66-1.10).

CONCLUSION

The vaccination program in NYC reduced COVID-19 hospitalizations among the initially age-eligible ≥ 65-year-old population by approximately 15% in the first eight weeks. The real-world evidence of vaccine effectiveness makes it more imperative to improve vaccine access and uptake to reduce inequities in COVID-19 outcomes.

PICK-ing Malaysia's Epidemic Apart: Effectiveness of a Diverse COVID-19 Vaccine Portfolio

Malaysia rolled out a diverse portfolio of predominantly three COVID-19 vaccines (AZD1222, BNT162b2, and CoronaVac) beginning 24 February 2021. We evaluated vaccine effectiveness with two methods, covering 1 April to 15 September 2021: (1) the screening method for COVID-19 (SARS-CoV-2) infection and symptomatic COVID-19; and (2) a retrospective cohort of confirmed COVID-19 cases for COVID-19 related ICU admission and death using logistic regression. The screening method estimated partial vaccination to be 48.8% effective (95% CI: 46.8, 50.7) against COVID-19 infection and 33.5% effective (95% CI: 31.6, 35.5) against symptomatic COVID-19. Full vaccination is estimated at 87.8% effective (95% CI: 85.8, 89.7) against COVID-19 infection and 85.4% effective (95% CI: 83.4, 87.3) against symptomatic COVID-19. Among the cohort of confirmed COVID-19 cases, partial vaccination with any of the three vaccines is estimated at 31.3% effective (95% CI: 28.5, 34.1) in preventing ICU admission, and 45.1% effective (95% CI: 42.6, 47.5) in preventing death. Full vaccination with any of the three vaccines is estimated at 79.1% effective (95% CI: 77.7, 80.4) in preventing ICU admission and 86.7% effective (95% CI: 85.7, 87.6) in preventing deaths. Our findings suggest that full vaccination with any of the three predominant vaccines (AZD1222, BNT162b2, and CoronaVac) in Malaysia has been highly effective in preventing COVID-19 infection, symptomatic COVID-19, COVID-19-related ICU admission, and death.

Assessment of Effectiveness of 1 Dose of BNT162b2 Vaccine for SARS-CoV-2 Infection 13 to 24 Days After Immunization

IMPORTANCE

The BNT162b2 vaccine showed high efficacy against COVID-19 in a phase III randomized clinical trial. A vaccine effectiveness evaluation in a real-world setting is needed.

OBJECTIVE

To assess the short-term effectiveness of the first dose of the BNT162b2-vaccine against SARS-CoV-2 infection 13 to 24 days after immunization in a real-world setting.

DESIGN, SETTING, AND PARTICIPANTS

This comparative effectiveness study used data from a 2.6 million-member state-mandated health care system in Israel. Participants included all individuals aged 16 years and older who received 1 dose of the BNT162b2 vaccine between December 19, 2020, and January 15, 2021. Data were analyzed in March 2021.

EXPOSURE

Receipt of 1 dose of the BNT162b2 vaccine.

MAIN OUTCOMES AND MEASURES

Information was collected regarding medical history and positive SARS-CoV-2 polymerase chain reaction test and COVID-19 symptoms from 1 day after first vaccine to January 17, 2021. Daily and cumulative infection rates in days 13 to 24 were compared with days 1 to 12 after the first dose using Kaplan-Meier survival analysis and generalized linear models.

RESULTS

Data for 503 875 individuals (mean [SD] age, 59.7 [14.7] years; 263 228 [52.4%] women) were analyzed, of whom 351 897 had follow-up data for days 13 to 24. The cumulative incidence of SARS-CoV-2 infection was 2484 individuals (0.57%) during days 1 through 12 and 614 individuals (0.27%) in days 13 through 24. The weighted mean (SE) daily incidence of SARS-CoV-2 infection in days 1 through 12 was 43.41 (12.07) infections per 100 000 population and 21.08 (6.16) infections per 100 000 population in days 13 through 24, a relative risk reduction (RRR) of 51.4% (95% CI, 16.3%-71.8%). The decrease in incidence was evident from day 18 after the first dose. Similar RRRs were calculated in individuals aged 60 years or older (44.5%; 95% CI, 4.1%-67.9%), those younger than 60 years (50.2%; 95% CI, 14.1%-71.2%), women (50.0%; 95% CI, 13.5%-71.0%), and men (52.1%; 95% CI, 17.3%-72.2%). Findings were similar in subpopulations (eg, ultraorthodox Jewish: RRR, 53.5% [95% CI, 19.2%-73.2%]) and patients with various comorbidities (eg, cardiovascular diseases: RRR, 47.2% [95% CI, 7.8%-69.8%]). Vaccine effectiveness against symptomatic COVID-19 was 54.4% (95% CI, 21.4%-73.6%).

CONCLUSIONS AND RELEVANCE

In this comparative effectiveness study of a single dose of the BNT162b2 vaccine, results were comparable to that of the phase III randomized clinical trial.

Effectiveness of a hand hygiene program to reduce acute gastroenteritis at child care centers: A cluster randomized trial

We aimed to assess the effectiveness of an educational and hand hygiene program in daycare centers (DCCs) and homes on acute gastroenteritis (AGE) incidence in children attending DCCs.

METHODS

A randomized, controlled, and open study of 911 children aged 0-3 years attending 24 DCCs in Almería (Spain) with an 8-month follow-up was employed. Two intervention groups of DCCs families performed educational and hand hygiene measures, 1 with soap and water (soap and water group; n = 274), another with hand sanitizer (hand sanitizer group [HSG]; n = 339), and the control group (CG; n = 298) followed usual handwashing procedures. We compared AGE episode rates with Poisson regression model.

RESULTS

seven hundred fourteen AGE episodes were registered, significant differences between HSG and CG children were found during December and January. A multivariate model was applied and the adjusted incidence rate ratios by rotavirus vaccination found significant differences when children were previously vaccinated, the children in the soap and water group had a higher risk of AGE episodes (incidence rate ratio: 1.28, 95% confidence interval:1.0-1.64), compared with those in the HSG.

CONCLUSIONS

This study demonstrated that hand hygiene programs that included hand sanitizer were most effective in the winter months. Further, the largest reduction of AGE episodes occurred in the children that followed hand hygiene programs including hand sanitizer and educational measures for DCC staff, parents, and children, and were vaccinated for rotavirus.

The effect of neoadjuvant short-course radiotherapy and delayed surgery versus chemoradiation on postoperative outcomes in locally advanced rectal cancer patients - A propensity score matched nationwide audit-based study

OBJECTIVE

To investigate differences in postoperative outcomes between short-course radiotherapy and delayed surgery (SCRT-delay) and chemoradiation (CRT) in patients with locally advanced rectal cancer (LARC).

BACKGROUND

Previous trials suggest that SCRT-delay could serve as an adequate neoadjuvant treatment for LARC. Therefore, in frail LARC patients SCRT-delay is recommended as an alternative to CRT. However, data on postoperative outcomes after SCRT-delay in comparison to CRT is scarce.

METHODS

This was an observational study with data from the Dutch ColoRectal Audit (DCRA). LARC patients who underwent surgery (2014-2017) after an interval of ≥6 weeks were included. Missing values were replaced by multiple imputation. Propensity score matching (PSM), using age, Charlson Comorbidity Index, cT-stage and surgical procedure, was applied to create comparable groups. Differences in postoperative outcomes were analyzed using Chi-square test for categorical variables, independent sample t-test for continuous variables and Mann-Whitney U test for non-parametric data.

RESULTS

2926 patients were included. In total, 288 patients received SCRT-delay and 2638 patients underwent CRT. Patients in the SCRT-delay group were older and had more comorbidities. Also, ICU-admissions and permanent colostomies were more common, as well as pulmonic, cardiologic, infectious and neurologic complications. After PSM, both groups comprised 246 patients with equivalent age, comorbidities and tumor stage. There were no differences in postoperative complications.

CONCLUSION

Postoperative complications were not increased in LARC patients undergoing SCRT-delay as neoadjuvant treatment. Regarding treatment-related complications, SCRT-delay is a safe alternative neoadjuvant treatment option for frail LARC patients.

Determinants of vaccination uptake, and influenza vaccine effectiveness in preventing deaths and hospital admissions in the elderly population; Treviso, Italy, 2014/2015-2016/2017 seasons

Seasonal influenza is an important cause of morbidity and mortality, particularly among the elderly population. Determinants of vaccination uptake and its impact on health outcomes in the seasons 2014/2015–2016/2017 in elderly living in Treviso area (Veneto Region, North-Eastern Italy) were evaluated. A retrospective cohort study was conducted combining information from several health administrative databases, and multiple Poisson regression models were applied to evaluate the influenza vaccine effectiveness, also adjusting for confounding factors. MF59-adjuvanted trivalent-inactivated vaccine was mainly administered. Data from more than 83,000 elderly people were analyzed by year. Vaccine coverage was about 50%; influenza vaccination uptake was independently associated with older age, male sex, increasing number of underlying chronic conditions, previous pneumococcal vaccination, annual expenses for specialist medical cares, and general practitioner to whom the elderly was in charge. After adjusting for previously described characteristics, vaccination was associated with lower mortality and influenza-related hospitalization rates. Specifically, during influenza season the adjusted incidence rate ratio of death and of influenza-related hospitalizations for vaccinated compared to unvaccinated persons was 0.63 [95% confidence interval (CI) 0.58–0.69, p < .001] and 0.86 (95% CI 0.81–0.91, p < .001), respectively. A similar effectiveness was estimated for death in all age groups (≤74, 75–84, ≥85 years old), whereas a higher effect was found for hospitalizations in subjects aged ≥75 years old. Vaccination was also effective both in males and females. Findings suggest a health benefit of the influenza vaccination in the elderly population. Efforts should be focused on strategies to increase the vaccination uptake as important instrument of prevention.

Impact of influenza vaccination on healthcare utilization - A systematic review

INTRODUCTION

Although a vaccine-preventable disease, influenza causes approximately 3-5 million cases of severe illness and about 290,000-650,000 deaths worldwide, which occur primarily among people 65 years and older. Nonetheless, prevention of influenza and its complications rely mainly on vaccination. We aimed to systematically evaluate influenza vaccine effectiveness at reducing healthcare utilization in older adults, defined as the reduction of outpatient visits, ILI and influenza hospitalizations, utilization of antibiotics and cardiovascular events by vaccination status during the influenza season.

METHODS

We searched MEDLINE, EMBASE, CINAHL, Cochrane Library and considered any seasonal influenza vaccine, excluding the pandemic (2009-10 season) vaccine. Reviewers independently assessed data extraction and quality assessment.

RESULTS

Of the 8308 citations retrieved, 22 studies were included in the systematic review. Overall, two studies (9%) were deemed at moderate risk of bias, thirteen (59%) at serious risk of bias and seven (32%) at critical risk of bias. For outpatient visits, we found modest evidence of protection by the influenza vaccine. For all-cause hospitalization outcomes, we found a wide range of results, mostly deemed at serious risk of bias. The included studies suggested that the vaccine may protect older adults against influenza hospitalizations and cardiovascular events. No article meeting our inclusion criteria explored the use of antibiotics and ILI hospitalizations. The high heterogeneity between studies hindered the aggregation of data into a meta-analysis.

CONCLUSION

The variability between studies prevented us from drawing a clear conclusion on the effectiveness of the influenza vaccine on healthcare utilization in older adults. Overall, the data suggests that the vaccine may result in a reduction of healthcare utilization in the older population. Further studies of higher quality are necessary.

A Community-Based Intervention for Improving Medication Adherence for Elderly Patients with Hypertension in Korea

The chronic disease management program, a community-based intervention including patient education, recall and remind service, and reduction of out-of-pocket payment, was implemented in 2005 in Korea to improve patients’ adherence for antihypertensive medications. This study aimed to assess the effect of a community-based hypertension intervention intended to enhance patient adherence to prescribed medications. This study applied a non-equivalent control group design using the Korean National Health Insurance Big Data. Hongcheon County has been continuously implementing the intervention program since 2012. This study involved a cohort of patients with hypertension aged >65 and <85 years, among residents who lived in the study area for five years (between 2010 and 2014). The final number of subjects was 2685 in both the intervention and control region. The indirect indicators were analyzed as patients’ adherence and level of continuous treatment using the difference-in-difference regression. The proportion of hypertensive patients who continuously received insurance benefits for >240 days in 2014 was 81.0% in the intervention region and 79.7% in the control region. The number of dispensations per prescription and the dispensation days per hypertensive patient in the intervention region increased by approximately 10.88% and 2.2 days on average by month, respectively, compared to those in the control region. The intervention program encouraged elderly patients with hypertension to receive continuous care. Another research is needed to determine whether further improvement in the continuity of comprehensive care will prevent the progression of cardiovascular diseases.

Effectiveness of a Hand Hygiene Program at Child Care Centers: A Cluster Randomized Trial

OBJECTIVES

Respiratory infections (RIs) are an important cause of morbidity and excessive antibiotic prescriptions in children attending day care centers (DCCs). We aimed to assess the effectiveness of an educational and hand hygiene program in DCCs and homes in reducing RI incidence and antibiotic prescriptions in children.

METHODS

A cluster, randomized, controlled, and open study of 911 children aged 0 to 3 years attending 24 DCCs in Almería (Spain) with an 8-month follow-up. Two intervention groups of DCC families performed educational and hand hygiene measures, 1 with soap and water (SWG; n = 274), another with hand sanitizer (HSG; n = 339), and the control group (CG; n = 298) followed usual hand-washing procedures. RI episode rates were compared through multilevel Poisson regression models. The percentage of days missed were compared with Poisson exact tests.

RESULTS

There were 5211 RI episodes registered. Children in the HSG had less risk of RI episodes (incidence rate ratio [IRR]: 0.77; 95% confidence interval [CI]: 0.68-0.88) and antibiotic prescriptions (IRR: 0.69; 95% CI: 0.57-0.84) compared with the those in the CG. Children in the SWG had a higher risk of RI episodes (IRR: 1.21; 95% CI: 1.06-1.39) and antibiotic prescriptions (IRR: 1.31; 95% CI: 1.08-1.56) than those in the HSG. Pupils missed 5186 DCC days because of RIs, and the percentage of days absent was significantly lower in the HSG compared with the CG (P < .001) and the SWG (P < .001).

CONCLUSIONS

Hand hygiene programs that include hand sanitizer and educational measures for DCC staff, children, and parents, reduce absent days, RIs, and antibiotic prescriptions for these infections in children at DCCs.

Effectiveness of seasonal influenza vaccination in patients with diabetes: protocol for a nested case-control study

INTRODUCTION

Seasonal influenza vaccination (SIV) is recommended for people with diabetes, but its effectiveness has not been demonstrated. All of the available studies are observational and marred with the healthy vaccine bias, that is, bias resulting from the generally better health behaviours practised by people who choose to be vaccinated against influenza, compared with those who do not. This protocol is intended to study the effectiveness of SIV in people with treated diabetes and simultaneously to control for bias.

METHODS AND ANALYSES

This case-control study is nested in a historical cohort and is designed to study vaccine effectiveness (VE) assessed by morbidity, mortality and anti-infective drug use. The cohort will comprise a representative sample of health insurance beneficiaries in France and will cover 10 consecutive epidemic seasons. It will include all patients reimbursed three separate times for drugs to treat diabetes. The first study of VE will use reasons for hospitalisation as the primary end point, and the second with the use of neuraminidase inhibitors and of antibiotics as the end points. A case will be defined as any person in the cohort reaching any end point at a given date. The case patient will be matched with the largest possible number of controls (individuals not reaching the end point by this date) according to the propensity score method with an optimal calliper width. A conditional logistic model will be used to estimate ORs to take into account both the matching and the repetition of measurements. The model will be applied separately during and outside of epidemic periods to estimate the residual confounding.

ETHICS AND DISSEMINATION

The study has been approved by the French Commission on Individual Data Protection and Public Liberties (ref: AT/CPZ/SVT/JB/DP/CR05222O). The study's findings will be published in peer-reviewed journals and disseminated at international conferences and through social media.

External adjustment of unmeasured confounders in a case-control study of benzodiazepine use and cancer risk

AIMS

Previous studies have reported diverging results on the association between benzodiazepine use and cancer risk.

METHODS

We investigated this association in a matched case-control study including incident cancer cases during 2002-2009 in the Danish Cancer Registry (n = 94 923) and age- and sex-matched (1:8) population controls (n = 759 334). Long-term benzodiazepine use was defined as ≥500 defined daily doses 1-5 years prior to the index date. We implemented propensity score (PS) calibration using external information on confounders available from a survey of the Danish population. Two PSs were used: The error-prone PS using register-based confounders and the calibrated PS based on both register- and survey-based confounders, retrieved from the Health Interview Survey.

RESULTS

Register-based data showed that cancer cases had more diagnoses, higher comorbidity score and more co-medication then population controls. Survey-based data showed lower self-rated health, more self-reported diseases, and more smokers as well as subjects with sedentary lifestyle among benzodiazepine users. By PS calibration, the odds ratio for cancer overall associated with benzodiazepine use decreased from 1.16 to 1.09 (95% confidence interval 1.00-1.19) and for smoking-related cancers from 1.20 to 1.10 (95% confidence interval 1.00-1.21).

CONCLUSION

We conclude that the increased risk observed in the solely register-based study could partly be attributed to unmeasured confounding.

Risk-adjusted procedure tailoring leads to uniformly low complication rates in ventral and incisional hernia repair: a propensity score analysis and internal validation of classification criteria

BACKGROUND

The usual approach in hernia surgery is to select the ideal repair method independent of the patient's characteristics. In the present study, we change the approach to ask which technique is best for the individual patient`s risk profile. For this, two criteria are important: does the patient need reconstruction of the abdominal wall? or does he or she need treatment of symptoms without being exposed to unnecessarily high perioperative risks?

METHODS

In a heuristic selection procedure, 486 consecutive patients were classified according to their characteristics as low-risk or high-risk for postoperative complications. Low-risk patients preferentially underwent open abdominal wall reconstruction with mesh (MFR + mesh), high-risk patients mainly a bridging-mesh procedure, either by laparoscopic (Lap.-IPOM) or open approach (Open-IPOM). Primary outcome was the incidence of postoperative complications. Secondary outcome was the recurrence-free interval. The propensity score was used for covariate adjustment analyzing recurrence rate as well as postoperative complications using Cox regression and logistic regression, respectively.

RESULTS

Comparison of all surgical procedures showed risk factors had no independent influence on occurrence of complications (p = 0.110). Hernial gap width was an independent factor for occurrence of complications (p = 0.002). Propensity score adjustment revealed Lap.-IPOM to have a significantly higher recurrence rate than MFR + mesh (HR 2.367, 95% CI 1.123-4.957, p = 0.024). Three or more risk factors were protective against recurrence (HR 0.454, 95% CI 0.221-0.924, p = 0.030). In the univariate Cox regression analysis for recurrence, age >50 years was a protective prognostic factor (HR 0.412, 95% CI 0.245-0.702, p = 0.002).

CONCLUSIONS

The classification criteria applied were internally validated. The heuristic algorithm ensured that patients at high-risk of complications did not have a higher perioperative complication rate than patients at low-risk.

Do influenza and pneumococcal vaccines prevent community-acquired respiratory infections among older people with diabetes and does this vary by chronic kidney disease? A cohort study using electronic health records

OBJECTIVE

We aimed to estimate the effectiveness of influenza and 23-valent pneumococcal polysaccharide vaccination on reducing the burden of community-acquired lower respiratory tract infection (LRTI) among older people with diabetes, and whether this varied by chronic kidney disease (CKD) status.

RESEARCH DESIGN AND METHODS

We used linked UK electronic health records for a retrospective cohort study of 190 492 patients ≥65 years with diabetes mellitus and no history of renal replacement therapy, 1997-2011. We included community-acquired LRTIs managed in primary or secondary care. Infection incidence rate ratios were estimated using the Poisson regression. Pneumococcal vaccine effectiveness (VE) was calculated as (1-effect measure). To estimate influenza VE, a ratio-of-ratios analysis (winter effectiveness/summer effectiveness) was used to address confounding by indication. Final VE estimates were stratified according to estimated glomerular filtration rate and proteinuria status.

RESULTS

Neither influenza nor pneumococcal vaccine uptake varied according to CKD status. Pneumococcal VE was 22% (95% CI 11% to 31%) against community-acquired pneumonia for the first year after vaccination, but was negligible after 5 years. In the ratio-of-ratios analysis, current influenza vaccination had 7% effectiveness for preventing community-acquired LRTI (95% CI 3 to 12). Pneumococcal VE was lower among patients with a history of proteinuria than among patients without proteinuria (p=0.04), but otherwise this study did not identify variation in pneumococcal or influenza VE by markers of CKD.

CONCLUSIONS

The public health benefits of influenza vaccine may be modest among older people with diabetes. Pneumococcal vaccination protection against community-acquired pneumonia declines swiftly: alternative vaccination schedules should be investigated.

Effectiveness of seasonal influenza vaccination in community-dwelling elderly people: an individual participant data meta-analysis of test-negative design case-control studies

BACKGROUND

Several aggregate data meta-analyses have provided estimates of the effectiveness of influenza vaccination in community-dwelling elderly people. However, these studies ignored the effects of patient-level confounders such as sex, age, and chronic diseases that could bias effectiveness estimates. We aimed to assess the confounder-adjusted effectiveness of influenza vaccines on laboratory-confirmed influenza among elderly people by conducting a global individual participant data meta-analysis.

METHODS

In this individual participant data meta-analysis, we considered studies included in a previously conducted aggregate data meta-analysis that included test-negative design case-control studies published up to July 13, 2014. We contacted all authors of the included studies on Dec 1, 2014, to request individual participant data. Patients were excluded if their unique identifier was missing, their vaccination status was unknown, their outcome status was unknown, or they had had suspected influenza infection more than once in the same influenza season. Cases were patients with influenza-like illness symptoms who tested positive for at least one of A H1N1, A H1N1 pdm09, A H3N2, or B viruses; controls were patients with influenza-like illness symptoms who tested negative for these virus types or subtypes. Influenza vaccine effectiveness against overall and subtype-specific laboratory-confirmed influenza were the primary and secondary outcomes. We used a generalised linear mixed model to calculate adjusted vaccine effectiveness according to vaccine match to the circulating strains of influenza virus and intensity of the virus activity (epidemic or non-epidemic). Vaccine effectiveness was defined as the relative reduction in risk of laboratory-confirmed influenza in vaccinated patients compared with unvaccinated patients. We did subgroup analyses to estimate vaccine effectiveness according to hemisphere, age category, and health status.

FINDINGS

We received 23 of the 53 datasets included in the aggregate data meta-analysis. Furthermore, six additional datasets were provided by data collaborators, which resulted in individual participant data for a total of 5210 participants. A total of 4975 patients had the required data for analysis. Of these, 3146 (63%) were controls and 1829 (37%) were cases. Influenza vaccination was significantly effective during epidemic seasons irrespective of vaccine match status (matched adjusted vaccine effectiveness 44·38%, 95% CI 22·63-60·01; mismatched adjusted vaccine effectiveness 20·00%, 95% CI 3·46-33·68; analyses in the imputed dataset). Seasonal influenza vaccination did not show significant effectiveness during non-epidemic seasons. We found substantial variation in vaccine effectiveness across virus types and subtypes, with the highest estimate for A H1N1 pdm09 (53·19%, 10·25-75·58) and the lowest estimate for B virus types (-1·52%, -39·58 to 26·16). Although we observed no significant differences between subgroups in each category (hemisphere, age, and health status), influenza vaccination showed a protective effect among elderly people with cardiovascular disease, lung disease, or aged 75 years and younger.

INTERPRETATION

Influenza vaccination is moderately effective against laboratory-confirmed influenza in elderly people during epidemic seasons. More research is needed to investigate factors affecting vaccine protection (eg, brand-specific or type-specific vaccine effectiveness and repeated annual vaccination) in elderly people.

FUNDING

University Medical Center Groningen.

Analysis of recruitment in a pragmatic observational study on C-reactive protein point-of-care testing in primary care

INTRODUCTION

Failure to recruit all eligible study patients can lead to biased results. Little is known on selective patient recruitment in studies on implementation of diagnostic devices.

OBJECTIVES

The aim of this observational study was to measure recruitment of patients in an implementation study in primary care on use of point-of-care (POC) C-reactive protein (CRP) and to evaluate recruitment bias and its impact on the study endpoint.

METHODS

In a cross-sectional observational study on POC CRP implementation and related antibiotics prescribing, we compared included patients with all eligible patients to assess the representativeness of the included subjects. Eligible patients were adults presenting with acute cough in primary care between March and September 2012. The frequency of POC CRP testing and the proportion of prescribed antibiotics were compared between recruited and non-recruited patients. As measure of bias, odds ratios (ORs) with accompanying 95% confidence intervals (CIs) for the association between CRP level (<20 mg/l or not) and antibiotic prescribing were computed.

RESULTS

Of all 1473 eligible patients 348 (24%) were recruited. In recruited patients, POC CRP tests were conducted and antibiotics prescribed more frequently as compared to non-recruited patients (81% versus 6% and 44% versus 29%, respectively). The ORs were 18.2 (95%CI: 9.6-34.3), 30.5 (95%CI: 13.2-70.3) and 3.8 (95%CI: 0.9-14.8) respectively in all eligible patients, the recruited and the non-recruited patients.

CONCLUSION

Selective recruitment resulted in an overestimation of POC CRP test use and antibiotic prescribing.

Longitudinal Trends in Hypertension Management and Mortality Among Octogenarians: Prospective Cohort Study

The role of hypertension management among octogenarians is controversial. In this long-term follow-up (>10 years) study, we estimated trends in hypertension prevalence, awareness, treatment, and control among octogenarians, and evaluated the relationship of systolic blood pressure (SBP) ranges with mortality. Data were based on the English Longitudinal Study of Ageing (ELSA). Outcome measures were hypertension prevalence, awareness, treatment and control, and cardiovascular disease, and all-cause mortality events. Participants were separated into 8 categories of SBP values (<110, 110-119, 120-129, 130-139, 140-149, 150-159, 160-169, and >169 mm Hg). Among 2692 octogenarians, mean SBP levels declined from 147 mm Hg in 1998/2000 to 134 mm Hg in 2012/2013. The decline was of lower magnitude in the 50 to 79 years old subgroup (n=22007). Hypertension prevalence and awareness were 40% and 13%, respectively, higher among octogenarians than the 50 to 79 years of age subgroup, but hypertension treatment rates were similar (≈90%). Around 47% of the treated octogenarians achieved conventional BP targets (<140/90 mm Hg), increasing to 59% when assessed against revised targets (<150/90 mm Hg). All-cause mortality rates were higher (hazard ratio, 1.55; 95% confidence interval, 0.89-2.72) at lower extremes of SBP values (<110 mm Hg). The lowest cardiovascular disease and all-cause mortality risk among treated octogenarians was observed for an SBP range of 140 to 149 mm Hg (1.04, 0.60-1.78) and 160 to 169 mm Hg (0.78, 0.51-1.21). An increasing trend in hypertension awareness and treatment was observed in a large sample of community-dwelling octogenarians. The results do not support the view that more stringent BP targets may be associated with lower mortality.

Effectiveness of influenza vaccination for preventing influenza-related complications in people with asthma: a systematic review protocol

INTRODUCTION

Influenza vaccination is administered annually as a preventive measure against influenza infection and influenza-related complications in high-risk individuals, such as those with asthma. However, the effectiveness of influenza vaccination in people with asthma against influenza-related complications is still not well established.

METHODS AND ANALYSIS

We will search the following databases: MEDLINE (Ovid), EMBASE (Ovid), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, Cochrane Database of Systematic Reviews (CDSR), Web of Science Core Collection, Science direct, WHO Library Information System (WHOLIS), Global Health Library and Chinese databases (CNKI, Wanfang and ChongQing VIP) from Jan 1970 to Jan 2016 for observational and experimental studies on effectiveness of influenza vaccine in people with asthma. The identification of studies will be complemented with the searching of the reference lists and citations, and contacting influenza vaccine manufacturers to identify unpublished or ongoing studies. Two reviewers will extract data and appraise the quality of each study independently. Separate meta-analyses will be undertaken for observational and experimental evidence using fixed-effect or random-effects models, as appropriate.

ETHICS AND DISSEMINATION

Formal ethical approval is not required, as primary data will not be collected. The review will be disseminated in peer-reviewed publications and conference presentations.

Frequency and impact of confounding by indication and healthy vaccinee bias in observational studies assessing influenza vaccine effectiveness: a systematic review

Background

Evidence on influenza vaccine effectiveness (VE) is commonly derived from observational studies. However, these studies are prone to confounding by indication and healthy vaccinee bias. We aimed to systematically investigate these two forms of confounding/bias.

Methods

Systematic review of observational studies reporting influenza VE and indicators for bias and confounding. We assessed risk of confounding by indication and healthy vaccinee bias for each study and calculated ratios of odds ratios (crude/adjusted) to quantify the effect of confounder adjustment. VE-estimates during and outside influenza seasons were compared to assess residual confounding by healthy vaccinee effects.

Results

We identified 23 studies reporting on 11 outcomes. Of these, 19 (83 %) showed high risk of bias: Fourteen due to confounding by indication, two for healthy vaccinee bias, and three studies showed both forms of confounding/bias. Adjustment for confounders increased VE on average by 12 % (95 % CI: 7–17 %; all-cause mortality), 9 % (95 % CI: 4–14 %; all-cause hospitalization) and 7 % (95 % CI: 4–10 %; influenza-like illness). Despite adjustment, nine studies showed residual confounding as indicated by significant off-season VE-estimates. These were observed for five outcomes, but more frequently for all-cause mortality as compared to other outcomes (p = 0.03) and in studies which indicated healthy vaccinee bias at baseline (p = 0.01).

Conclusions

Both confounding by indication and healthy vaccinee bias are likely to operate simultaneously in observational studies on influenza VE. Although adjustment can correct for confounding by indication to some extent, the resulting estimates are still prone to healthy vaccinee bias, at least as long as unspecific outcomes like all-cause mortality are used. Therefore, cohort studies using administrative data bases with unspecific outcomes should no longer be used to measure the effects of influenza vaccination.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1154-y) contains supplementary material, which is available to authorized users.

Influenza vaccine effectiveness estimates in Croatia in 2010-2011: a season with predominant circulation of A(H1N1)pdm09 influenza virus

This is a retrospective study using the test-negative case-control method to estimate seasonal 2010-2011 influenza vaccine effectiveness (VE) in Croatia. Of patients consulting a physician for influenza-like illness (ILI) and for whom a swab was taken, we compared RT-PCR influenza-positive and RT-PCR influenza-negative patients. We used a structured questionnaire and physicians' records to obtain information on vaccination status and potential confounders. We conducted a complete case analysis using logistic regression to measure adjusted VE overall, against A(H1N1)pdm09 and in age groups. Out of 785 interviewed patients, 495 eligible patients were included in the study, after applying exclusion criteria [217 cases, of which 92·6% were A(H1N1)pdm09 positive, 278 controls]. Crude VE was 31·9% [95% confidence interval (CI) -40·9 to 67·1] and adjusted VE was 20·7% (95% CI -71·4 to 63·3), with higher VE in youngest and oldest age groups. Results from this first VE study in Croatia suggest a low to moderate VE for the 2010-2011 season. Studies year on year are needed with a greater sample size to provide more precise estimates, and also by age group and risk groups for vaccination.

Methodological challenges in measuring vaccine effectiveness using population cohorts in low resource settings

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We discuss methodological challenges for evaluating vaccine effectiveness using cohorts.

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No single set of definitions or analytical approach can address all possible biases.

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Careful consideration of denominator, exposure and outcome definitions is needed.

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Sensitivity analyses are crucial to examine assumptions and explore subtle relationships.

Post-licensure real world evaluation of vaccine implementation is important for establishing evidence of vaccine effectiveness (VE) and programme impact, including indirect effects. Large cohort studies offer an important epidemiological approach for evaluating VE, but have inherent methodological challenges.

Since March 2012, we have conducted an open prospective cohort study in two sites in rural Malawi to evaluate the post-introduction effectiveness of 13-valent pneumococcal conjugate vaccine (PCV13) against all-cause post-neonatal infant mortality and monovalent rotavirus vaccine (RV1) against diarrhoea-related post-neonatal infant mortality. Our study sites cover a population of 500,000, with a baseline post-neonatal infant mortality of 25 per 1000 live births.

We conducted a methodological review of cohort studies for vaccine effectiveness in a developing country setting, applied to our study context. Based on published literature, we outline key considerations when defining the denominator (study population), exposure (vaccination status) and outcome ascertainment (mortality and cause of death) of such studies. We assess various definitions in these three domains, in terms of their impact on power, effect size and potential biases and their direction, using our cohort study for illustration. Based on this iterative process, we discuss the pros and cons of our final per-protocol analysis plan. Since no single set of definitions or analytical approach accounts for all possible biases, we propose sensitivity analyses to interrogate our assumptions and methodological decisions.

In the poorest regions of the world where routine vital birth and death surveillance are frequently unavailable and the burden of disease and death is greatest We conclude that provided the balance between definitions and their overall assumed impact on estimated VE are acknowledged, such large scale real-world cohort studies can provide crucial information to policymakers by providing robust and compelling evidence of total benefits of newly introduced vaccines on reducing child mortality.

Cardiovascular safety of sulphonylureas: over 40 years of continuous controversy without an answer

More than 40 years after publication of the University Group Diabetes Program trial, the cardiovascular safety of sulphonylureas is still contentious. Although several hypotheses linking sulphonylureas to adverse cardiovascular effects exist, none provide conclusive evidence. Adding to the controversy, current clinical trials and observational studies provide inconsistent, and sometimes conflicting, evidence for the cardiovascular effects of sulphonylureas. Overall, observational evidence suggests that an increased risk of adverse cardiovascular outcomes is associated with sulphonylureas; however, these data may be subject to residual confounding and bias. Although evidence from randomized controlled trials has suggested a neutral effect, the majority of these studies were not specifically designed to assess the effect of sulphonylureas on adverse cardiovascular event risk. Current ongoing large clinical trials may provide some clarity on the cardiovascular safety of sulphonylureas, but the results are not expected for several years. With the continued uncertainties concerning the cardiovascular safety of all antidiabetic drugs, a clear answer with regard to sulphonylureas is warranted. The objectives of the present article were to provide an overview of the controversy surrounding sulphonylurea-related cardiovascular effects, to discuss the limitations of the current literature, and to provide recommendations for future studies aiming to elucidate the true relationship between sulphonylureas and adverse cardiovascular effects in people with type 2 diabetes.

Vaccines for the prevention of seasonal influenza in patients with diabetes: systematic review and meta-analysis

BACKGROUND

Patients with diabetes are at increased risk of severe influenza disease; influenza vaccination for these patients is therefore recommended by the World Health Organization and several National Immunization Technical Advisory Groups. However, no systematic review has evaluated the effects of influenza vaccines for patients with diabetes.

METHODS

We conducted a systematic review and meta-analysis by searching Medline, Embase, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from inception until November 2014. We included all types of studies reporting on the efficacy, effectiveness, and/or safety of influenza vaccination in patients with type 1 and type 2 diabetes of all ages. We used the Newcastle-Ottawa scale to assess risk of bias in observational studies. Residual confounding was addressed by comparing estimates of vaccine effectiveness (VE) during influenza seasons to those obtained during off-seasons. Quality of the evidence for each outcome was assessed using the GRADE methodology.

RESULTS

Following review of 1,444 articles, 11 observational studies with a total of 170,924 participants were included. In diabetic patients of working-age (18-64 years), influenza vaccination prevented all-cause hospitalization with a pooled VE of 58% (95% CI, 6-81%) and hospitalization due to influenza or pneumonia (VE 43%; 95% CI, 28-54%), whereas no effects on all-cause mortality and influenza-like illness (ILI) were observed. In the elderly (65+), influenza vaccination prevented all-cause mortality (VE 38%; 95% CI, 32-43%), all-cause hospitalization (VE 23%; 95% CI, 1-40%), hospitalization due to influenza or pneumonia (VE 45%; 95% CI, 34-53%), and ILI (VE 13%; 95% CI, 10-16%). However, significant off-season estimates for several outcomes indicated residual confounding, particularly in elderly patients. Quality of the evidence was low to very low for all outcomes. Laboratory-confirmed influenza infections were not reported.

CONCLUSIONS

Due to strong residual confounding in most of the identified studies, the available evidence is insufficient to determine the magnitude of benefit that diabetic people derive from seasonal influenza vaccination. Adequately powered randomized controlled trials or quasi-experimental studies using laboratory-confirmed influenza-specific outcomes are urgently needed.

Effectiveness of seasonal influenza vaccine in community-dwelling elderly people: a meta-analysis of test-negative design case-control studies

BACKGROUND

The application of test-negative design case-control studies to assess the effectiveness of influenza vaccine has increased substantially in the past few years. The validity of these studies is predicated on the assumption that confounding bias by risk factors is limited by design. We aimed to assess the effectiveness of influenza vaccine in a high-risk group of elderly people.

METHODS

We searched the Cochrane library, Medline, and Embase up to July 13, 2014, for test-negative design case-control studies that assessed the effectiveness of seasonal influenza vaccine against laboratory confirmed influenza in community-dwelling people aged 60 years or older. We used generalised linear mixed models, adapted for test-negative design case-control studies, to estimate vaccine effectiveness according to vaccine match and epidemic conditions.

FINDINGS

35 test-negative design case-control studies with 53 datasets met inclusion criteria. Seasonal influenza vaccine was not significantly effective during local virus activity, irrespective of vaccine match or mismatch to the circulating viruses. Vaccination was significantly effective against laboratory confirmed influenza during sporadic activity (odds ratio [OR] 0·69, 95% CI 0·48-0·99) only when the vaccine matched. Additionally, vaccination was significantly effective during regional (match: OR 0·42, 95% CI 0·30-0·60; mismatch: OR 0·57, 95% CI 0·41-0·79) and widespread (match: 0·54, 0·46-0·62; mismatch: OR 0·72, 95% CI 0·60-0·85) outbreaks.

INTERPRETATION

Our findings show that in elderly people, irrespective of vaccine match, seasonal influenza vaccination is effective against laboratory confirmed influenza during epidemic seasons. Efforts should be renewed worldwide to further increase uptake of the influenza vaccine in the elderly population.

FUNDING

None.

The Vaccine Safety Datalink: successes and challenges monitoring vaccine safety

The Vaccine Safety Datalink (VSD) is a collaborative project between the Centers for Disease Control and Prevention (CDC) and 9 health care organizations. Established in 1990, VSD is a vital resource informing policy makers and the public about the safety of vaccines used in the United States. Large linked databases are used to identify and evaluate adverse events in over 9 million individuals annually. VSD generates rapid, important safety assessments for both routine vaccinations and emergency vaccination campaigns. VSD monitors safety of seasonal influenza vaccines in near-real time, and provided essential information on the safety of influenza A (H1N1) 2009 monovalent vaccine during the recent pandemic. VSD investigators have published important studies demonstrating that childhood vaccines are not associated with autism or other developmental disabilities. VSD prioritizes evaluation of new vaccines; searches for possible unusual health events after vaccination; monitors vaccine safety in pregnant women; and has pioneered development of biostatistical research methods.

Trimethoprim use before pregnancy and risk of congenital malformation: reanalyzed using a case-crossover design and a case-time-control design

PURPOSE

Studies on the safety of drugs used during pregnancy are necessary and important but prone to bias. Using cases as their own controls can reduce bias. We used a case-crossover design and a case-time-control design to estimate the risk of congenital malformation (CM) for children born to mothers who redeemed a trimethoprim prescription shortly before pregnancy.

METHODS

The study was based on all live born singletons (N = 685 600) in Denmark whose mothers had available information on prescriptions in the Danish National Prescription Registry between 1996 and 2008. We defined 1-3 months before pregnancy as a potential risk period and 13-15 months before pregnancy as a reference period. Two other reference periods were used (7-9 months before pregnancy and months 4-6 of pregnancy). The case-crossover design is dependent on the assumption of a stable trimethoprim prescription over the study period in the source population. To estimate the trend of trimethoprim prescriptions, we used a control group comprising children without CMs.

RESULTS

Both study designs showed children had a higher risk of overall CM [odds ratio of 1.66, 95% confidence interval (CI): 1.10-2.53 and 1.50, 95%CI: 0.66-3.38, respectively] if their mothers had a trimethoprim prescription in the 3 months before pregnancy and subtypes of CM for example in the musculoskeletal system, which were consistent to the previous findings from a cohort study.

CONCLUSIONS

This study corroborates that trimethoprim is a potential teratogen when used 3 months before pregnancy and demonstrates the value of case-only approaches for studying, for example, adverse effects of antibiotics in reproductive epidemiology.

Influenza vaccination and fetal and neonatal outcomes

As pregnant women are considered a high-risk group for severe influenza illness, current recommendations advise vaccination of all pregnant women with inactivated influenza vaccine. Nevertheless, rates of maternal influenza vaccination have historically been low, possibly reflecting ongoing concerns about vaccine safety. Until recently, the majority of evidence concerning safety of influenza vaccination during pregnancy was limited to post-marketing pharmacovigilance studies; however, in the past 5 years, one randomized clinical trial and a number of observational studies reflecting seasonal trivalent inactivated influenza vaccines and monovalent H1N1 influenza vaccines have been published. This review summarizes the evidence pertaining to fetal and neonatal outcomes following influenza vaccination during pregnancy for comparative analytic studies published between 2008 and August 2013. Since the majority of these studies are observational in nature, issues related to study quality are also addressed.

After adjusting for bias in meta-analysis seasonal influenza vaccine remains effective in community-dwelling elderly

OBJECTIVE

To compare the performance of the bias-adjusted meta-analysis to the conventional meta-analysis assessing seasonal influenza vaccine effectiveness among community-dwelling elderly aged 60 years and older.

STUDY DESIGN AND SETTING

Systematic literature search revealed 14 cohort studies that met inclusion and exclusion criteria. Laboratory-confirmed influenza, influenza-like illness, hospitalization from influenza and/or pneumonia, and all-cause mortality were study outcomes. Potential biases were identified using bias checklists. The magnitude and uncertainty of biases were assessed by expert opinion. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using random effects model.

RESULTS

After incorporating biases, overall effect estimates regressed slightly toward no effect, with the largest relative difference between conventional and bias-adjusted ORs for laboratory-confirmed influenza (OR, 0.18; 95% CI: 0.01, 3.00 vs. OR, 0.23; 95% CI: 0.03, 2.04). In most of the studies, CIs widened reflecting uncertainties about the biases. The between-study heterogeneity reduced considerably with the largest reduction for all-cause mortality (I(2) = 4%, P = 0.39 vs. I(2) = 91%, P < 0.01).

CONCLUSION

This case study showed that after addressing potential biases influenza vaccine was still estimated effective in preventing hospitalization from influenza and/or pneumonia and all-cause mortality. Increasing the number of assessors and incorporating empirical evidence might improve the new bias-adjustment method.

Methodological quality of systematic reviews on influenza vaccination

BACKGROUND

There is a growing body of evidence on the risks and benefits of influenza vaccination in various target groups. Systematic reviews are of particular importance for policy decisions. However, their methodological quality can vary considerably.

OBJECTIVES

To investigate the methodological quality of systematic reviews on influenza vaccination (efficacy, effectiveness, safety) and to identify influencing factors.

METHODS

A systematic literature search on systematic reviews on influenza vaccination was performed, using MEDLINE, EMBASE and three additional databases (1990-2013). Review characteristics were extracted and the methodological quality of the reviews was evaluated using the assessment of multiple systematic reviews (AMSTAR) tool. U-test, Kruskal-Wallis test, chi-square test, and multivariable linear regression analysis were used to assess the influence of review characteristics on AMSTAR-score.

RESULTS

Fourty-six systematic reviews fulfilled the inclusion criteria. Average methodological quality was high (median AMSTAR-score: 8), but variability was large (AMSTAR range: 0-11). Quality did not differ significantly according to vaccination target group. Cochrane reviews had higher methodological quality than non-Cochrane reviews (p=0.001). Detailed analysis showed that this was due to better study selection and data extraction, inclusion of unpublished studies, and better reporting of study characteristics (all p<0.05). In the adjusted analysis, no other factor, including industry sponsorship or journal impact factor had an influence on AMSTAR score.

CONCLUSIONS

Systematic reviews on influenza vaccination showed large differences regarding their methodological quality. Reviews conducted by the Cochrane collaboration were of higher quality than others. When using systematic reviews to guide the development of vaccination recommendations, the methodological quality of a review in addition to its content should be considered.

Seasonal Influenza Vaccine Effectiveness (SIVE): an observational retrospective cohort study – exploitation of a unique community-based national-linked database to determine the effectiveness of the seasonal trivalent influenza vaccine

Background

Globally, seasonal influenza is responsible for an estimated 3 to 5 million cases of severe illness and 250,000 to 500,000 deaths per year. It is uncertain to what extent national vaccination programmes can prevent this morbidity and mortality.

Objective

To determine the effectiveness of the seasonal trivalent inactivated influenza vaccine.

Design

We undertook a retrospective observational cohort study. A propensity score model was constructed and adjusted odds ratios (ORs) were calculated to assess differences in vaccine uptake according to a number of patient characteristics. Adjusted illness and mortality hazard ratios (HRs) were estimated from a Cox proportional hazards model adjusted for sex, age, socioeconomic status, smoking status, urban/rural location, clinical at-risk groups (i.e. patients with chronic respiratory, heart, kidney, liver or neurological disease, immunosuppression and diabetes), Charlson comorbidity index, previous pneumococcal and influenza vaccination, and number of previous primary care consultations, prescribed drugs and hospital admissions. We also included nursing home residence and social care support. Vaccine effectiveness (VE) was expressed as a percentage, and represents a reduction in risk provided by the vaccine for a given outcome (e.g. laboratory-confirmed influenza). This was calculated as 1 − HR, where HR is that of the measured clinical outcome in vaccinated compared with unvaccinated individuals. For estimates of VE derived from linked virological swab data, we carried out a nested case–control study design.

Setting

A national linkage of patient-level primary care, hospital, death certification and virological swab-linked data across nine influenza seasons (2000–9).

Participants

A nationally representative sample of the Scottish population during 1,767,919 person-seasons of observation. Cases of influenza were confirmed using reverse transcription-polymerase chain reaction (RT-PCR) in a subset of the population (n = 3323).

Interventions

Trivalent inactivated seasonal influenza vaccination (n = 274,071).

Main outcome measures

VE, pooled across seasons and adjusting for confounders, was estimated by determining laboratory-confirmed influenza, influenza-related morbidity and mortality including primary care influenza-like illnesses, hospitalisation and death from influenza and pneumonia.

Results

Most vaccines (93.6%;n = 256,474 vaccines) were administered to at-risk patients targeted for vaccination, with a 69.3% uptake among those aged ≥ 65 years (178,754 vaccinations during 258,100 person-seasons). For at-risk patients aged < 65 years there was a 26.2% uptake (77,264 vaccinations during 295,116 person-seasons). VE in preventing RT-PCR laboratory-confirmed influenza was 57.1% [95% confidence interval (CI) 31.3% to 73.3%]. VE was 18.8% (95% CI –103.7% to 67.6%) in patients aged ≥ 65 years and 59.6% (95% CI 21.9% to 79.1%) in those aged < 65 years at risk of serious complications from influenza. In the matched analysis (156,096 person-seasons), adjusted VE for reducing primary care consultations for influenza-like illnesses was 16.3% (95% CI 5.7% to 26.0%). VE in reducing hospitalisations was 19.3% for influenza and pneumonia (95% CI 8.3% to 29.1%) and 26.7% for pneumonia and chronic obstructive pulmonary disease (95% CI 19.8% to 32.9%). VE in reducing death due to influenza and pneumonia was 37.9% (95% CI 29.5% to 45.4%).

Conclusions

Few countries' health systems allow for the integrated and accessible data recording that made this study possible and made it feasible to collate centrally almost all hospitalisations and deaths attributed to influenza, thereby allowing completeness of reporting. Using these data, we found most influenza vaccines were administered to those at risk of serious complications from influenza. In a nationally representative cohort we found that the vaccine was associated with a significant decrease in the risk of RT-PCR-confirmed influenza (the decrease was substantial particularly for at-risk patients aged < 65 years) and complications arising from influenza (where more modest decreases were found). Although the modest size of our cohort made it possible to collate centrally almost all cases of influenza-related disease, analysis of subgroups (in particular older age groups) or by individual season resulted in poorer precision and wide CIs. Any future work should therefore aim to address this issue by ensuring adequate power to test VE in these subgroups of patients, while minimising the effect of bias, such as health-seeking behaviour.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Effectiveness of pneumococcal conjugate vaccine in infants by maternal influenza vaccination status

BACKGROUND

Influenza virus infection can predispose patients to secondary pneumococcal infections. Children are at greatest risk for pneumococcal infection in the first year of life and are not considered fully protected by pneumococcal conjugate vaccine (PCV) until their third dose at 6 months of age. Infants less than 6 months cannot receive influenza vaccination, though maternal influenza vaccination can protect infants.

METHODS

We conducted a retrospective cohort study of 9807 mother-infant pairs enrolled in a managed care organization for infants born June 1, 2002, to December 31, 2009. Exposure was assessed for receipt of infant PCV only and the combination of PCV and maternal influenza vaccine (trivalent inactivated vaccine). Outcomes of interest were acute otitis media and medically attended acute respiratory infection in the first year of life. We estimated the adjusted incidence of illness, incidence rate ratios and vaccine effectiveness using the ratio of incidence rate ratios between the periods of noncirculating influenza and that of at least local influenza circulation.

RESULTS

For medically attended acute respiratory infection, vaccine effectiveness for the combination of trivalent inactivated vaccine and PCV was 39.6% (95% confidence interval [CI]: 31.6%-46.7%) and for PCV only was 29.8% (95% CI: 11.4%-44.3%). For acute otitis media, vaccine effectiveness for the combination of trivalent inactivated vaccine and PCV was 47.9% (95% CI: 42%-53.3%) and for PCV only was 37.6% (95% CI: 23.1%-49.4%).

CONCLUSION

In infants, the combination of maternal influenza vaccine and infant pneumococcal conjugate vaccination confers greater protection from acute otitis media infections and medically attended acute respiratory infections than does PCV alone.

Further evidence for bias in observational studies of influenza vaccine effectiveness: the 2009 influenza A(H1N1) pandemic

Preinfluenza periods have been used to test for uncontrolled confounding in studies of influenza vaccine effectiveness, but some authors have claimed that confounding differs in preinfluenza and influenza periods. We tested this claim by comparing estimates of the vaccine-mortality association during the 2009/2010 influenza year, when there was essentially no circulation of seasonal influenza in the United States, and 2007/2008, a typical influenza year. We pooled data on seniors (adults aged ≥65 years) from 7 US managed care organizations that participated in the Vaccine Safety Datalink Project. We defined influenza vaccination, all-cause mortality, and potential confounders from administrative databases. We quantified the vaccine-mortality association using Cox regression. During 2007/2008, the adjusted hazard ratio was 0.44 prior to influenza season, 0.62 during influenza season, and 0.71 after influenza season. A similar pattern was observed during 2009/2010, when any effect of seasonal influenza vaccine observed during all time periods must have resulted from confounding: 0.65 during the autumn, 0.80 during the winter, and 0.84 during the summer. In a year with minimal seasonal influenza, we found no evidence that confounding in autumn preinfluenza periods is qualitatively different from confounding in winter. This supports the use of preinfluenza periods as control time periods in studies of influenza vaccine effectiveness.

Estimating vaccine effectiveness against severe influenza in England and Scotland 2011/2012: applying the screening method to data from intensive care surveillance systems

Methods for estimating vaccine effectiveness (VE) against severe influenza are not well established. We used the screening method to estimate VE against influenza resulting in intensive care unit (ICU) admission in England and Scotland in 2011/2012. We extracted data on confirmed influenza ICU cases from severe influenza surveillance systems, and obtained their 2011/2012 trivalent influenza vaccine (TIV) status from primary care. We compared case vaccine uptake with population vaccine uptake obtained from routine monitoring systems, adjusting for age group, specific risk group, region and week. Of 60 influenza ICU cases reported, vaccination status was available for 56 (93%). Adjusted VE against ICU admission for those aged ≥ 65 years was -10% [95% confidence interval (CI) -207 to 60], consistent with evidence of poor protection from the 2011/2012 TIV in 2011/2012. Adjusted VE for those aged <65 years in risk groups was -296% (95% CI -930 to -52), suggesting significant residual confounding using the screening method in those subject to selective vaccination.

Mortality in members of HIV-1 serodiscordant couples in Africa and implications for antiretroviral therapy initiation: results of analyses from a multicenter randomized trial

Background

The risk of HIV-1 related mortality is strongly related to CD4 count. Guidance on optimal timing for initiation of antiretroviral therapy (ART) is still evolving, but the contribution of HIV-1 infection to excess mortality at CD4 cell counts above thresholds for HIV-1 treatment has not been fully described, especially in resource-poor settings. To compare mortality among HIV-1 infected and uninfected members of HIV-1 serodiscordant couples followed for up to 24 months, we conducted a secondary data analysis examining mortality among HIV-1 serodiscordant couples participating in a multicenter, randomized controlled trial at 14 sites in seven sub-Saharan African countries.

Methods

Predictors of death were examined using Cox regression and excess mortality by CD4 count and plasma HIV-1 RNA was computed using Poisson regression for correlated data.

Results

Among 3295 HIV serodiscordant couples, we observed 109 deaths from any cause (74 deaths among HIV-1 infected and 25 among HIV-1 uninfected persons). Among HIV-1 infected persons, the risk of death increased with lower CD4 count and higher plasma viral levels. HIV-1 infected persons had excess mortality due to medical causes of 15.2 deaths/1000 person years at CD4 counts of 250 – 349 cells/μl and 8.9 deaths at CD4 counts of 350 – 499 cells/μl. Above a CD4 count of 500 cells/μl, mortality was comparable among HIV-1 infected and uninfected persons.

Conclusions

Among African serodiscordant couples, there is a high rate of mortality attributable to HIV-1 infection at CD4 counts above the current threshold (200 – 350 cells/μl) for ART initiation in many African countries. These data indicate that earlier initiation of treatment is likely to provide clinical benefit if further expansion of ART access can be achieved.

Trial Registration

Clinicaltrials.gov (NCT00194519)

Effectiveness of an influenza A (H1N1) 2009 monovalent vaccine among Japanese pregnant women: a prospective observational study assessing antibody efficacy

In order to estimate the effectiveness of an influenza A (H1N1) 2009 monovalent vaccine among pregnant women, we prospectively observed 135 Japanese pregnant women who received an influenza A (H1N1) 2009 monovalent vaccine during November 2009. We calculated an index of "antibody efficacy", in which the medical visits for respiratory illnesses were compared between those with and without post-vaccination hemagglutination inhibition (HI) titer ≥1:40. The product of antibody efficacy and achievement rate is theoretically equivalent to the vaccine effectiveness. Among all subjects, an inverse but non-significant relationship during the epidemic period was observed between post-vaccination HI titer ≥1:40 and medical visits for respiratory illnesses. After stratification by trimester at recruitment, a significant inverse association during the epidemic period was found among subjects in the first or second trimester (antibody efficacy: 91%, vaccine effectiveness: 79%). The influenza A (H1N1) 2009 monovalent vaccine administered in the first or second trimester reduced medical visits for respiratory illnesses among Japanese pregnant women.

Effectiveness of adjuvanted influenza vaccination in elderly subjects in northern Italy

Although vaccination against influenza is recommended for elderly and high-risk patients in many countries, efficacy in the elderly has been suboptimal. The MF59 adjuvanted trivalent inactivated vaccine (ATIV) was developed to increase the immune response of elderly subjects to influenza vaccination, but its effectiveness has not yet been well documented. This prospective, observational study evaluated the relative effectiveness of ATIV versus nonadjuvanted trivalent inactivated vaccine (TIV) in individuals at least 65 years of age in Lombardy, northern Italy. Hospitalizations for influenza or pneumonia (International Classification of Diseases, Ninth Revision, Clinical Modification, codes 480–487) during the 2006–2007, 2007–2008, and 2008–2009 influenza seasons were identified from administrative databases. Stratified and regression analyses, including the propensity score to adjust for confounding, as well as generalized estimating equations to account for repeated vaccination, were used. Overall, 107,661 records were evaluated, contributing 170,988 person-seasons of observation. Since ATIV is preferentially recommended for more frail individuals, subjects vaccinated with ATIV were older and had more functional impairment and comorbidities. In the primary analysis, risk of hospitalization for influenza or pneumonia was 25% lower for ATIV relative to TIV (relative risk = 0.75, 95% confidence interval: 0.57, 0.98). To the extent that there is residual bias, ATIV is likely to be even more protective than this result suggests.

Factors influencing choice of surgical route of repair of genitourinary fistula, and the influence of route of repair on surgical outcomes: findings from a prospective cohort study

OBJECTIVE

The abdominal route of genitourinary fistula repair may be associated with longer term hospitalisation, hospital-associated infection and increased resource requirements. We examined: (1) the factors influencing the route of repair; (2) the influence of the route of repair on fistula closure 3 months following surgery; and (3) whether the influence of the route of repair on repair outcome varied by whether or not women met the published indications for abdominal repair.

DESIGN

Prospective cohort study.

SETTING

Eleven health facilities in sub-Saharan Africa and Asia.

POPULATION

The 1274 women with genitourinary fistula presenting for surgical repair services.

METHODS

Risk ratios (RRs) and 95% confidence intervals (95% CIs) were generated using log-binomial and Poisson (log-link) regression. Multivariable regression and propensity score matching were employed to adjust for confounding.

MAIN OUTCOME MEASURES

Abdominal route of repair and fistula closure at 3 months following fistula repair surgery.

RESULTS

Published indications for abdominal route of repair (extensive scarring or tissue loss, genital infibulation, ureteric involvement, trigonal, supratrigonal, vesico-uterine or intracervical location or other abdominal pathology) predicted the abdominal route [adjusted risk ratio (ARR), 15.56; 95% CI, 2.12-114.00]. A vaginal route of repair was associated with increased risk of failed closure (ARR, 1.41; 95% CI, 1.05-1.88); stratified analyses suggested elevated risk among women meeting indications for the abdominal route.

CONCLUSIONS

Additional studies powered to test effect modification hypotheses are warranted to confirm whether the abdominal route of repair is beneficial for certain women.

The potential effect of temporary immunity as a result of bias associated with healthy users and social determinants on observations of influenza vaccine effectiveness; could unmeasured confounding explain observed links between seasonal influenza vaccine and pandemic H1N1 infection?

BACKGROUND

Five observational studies from Canada found an association between seasonal influenza vaccine receipt and increased risk of pandemic influenza H1N1 2009 infection. This association remains unexplained. Although uncontrolled confounding has been suggested as a possible explanation, the nature of such confounding has not been identified. Observational studies of influenza vaccination can be affected by confounding due to healthy users and the influence of social determinants on health. The purpose of this study was to investigate the influence that these two potential confounders may have in combination with temporary immunity, using stratified tables. The hypothesis is that respiratory virus infections may activate a temporary immunity that provides short-term non-specific protection against influenza and that the relationship with being a healthy user or having a social determinant may result in confounding.

METHODS

We simulated the effect of confounding on vaccine effectiveness assuming that this could result from both social determinants and healthy user effects as they both influence the risk of seasonal influenza and non-influenza respiratory virus infections as well as the likelihood of being vaccinated. We then examined what impact this may have had on measurement of seasonal influenza vaccine effectiveness against pandemic influenza.

RESULTS

In this simulation, failure to adjust for healthy users and social determinants would result in an erroneously increased risk of pandemic influenza infection associated with seasonal influenza vaccination. The effect sizes were not however large.

CONCLUSIONS

We found that unmeasured healthy user effects and social determinants could result in an apparent association between seasonal influenza vaccine and pandemic influenza infection by virtue of being related to temporary immunity. Adjustment for social determinants of health and the healthy user effects are required in order to improve the quality of observational studies of influenza vaccine effectiveness.

Additive benefits of pneumococcal and influenza vaccines among elderly persons aged 75 years or older in Taiwan--a representative population-based comparative study

OBJECTIVE

It remains unclear whether pneumococcal vaccine provides additional protection to the elderly who have already vaccinated with influenza vaccine. This retrospective cohort study aimed to assess the additive effect of pneumococcal and influenza vaccines on the risk of mortality, hospitalization, and inpatient expenditure in the elderly aged 75 years or older in Taiwan.

METHODS

Data were extracted from the National Health Insurance claims data of a nationally representative elderly sample. To reduce potential selection bias, we employed a propensity score matching method to classify the vaccination status into 3 groups. Multivariable logistic and linear regression models were used to compare the outcomes among different groups.

RESULTS

Each group contained 8142 subjects. The results indicated that an additive effect of receiving both vaccines was associated with a significantly lower all-cause mortality (relative risk [RR]: 0.74; 95% confidence interval [CI]: 0.57-0.96), hospitalization of all diseases including pneumonia, influenza, chronic obstructive pulmonary disease, respiratory diseases, and congestive heart disease (RR: 0.77; 95% CI: 0.67-0.90), and a 13% reduction (95% CI: 0.81-0.94) in inpatient expenditures of all diseases when compared with receiving influenza vaccine alone.

CONCLUSIONS

This study confirmed that vaccination of elderly individuals with pneumococcal vaccine and influenza vaccine concomitantly has substantial beneficial effects.

The risk of Guillain-Barré syndrome associated with influenza A (H1N1) 2009 monovalent vaccine and 2009-2010 seasonal influenza vaccines: results from self-controlled analyses

PURPOSE

The Centers for Disease Control and Prevention Emerging Infections Program implemented active, population-based surveillance for Guillain-Barré syndrome (GBS) following H1N1 vaccines in 10 states/metropolitan areas. We report additional analyses of these data using self-controlled methods, which avoid potential confounding from person-level factors and co-morbidities.

METHODS

Surveillance officers identified GBS cases with symptom onset during October 2009-April 2010 and ascertained receipt of H1N1 vaccines. We calculated self-controlled relative risks by comparing the number of cases with onset during a risk interval 1-42 days after vaccination with cases with onset during fixed (days 43-84) or variable (days 43-end of study period) control intervals. We calculated attributable risks by applying statistically significant relative risks to an independent estimate of GBS incidence.

RESULTS

Fifty-nine GBS cases received H1N1 vaccine with or without seasonal vaccine. The relative risk was 2.1 (95%CI 1.2, 3.5) by the variable-window and 3.0 (95%CI 1.4, 6.4) by the fixed-window analyses. The corresponding attributable risks per million doses administered were 1.5 (95%CI 0.3, 3.4) and 2.8 (95%CI 0.6, 7.4).

CONCLUSIONS

These attributable risks are similar to those of some previous formulations of seasonal influenza vaccine (about one to two cases per million doses administered), suggesting a low risk of GBS following the H1N1 vaccine that is not clearly higher than that of seasonal influenza vaccines.

Effectiveness of influenza vaccine in aging and older adults: comprehensive analysis of the evidence

Foremost amongst the diseases preventable by vaccination is influenza. Worldwide, influenza virus infection is associated with serious adverse events leading to hospitalization, debilitating complications, and death in elderly individuals. Immunization is considered to be the cornerstone for preventing these adverse health outcomes, and vaccination programs are timed to optimize protection during the annual influenza season. Trivalent inactivated influenza virus vaccines are believed to be both effective and cost-saving; however, in spite of widespread influenza vaccination programs, rates of hospitalization for acute respiratory illness and cardiovascular diseases have been increasing in this population during recent annual influenza seasons. From meta-analyses summarizing estimates of influenza vaccine effectiveness from available observational clinical studies, this review aims to examine how effective current influenza vaccine strategies are in the aging and older adult population and to analyze which are the most important biases that interfere with measurements of influenza vaccine effectiveness. Furthermore, consideration is given to strategies that should be adopted in order to optimize influenza vaccine effectiveness in the face of immune exhaustion.

Effectiveness of seasonal influenza vaccine against pandemic (H1N1) 2009 virus, Australia, 2010

To estimate effectiveness of seasonal trivalent and monovalent influenza vaccines against pandemic influenza A (H1N1) 2009 virus, we conducted a test-negative case–control study in Victoria, Australia, in 2010. Patients seen for influenza-like illness by general practitioners in a sentinel surveillance network during 2010 were tested for influenza; vaccination status was recorded. Case-patients had positive PCRs for pandemic (H1N1) 2009 virus, and controls had negative influenza test results. Of 319 eligible patients, test results for 139 (44%) were pandemic (H1N1) 2009 virus positive. Adjusted effectiveness of seasonal vaccine against pandemic (H1N1) 2009 virus was 79% (95% confidence interval 33%–93%); effectiveness of monovalent vaccine was 47% and not statistically significant. Vaccine effectiveness was higher among adults. Despite some limitations, this study indicates that the first seasonal trivalent influenza vaccine to include the pandemic (H1N1) 2009 virus strain provided significant protection against laboratory-confirmed pandemic (H1N1) 2009 infection.

Seasonal Influenza Vaccine Effectiveness in the community (SIVE): protocol for a cohort study exploiting a unique national linked data set

INTRODUCTION

Seasonal influenza vaccination is recommended for all individuals aged 65 years and over and in individuals younger than 65 years with comorbidities. There is good evidence of vaccine effectiveness (VE) in young healthy individuals but less robust evidence for effectiveness in the populations targeted for influenza vaccination. Undertaking a randomised controlled trial to assess VE is now impractical due to the presence of national vaccination programmes. Quasi-experimental designs offer the potential to advance the evidence base in such scenarios, and the authors have therefore been commissioned to undertake a naturalistic national evaluation of seasonal influenza VE by using data derived from linkage of a number of Scottish health databases. The aim of this study is to examine the effectiveness of the seasonal influenza vaccination in the Scottish population.

METHODS AND ANALYSIS

A cohort study design will be used pooling data over nine seasons. A primary care database covering 4% of the Scottish population for the period 2000-2009 has been linked to the national database of hospital admissions and the death register and is being linked to the Health Protection Scotland virology database. The primary outcome is VE measured in terms of rate of hospital admissions due to respiratory illness. Multivariable regression will be used to produce estimates of VE adjusted for confounders. The major challenge of this approach is addressing the strong effect of confounding due to vaccinated individuals being systematically different from unvaccinated individuals. Analyses using propensity scores and instrumental variables will be undertaken, and the effect of an unknown confounder will be modelled in a sensitivity analysis to assess the robustness of the estimates.

ETHICS AND DISSEMINATION

The West of Scotland Research Ethics Committee has classified this project as surveillance. The study findings will be disseminated in peer-reviewed publications and presented at international conferences.