Prevention and Control of Seasonal Influenza With Vaccines: Recommendations of the Advisory Committee on Immunization Practices-United States, 2017-18 Influenza Season

Knowledge, Attitude, and Barriers Influencing Seasonal Influenza Vaccination Uptake

Background

Seasonal influenza is an acute respiratory infection caused by influenza viruses that are highly contagious and circulate in all parts of the world. It gives rise to an estimated 3 to 5 million cases of severe illness and about 250,000 to 500,000 deaths globally each year. Influenza tends to cause epidemics with serious illness and death among high-risk groups such as children aged 5 years and younger, pregnant women, elderly ≥65 years of age, and with chronic medical conditions. According to the Centers for Disease Prevention and Control (CDC), all people who are 6 months old and above are recommended to receive the seasonal influenza vaccine annually. Despite the fact that influenza vaccine is readily available, and the severity of the disease is known to adversely affect the individual's quality of life and well-being, vaccination uptake rates are still low, contributing to the increased burden of the disease worldwide.

Objectives

To measure the influenza vaccine uptake among residents of Riyadh Province, Saudi Arabia, that determines their attitude, knowledge, and beliefs regarding the vaccine.

Methods

A cross-sectional study was conducted using a self-administered structured questionnaire distributed online targeting residents of Riyadh Province, Saudi Arabia, from 1st of August 2019 till 30th of September 2019. Participants were selected through volunteer sampling. The questionnaire included demographic data including age, gender, occupation, education level, marital status, and comorbidities. It also included questions regarding knowledge, attitude, and beliefs regarding influenza vaccine. After collection of data, statistical analyses were conducted by using Statistical Package for Social Sciences (SPSS) version 19.0. A P value of <0.05 was considered statistically significant.

Results

Our study included 503 participants, with age ranging from 18 to 65 years old and 324 (64%) were females. 100 participants (19.9%) had comorbid conditions, and 223 (44.3%) have been vaccinated against influenza in the past. A large portion of participants (41.2%) were familiar with seasonal influenza vaccination from the media. The knowledge part of the questionnaire showed that 302 (60%) participants knew how often they should receive the vaccine and 313 (62.2%) participants knew that the vaccine is provided freely in all of Saudi Arabia. In terms of belief and attitude, 371 participants (73.8%) thought they were susceptible to the disease and 365 (73.8%) believed that influenza vaccine is beneficial, while 446 participants (88.7%) thought that the general public need more knowledge and awareness on the scientific facts of influenza vaccine. Regarding barriers, 295 participants (58.6%) wanted to avoid vaccines and 252 (50.1%) were concerned about the vaccine's adverse effects. Participants with frequent health checkups and those who had previous knowledge on the availability of the vaccine for free were more likely to be vaccinated. Vaccinated participants (44.3%) were asked if they were willing to take the vaccine again when it is due, 158 (70.9%) answered yes. Those who elicited symptomatic reaction to the vaccine (26.0%) were less inclined to take it again (P = 0.035).

Conclusion

We concluded that there is a low influenza vaccine uptake rate among our study population, considering that the barriers most commonly chosen by participants are solvable with health education and campaigns oriented towards delivering facts about the vaccine and dispelling misinformation; such measures are highly recommended and are postulated to carry a great benefit that should target common misconceptions identified in this study.

Immunogenicity of seasonal inactivated influenza and inactivated polio vaccines among children in Senegal: Results from a cluster-randomized trial

Data on influenza vaccine immunogenicity in children are limited from tropical developing countries. We recently reported significant, moderate effectiveness of a trivalent inactivated influenza vaccine (IIV) in a controlled, cluster-randomized trial in children in rural Senegal during 2009, a year of H3N2 vaccine mismatch (NCT00893906). We report immunogenicity of IIV3 and inactivated polio vaccine (IPV) from that trial. We evaluated hemagglutination inhibition (HAI) and polio antibody titers in response to vaccination of three age groups (6 through 35 months, 3 through 5 years, and 6 through 8 years). As all children were IIV naïve, each received two vaccine doses, although titers were assessed after only the first dose for subjects aged 6 through 8 years. Seroconversion rates (4-fold titer rise or increase from <1:10 to ≥1:40) were 74-87% for A/H1N1, 76-87% for A/H3N2, and 54-79% for B/Yamagata. Seroprotection rates (HAI titer ≥ 1:40) were 79-88% for A/H1N1, 88-96% for A/H3N2, and 52-74% for B/Yamagata. IIV responses were lowest in the youngest age group, and they were comparable between ages 3 through 5 years after two doses and 6 through 8 years after one dose. We found that baseline seropositivity (HAI titer ≥ 1:10) was an effect modifier of IIV response. Using a seroprotective titer (HAI titer ≥ 1:160) recommended for IIV evaluation in children, we found that among subjects who were seropositive at baseline, 69% achieved seroprotection for both A/H1N1 and A/H3N2, while among those who were seronegative at baseline, seroprotection was achieved in 11% for A/H1N1 and 22% for A/H3N2. The IPV group had high baseline polio antibody seropositivity and appropriate responses to vaccination. Our data emphasize the importance of a two-dose IIV3 series in vaccine naïve children. IIV and IPV vaccines were immunogenic in Senegalese children.

Effects of Sequential Influenza A(H1N1)pdm09 Vaccination on Antibody Waning

BACKGROUND

Antibody waning following influenza vaccination has been repeatedly evaluated, but waning has rarely been studied in the context of longitudinal vaccination history.

METHODS

We developed a Bayesian hierarchical model to assess the effects of sequential influenza A(H1N1)pdm09 vaccination on hemagglutination inhibition antibody boosting and waning in a longitudinal cohort of older children and adults from 2011 to 2016, a period during which the A(H1N1)pdm09 vaccine strain did not change.

RESULTS

Antibody measurements from 2057 serum specimens longitudinally collected from 388 individuals were included. Average postvaccination antibody titers were similar across successive vaccinations, but the rate of antibody waning increased with each vaccination. The antibody half-life was estimated to decrease from 32 months (95% credible interval [CrI], 22-61 months) following first vaccination to 9 months (95% CrI, 7-15 months) following a seventh vaccination.

CONCLUSIONS

Although the rate of antibody waning increased with successive vaccination, the estimated antibody half-life was longer than a typical influenza season even among the most highly vaccinated. This supports current recommendations for vaccination at the earliest opportunity. Patterns of boosting and waning might be different with the influenza A(H3N2) subtype, which evolves more rapidly and has been most associated with reduced effectiveness following repeat vaccination.

Does self-rated health status influence receipt of an annual flu vaccination?

Despite 79,400 deaths due to the influenza (flu) virus during the 2017-18 season, <50% of US adults receive an annual flu vaccination (AFV). Self-rated health status (SRH) is associated with health behavior utilization. The current study aims to determine if an association exists between an individual's SRH and their receipt of an AFV. In the 2017 US Behavioral Risk Factor Surveillance System survey, 39.1% of respondents had received a flu vaccination within the last 12 months. There was a statistically significant difference (p < 0.0001) between the vaccination rates of men (35.7%) and women (42.4%). There was a significant positive association between SRH and AFV for individuals who self-reported an SRH of either "Fair" (AOR 1.19; 95% CI 1.12-1.27) or "Poor" (AOR 1.24; 95% CI 1.14-1.35), compared to those reporting a status of "Excellent". For those reporting an SRH status of "Fair", there was a significant positive association for both men (AOR 1.20; 95% CI 1.10-1.32) and women (AOR 1.17; 95% CI 1.08-1.28). An association was also found for men (AOR 1.203; 95% CI 1.09-1.39) and women (AOR 1.23; 95% CI 1.09-1.399) who reported their SRH as "Poor". Only women showed a significant association (AOR 1.12; 95% CI 1.04-1.20) among those whose SRH was "Good". No association was found for individuals who reported SRH as "Very Good". These findings are of interest to health policy makers as they show there is still work required to convince individuals with a high SRH that they too need to receive an AFV.

Measuring influenza hemagglutinin (HA) stem-specific antibody-dependent cellular cytotoxicity (ADCC) in human sera using novel stabilized stem nanoparticle probes

BACKGROUND

Generating vaccine that confers a complete protection is a major goal in designing a universal influenza vaccine. Currently, there is a considerable interest in the broadly neutralizing antibodies (bnAb) targeting the conserved HA stem region. These antibodies have been shown to activate cellular immune responses, such as ADCC, in addition to their neutralization activity. We had previously demonstrated that immunization with H1-based stabilized stem (SS) nanoparticles (np) protects against heterosubtypic lethal H5N1 challenge, despite the absence of detectable neutralizing activity. Utilizing these novel SS probes to develop an ADCC assay would help in understanding the mechanism of action of stem-specific antibodies, as well as evaluating future influenza vaccines.

OBJECTIVES

To develop a new protocol to assess the ADCC activity mediated by stem-directed antibodies in human sera using novel SS np probes.

STUDY DESIGN

Human sera samples were screened for binding and ADCC activities to different influenza group 1 SS probes (H1, H2, and H5) using trimeric SS or multivalent SS-np (n = 8 trimers) formats.

RESULTS

Initial screening revealed 63% (57/90) seroprevalence of anti-HA (H1) stem-epitope antibodies, as determined by the differential binding to HA SS and its corresponding epitope-mutant (Ile45Arg/Thr49Arg) probe. Using equimolar amounts, the multivalent presentation of HA SS on np induced significantly higher ADCC activity compared to the monovalent (trimer) SS probes (2-6 fold increase). Further, ADCC activity was similarly reported against different group 1 influenza subtypes: H1, H2, and H5. Importantly, ADCC was mediated mainly by antibodies targeting the bnAb-epitope on the HA stem.

CONCLUSION

We report on an assay to measure stem-specific ADCC activity using SS np probes. Our results indicate high prevalence of HA-stem antibodies with cross-reactive ADCC activity. Such assay could be utilized in the assessment of next generation influenza vaccines.

Effects of Influenza Vaccination in the United States During the 2017-2018 Influenza Season

BACKGROUND

The severity of the 2017-2018 influenza season in the United States was high, with influenza A(H3N2) viruses predominating. Here, we report influenza vaccine effectiveness (VE) and estimate the number of vaccine-prevented influenza-associated illnesses, medical visits, hospitalizations, and deaths for the 2017-2018 influenza season.

METHODS

We used national age-specific estimates of 2017-2018 influenza vaccine coverage and disease burden. We estimated VE against medically attended reverse-transcription polymerase chain reaction-confirmed influenza virus infection in the ambulatory setting using a test-negative design. We used a compartmental model to estimate numbers of influenza-associated outcomes prevented by vaccination.

RESULTS

The VE against outpatient, medically attended, laboratory-confirmed influenza was 38% (95% confidence interval [CI], 31%-43%), including 22% (95% CI, 12%-31%) against influenza A(H3N2), 62% (95% CI, 50%-71%) against influenza A(H1N1)pdm09, and 50% (95% CI, 41%-57%) against influenza B. We estimated that influenza vaccination prevented 7.1 million (95% CrI, 5.4 million-9.3 million) illnesses, 3.7 million (95% CrI, 2.8 million-4.9 million) medical visits, 109 000 (95% CrI, 39 000-231 000) hospitalizations, and 8000 (95% credible interval [CrI], 1100-21 000) deaths. Vaccination prevented 10% of expected hospitalizations overall and 41% among young children (6 months-4 years).

CONCLUSIONS

Despite 38% VE, influenza vaccination reduced a substantial burden of influenza-associated illness, medical visits, hospitalizations, and deaths in the United States during the 2017-2018 season. Our results demonstrate the benefit of current influenza vaccination and the need for improved vaccines.

The association between history of screening for cancer and receipt of an annual flu vaccination: Are there reinforcing effects of prevention seeking?

BACKGROUND

Receipt of an annual flu vaccination (AFV) is a preventative health measure that reduces the risk of infection with the flu. Screening for cancer (SC) is another recommended preventative health measure. The current study hypothesizes that people who have previously obtained a cancer screening are motivated to receive other preventative health measures.

METHODS

Testing the association between a history of SC and receipt of an AFV used data from the 2016 Behavioral Risk Factor Surveillance System survey. The association was investigated using weighted and adjusted multivariable logistic regression models on multiple age-based groups chosen according to cancer screening recommendations.

RESULTS

The odds of individuals with a history of SC receiving an AFV were significantly greater in women screened for colorectal cancer, breast cancer, and colorectal cancer, and men screened for colorectal cancer, when compared with those without a history of SC after adjusting for confounders of interest. It is notable that no association was found between screening for cervical cancer and the receipt of AFV for women aged 30-65 years (odds ratio: 1.06; 95% confidence interval: 0.92, 1.21), and 50-65 years (odds ratio: 1.14; 95% confidence interval: 0.93, 1.40).

CONCLUSIONS

More research is necessary to understand why cervical cancer screenings are not associated with receipt of an AFV.

Does health plan type influence receipt of an annual influenza vaccination?

BACKGROUND

The influenza virus caused 48.8 million people to fall ill and 79 400 deaths during the 2017-2018 influenza season, yet less than 50% of US adults receive an annual flu vaccination (AFV). Having health insurance coverage influences whether individuals receive an AFV. The current study aims to determine if an association exists between an individual's health plan type (HPT) and their receipt of an AFV.

METHODS

Data from the 2017 Behavioral Risk Factor Surveillance System and the optional 'Health Care Access' module were used for this study. The final study sample size was 35 684. Multivariable weighted and adjusted logistic regression models were conducted to investigate the association between HPT and AFV.

RESULTS

Medicare coverage was significantly associated with an increase in AFV for both men (adjusted OR (AOR) 1.62 (95% CI 1.28 to 2.06)) and women (AOR 1.28 (95% CI 1.00 to 1.53)). For men, other sources of coverage were also significantly positively associated with AFV (AOR 1.67 (95% CI 1.27 to 2.19)), while for women obtaining coverage on their own was significantly negatively associated with AFV (AOR 0.75 (95% CI 0.59 to 0.97)).

CONCLUSION

These findings are of interest to health policy makers as these show there are HPTs which are effective at improving vaccination rates. Adopting methods used by these HPTs could help the USA reach its Healthy People 2020 AFV coverage goal of 70%.

Novel calixarene-based surfactant enables low dose split inactivated vaccine protection against influenza infection

Influenza A viruses cause major morbidity and represent a severe global health problem. Current influenza vaccines are mainly egg-based products requiring the split of whole viruses using classical detergents such as Triton X-100, which implies certain limitations. Here, we report the use of the novel calixarene-based surfactant CALX133ACE as an alternative to classical detergents for influenza inactivated split vaccine preparation. We confirmed that CALX133ACE-based split HA antigens are fully functional and quantifiable by the "gold standard" method SRID. Additionally, as in the case of the Triton X-100-based split, the CALX133ACE-based split antigens are stable for at least 6 months at 4 °C. Moreover, immunization of mice with CALX133ACE-based split NYMC X-179A (H1N1) antigens harboring 10 to 30-fold less antigen than the commercialized trivalent inactivated vaccines Vaxigrip® or Fluviral® induced comparable efficient protection and neutralizing antibody responses against A(H1N1)pdm09 infection. Taken together, our results demonstrate for the first time the use of a calixarene-based detergent as an efficient splitting agent for the production of optimized influenza split antigens, paving the way for significant improvement in the vaccine manufacturing process, notably with regard to the current regulation on the prohibition of endocrine disruptors, such as Triton X-100.

Hypoplastic Left Heart Syndrome: An Overview for Primary Care Providers

Hypoplastic left heart syndrome is one of the most complex congenital heart diseases and requires several cardiac surgeries for survival. The diagnosis is usually established prenatally or shortly after birth. Each stage of surgery poses a unique hemodynamic situation that requires deeper understanding to manage common pediatric problems such as dehydration and respiratory infections. Careful multidisciplinary involvement in the care of these complex patients is improving their outcome; however, morbidity and mortality are still substantial. In this review, we focus on the hemodynamic aspects of various surgical stages that a primary care provider should know to manage these challenging patients.

SIMON, an Automated Machine Learning System, Reveals Immune Signatures of Influenza Vaccine Responses

Machine learning holds considerable promise for understanding complex biological processes such as vaccine responses. Capturing interindividual variability is essential to increase the statistical power necessary for building more accurate predictive models. However, available approaches have difficulty coping with incomplete datasets which is often the case when combining studies. Additionally, there are hundreds of algorithms available and no simple way to find the optimal one. In this study, we developed Sequential Iterative Modeling "OverNight" (SIMON), an automated machine learning system that compares results from 128 different algorithms and is particularly suitable for datasets containing many missing values. We applied SIMON to data from five clinical studies of seasonal influenza vaccination. The results reveal previously unrecognized CD4⁺ and CD8⁺ T cell subsets strongly associated with a robust Ab response to influenza Ags. These results demonstrate that SIMON can greatly speed up the choice of analysis modalities. Hence, it is a highly useful approach for data-driven hypothesis generation from disparate clinical datasets. Our strategy could be used to gain biological insight from ever-expanding heterogeneous datasets that are publicly available.

Influenza vaccine strategies for solid organ transplant recipients

PURPOSE OF REVIEW

The aim of this study was to highlight recent evidence on important aspects of influenza vaccination in solid organ transplant recipients.

RECENT FINDINGS

Influenza vaccine is the most evaluated vaccine in transplant recipients. The immunogenicity of the vaccine is suboptimal after transplantation. Newer formulations such as inactivated unadjuvanted high-dose influenza vaccine and the administration of a booster dose within the same season have shown to increase response rates. Intradermal vaccination and adjuvanted vaccines did not show clear benefit over standard influenza vaccines. Recent studies in transplant recipients do not suggest a higher risk for allograft rejection, neither after vaccination with a standard influenza vaccine nor after the administration of nonstandard formulation (high-dose, adjuvanted vaccines), routes (intradermally) or a booster dose. Nevertheless, influenza vaccine coverage in transplant recipients is still unsatisfactory low, potentially due to misinterpretation of risks and benefits.

SUMMARY

Annual influenza vaccination is well tolerated and is an important part of long-term care of solid organ transplant recipients.

Knowledge, attitudes and practices related to influenza illness and vaccination in children: Role of awareness campaigns in changing parents' attitudes toward influenza vaccination in Jordan

BACKGROUND

Influenza infection is associated with a significant health burden in children, especially in developing countries. The influenza vaccine is an important preventive strategy for flu illness. Aim of this study to assess knowledge, attitudes and practices (KAP) related to influenza illness and vaccination in children in the Jordanian population and to study the effect of awareness campaigns on changing the attitudes of parents toward vaccinating their children against influenza.

METHODS

A cross-sectional study was conducted among families visiting shopping malls and parks in November 2016. A questionnaire was administered via in-person interviews. Answers to KAP questions regarding influenza illness and vaccination were summed, with a total KAP score of 30. Facts about influenza illness and vaccination were explained to parents and provided in printed pamphlets.

RESULTS

There were 1241 respondents. 10.9% of participants had vaccinated their children during the last season 2015/2016. The mean KAP score (standard deviation) was 16.21 (4.61). People living in urban areas, with high monthly income >600 JD and healthcare workers had higher KAP scores than their counterparts. Compared to other sources of information about the influenza vaccine, health resources correlated most with vaccinating children. Awareness and educational pamphlets changed attitudes positively in 29% of parents who refused the influenza vaccine for their children.

CONCLUSIONS

Awareness about influenza illness and vaccination is insufficient, and the coverage rate of influenza vaccination in children is low in the Jordanian population. Implementing public health policies is necessary to spread knowledge about influenza illness and vaccination and to promote the practice of receiving the influenza vaccine in children. Educational campaigns are helpful in changing the attitudes of parents toward vaccinating their children against the flu.

Altered antigenicity and immunogenicity of human papillomavirus virus-like particles in the presence of thimerosal

Thimerosal has been widely used as a preservative in human vaccines for decades. Thimerosal, a thiol capping agent with ethyl mercury being the active degradant, could have impacts on the vaccine potency due to potential thiol modification. The effects on the antigenicity and immunogenicity of human papillomavirus (HPV) virus-like particles (VLPs) in the presence of thimerosal was studied. In general, reduced binding activity was observed between HPV antigens and monoclonal antibodies (mAbs) upon thimerosal treatment, accompanied by reduced protein conformational stability. The immunogenicity of a pentavalent vaccine formulation (HPV6, HPV11, HPV16, HPV18 and hepatitis E virus) with or without thimerosal was studied in mice. The functional antibody titres, as well as the binding titres, were determined, showing a substantial decrease for vaccine formulations containing thimerosal for HPV16/18. Similarly, epitope-specific competition assays using specific and functional mAbs as tracers also showed a significant reduction in immunogenicity for HPV16/18 in the presence of thimerosal. Structural alterations in the capsid protein for HPV18 were observed with cryo-electron microscopy and 3-dimensional reconstruction in the comparative structural analysis. The results should alert scientists in formulation development field on the choice for vaccine preservatives, in particular for thiol-containing antigens.

Text Message Reminders for Child Influenza Vaccination in the Setting of School-Located Influenza Vaccination: A Randomized Clinical Trial

Half of US school children receive influenza vaccine. In our previous trials, school-located influenza vaccination (SLIV) raised vaccination rates by 5 to 8 percentage points. We assessed whether text message reminders to parents could raise vaccination rates above those observed with SLIV. Within urban elementary schools we randomized families into text message + SLIV (intervention) versus SLIV alone (comparison). All parents were sent 2 backpack notifications plus 2 autodialer phone reminders about SLIV at a single SLIV clinic. Intervention group parents also were sent 3 text messages from the school nurse encouraging flu vaccination via either primary care or SLIV. Among 15 768 children at 32 schools, vaccination rates were text + SLIV (40%) and SLIV control (40%); 4% of students per group received influenza vaccination at SLIV. Text message reminders did not raise influenza vaccination rates above those observed with SLIV alone. More intensive interventions are needed to raise influenza vaccination rates.

Improving influenza vaccination uptake among healthcare workers by on-site influenza vaccination campaign in a tertiary children hospital

Children are at higher risk of influenza complications. The goals of this article are, estimating influenza vaccination coverage of Health Care Workers (HCWs) in tertiary children hospital, evaluating attitudes and practices of HCWs and evaluating whether HCWs vaccination uptake improved with onsite vaccination campaign. This was a before-after trial, which was carried out in a tertiary children hospital at 2017-2018 influenza season. The vaccination team visited all participants and collected information about previous vaccination uptake, attitudes and beliefs of HCWs by means of an anonymous questionnaire. Moreover, the influenza vaccine was offered onsite to all participants. A total of 572 HCWs participated in this study (response rate: 94.2%). Coverage was 10.8% in 2016-17 season and 39.9% in 2017-18 season (p < 0.0001). Multivariate regression analysis showed that being younger than 35 years (OR: 2.09), being vaccinated in previous season (OR: 47.02) and professional category of the participant (clinicians being reference group; OR: 1.73 for support staff and OR: 0.23 for nurses,) were significantly associated with vaccination uptake in 2017-18 season [95% CI]. None of the participants with former bad experience about vaccination was vaccinated in 2017-2018 season. And 90% of the participants having lack of knowledge about the vaccine were vaccinated in 2017-2018 season. After onsite vaccination campaign, influenza vaccination coverage improved significantly among HCWs. In order to achieve target vaccination coverage we should break down the prejudices with a comprehensive education program. Abbreviations: OR- Odds ratio; CI- confidence interval.

Caregiver's attitudes, beliefs, and experiences for influenza vaccination in Australian children with medical comorbidities

BACKGROUND

Influenza vaccination is recommended and funded for Australian children with medical comorbidities that increase their risk of severe influenza. Despite this, influenza vaccine coverage remains low within this population. We examined caregivers' attitudes and practices for influenza vaccination in children with medical comorbidities.

METHODS

Cross-sectional surveys were conducted with caregivers of children (6 months to <18 years old) with medical comorbidities attending sub-speciality paediatric outpatient clinics at the Royal Children's Hospital (Melbourne), Princess Margaret Hospital (Perth), and Leading Steps private paediatric clinic (Gold Coast). Multivariate linear regression was used to identify surveys responses predictive of receipt of influenza vaccination in 2017.

RESULTS

From the 611 surveys collected, 556 were suitable for analysis. Caregiver reported 2017 influenza vaccine coverage was 52.2% in children with medical comorbidities. Caregivers who believed influenza vaccines to be ≥50% effective were more likely to vaccinate their children (adjusted Odds Ratio [aOR]:3.79 (2.41; 5.96). Those who expressed concerns about vaccine side effects were less likely to vaccinate their children (aOR: 0.49 [95% CI: 0.30; 0.80]). Influenza vaccine uptake was significantly more likely for children who had been previously recommended influenza vaccination by their hospital-based physician (aOR: 4.33 [95% CI: 2.58; 7.27]) and had previously received a hospital-based vaccination (aOR: 3.11 [95% CI 1.79; 5.40]). Hospital-based physicians were also caregivers' most commonly reported source of trusted vaccination information (63.5%). Whilst only 29.3% of caregivers reported their child had been recommended influenza vaccination during a previous admission, 80.1% of caregivers stated they were receptive to their child receiving potential future influenza vaccinations during hospitalisations.

CONCLUSIONS

Reported influenza vaccination coverage in children with medical comorbidities remains inadequate. An important finding of this study is that influenza vaccination recommendation by children's hospital physicians and previous vaccine receipt in hospital was associated with vaccine uptake. Opportunities for vaccination, especially during hospitalisation, must be examined.

Evaluation of correlates of protection against influenza A(H3N2) and A(H1N1)pdm09 infection: Applications to the hospitalized patient population

BACKGROUND

Influenza vaccines are important for prevention of influenza-associated hospitalization. However, the effectiveness of influenza vaccines can vary by year and influenza type and subtype and mechanisms underlying this variation are incompletely understood. Assessments of serologic correlates of protection can support interpretation of influenza vaccine effectiveness in hospitalized populations.

METHODS

We enrolled adults hospitalized for treatment of acute respiratory illnesses during the 2014-2015 and 2015-2016 influenza seasons whose symptoms began <10 days prior to enrollment. Influenza infection status was determined by RT-PCR. Influenza vaccination status was defined by self-report and medical record/registry documentation. Serum specimens collected at hospital admission were tested in hemagglutination-inhibition (HAI) and neuraminidase-inhibition (NAI) assays. We evaluated how well antibody measured in these specimens represented pre-infection immune status, and measured associations between antibody and influenza vaccination and infection.

RESULTS

Serum specimens were retrieved for 315 participants enrolled during the 2014-2015 season and 339 participants during the 2015-2016 season. Specimens were collected within 3 days of illness onset from 65% of participants. Geometric mean titers (GMTs) did not vary by the number of days from illness onset to specimen collection among influenza positive participants suggesting that measured antibody was representative of pre-infection immune status rather than a de novo response to infection. In both seasons, vaccinated participants had higher HAI and NAI GMTs than unvaccinated. HAI titers against the 2014-2015 A(H3N2) vaccine strain did not correlate with protection from infection with antigenically-drifted A(H3N2) viruses that circulated that season. In contrast, higher HAI titers against the A(H1N1)pdm09 vaccine strain were associated with reduced odds of A(H1N1)pdm09 infection in 2015-2016.

CONCLUSIONS

Serum collected shortly after illness onset at hospital admission can be used to assess correlates of protection against influenza infection. Broader implementation of similar studies would provide an opportunity to understand the successes and shortcomings of current influenza vaccines.

The effectiveness of influenza vaccination in preventing hospitalizations in elderly in Beijing, 2016-18

BACKGROUND

Influenza vaccinations play an important role in preventing influenza related hospitalizations. The objective of this study was to estimate the effectiveness of vaccination in protecting Beijing residents aged ≥60 years from influenza related hospitalizations during the 2016/17 and 2017/18 influenza seasons.

METHODS

Patients who met the definition of severe acute respiratory infection (SARI) and were hospitalized in the nine sentinel hospitals in Beijing during the 2016/17 and 2017/18 influenza seasons were identified as the study population. The vaccination status of patients was obtained from a vaccination registry. Real-time reversetranscription polymerasechainreaction (RT-PCR) experiments were conducted to test pharyngeal or lower respiratory tract samples collected from SARI patients for influenza A and B viruses. Vaccine effectiveness (VE) was examined using a test-negative design that compare the odds of vaccination among influenza positives and negatives, adjusting for calendar week of illness onset, age, and underlying medical conditions.

RESULTS

We identified 50,364 patients in the study, in which there were 145 influenza cases and 528 influenza-negative controls aged ≥60 years in 2016/17 season and 149 cases and 358 controls aged ≥60 years in 2017/18 season. The most commonly identified subtype among participants was influenza A(H3N2) in 2016/17 and 2017/18 season (78.5% and 70.6%). Among the adults aged ≥60 years, the adjusted VE of vaccination against any influenza virus for serious acute respiratory infection (SARI) patients was 32.8% (95% confidence interval [CI]: -22.0 to 63.0%) in 2016/17 season. While the adjusted VE in 2017/18 season were 4.6% (95% CI: -72.4 to 47.2%) against any types of influenza, 29.2% (95% CI: -92.9 to 74%) against influenza A(H1N1)pdm09, -37.7% (95% CI: -293.8; 51.9%) against influenza A(H3N2) viruses, and 3.6% (95% CI: -113.8 to 56.5%) against influenza B.

CONCLUSION

The influenza vaccine provided moderate protection in 2016/17 season and mild protection in 2017/18 season for influenza related inpatients of adults aged ≥60 years in Beijing.

Novel Approaches for The Development of Live Attenuated Influenza Vaccines

Influenza virus still represents a considerable threat to global public health, despite the advances in the development and wide use of influenza vaccines. Vaccination with traditional inactivate influenza vaccines (IIV) or live-attenuated influenza vaccines (LAIV) remains the main strategy in the control of annual seasonal epidemics, but it does not offer protection against new influenza viruses with pandemic potential, those that have shifted. Moreover, the continual antigenic drift of seasonal circulating influenza viruses, causing an antigenic mismatch that requires yearly reformulation of seasonal influenza vaccines, seriously compromises vaccine efficacy. Therefore, the quick optimization of vaccine production for seasonal influenza and the development of new vaccine approaches for pandemic viruses is still a challenge for the prevention of influenza infections. Moreover, recent reports have questioned the effectiveness of the current LAIV because of limited protection, mainly against the influenza A virus (IAV) component of the vaccine. Although the reasons for the poor protection efficacy of the LAIV have not yet been elucidated, researchers are encouraged to develop new vaccination approaches that overcome the limitations that are associated with the current LAIV. The discovery and implementation of plasmid-based reverse genetics has been a key advance in the rapid generation of recombinant attenuated influenza viruses that can be used for the development of new and most effective LAIV. In this review, we provide an update regarding the progress that has been made during the last five years in the development of new LAIV and the innovative ways that are being explored as alternatives to the currently licensed LAIV. The safety, immunogenicity, and protection efficacy profile of these new LAIVs reveal their possible implementation in combating influenza infections. However, efforts by vaccine companies and government agencies will be needed for controlled testing and approving, respectively, these new vaccine methodologies for the control of influenza infections.

Burden, effectiveness and safety of influenza vaccines in elderly, paediatric and pregnant populations

Vaccination is the most practical means available for preventing influenza. Influenza vaccines require frequent updates to keep pace with antigenic drift of the virus, and the effectiveness, and sometimes the safety, of the vaccine can therefore vary from season to season. Three key populations that the World Health Organization recommends should be prioritized for influenza vaccination are pregnant women, children younger than 5 years of age and the elderly. This review discusses the burden of influenza and the safety and effectiveness profile of influenza vaccines recommended for these groups.

Can online self-reports assist in real-time identification of influenza vaccination uptake? A cross-sectional study of influenza vaccine-related tweets in the USA, 2013-2017

INTRODUCTION

The Centers for Disease Control and Prevention (CDC) spend significant time and resources to track influenza vaccination coverage each influenza season using national surveys. Emerging data from social media provide an alternative solution to surveillance at both national and local levels of influenza vaccination coverage in near real time.

OBJECTIVES

This study aimed to characterise and analyse the vaccinated population from temporal, demographical and geographical perspectives using automatic classification of vaccination-related Twitter data.

METHODS

In this cross-sectional study, we continuously collected tweets containing both influenza-related terms and vaccine-related terms covering four consecutive influenza seasons from 2013 to 2017. We created a machine learning classifier to identify relevant tweets, then evaluated the approach by comparing to data from the CDC's FluVaxView. We limited our analysis to tweets geolocated within the USA.

RESULTS

We assessed 1 124 839 tweets. We found strong correlations of 0.799 between monthly Twitter estimates and CDC, with correlations as high as 0.950 in individual influenza seasons. We also found that our approach obtained geographical correlations of 0.387 at the US state level and 0.467 at the regional level. Finally, we found a higher level of influenza vaccine tweets among female users than male users, also consistent with the results of CDC surveys on vaccine uptake.

CONCLUSION

Significant correlations between Twitter data and CDC data show the potential of using social media for vaccination surveillance. Temporal variability is captured better than geographical and demographical variability. We discuss potential paths forward for leveraging this approach.

Increased Risk of Influenza and Influenza-Related Complications Among 140,480 Patients With Inflammatory Bowel Disease

BACKGROUND

Diseases of immune dysregulation are associated with an increased risk of viral infections, some of which may be preventable. To date, there are very limited data on the incidence and risk of influenza and related complications in patients with inflammatory bowel disease (IBD). Furthermore, the impact of immunosuppressive medications on that risk is unclear. Therefore, the aim of this study was to estimate the incidence and severity of influenza infections in IBD patients. In addition, we looked specifically at the effect of medications on influenza risk.

METHODS

Using the MarketScan Database (January 2008 to December 2011), we conducted a retrospective cohort study to estimate the incidence of influenza and risk of related complications in IBD patients compared with those without IBD. We employed a nested case-control study design to evaluate the potential independent effect of IBD medications on influenza risk.

RESULTS

A total of 140,480 patients with IBD and non-IBD controls were studied. There were 2963 patients with influenza compared with 1941 non-IBD subjects. Inflammatory bowel disease patients had an increased influenza risk compared with those without IBD (incidence rate ratio, 1.54; 95% confidence interval [CI], 1.49-1.63). A higher rate of hospitalizations (162/2994 [5.4%] vs 36/1941 [1.85%]; P < 0.001) was noted. Systemic corticosteroids were found to be independently associated with influenza (odds ratio, 1.22; 95% CI, 1.08-1.38).

CONCLUSIONS

Inflammatory bowel disease patients had an increased risk of influenza compared with those without IBD and were more likely to require hospitalization. Steroids were the only medication class independently associated with flu risk.

A newly developed tetraplex real-time RT-PCR for simultaneous screening of influenza virus types A, B, C and D

BACKGROUND

Human- or avian-to-swine transmissions have founded several autonomously circulating influenza A virus (IAV) lineages in swine populations that cause economically important respiratory disease. Little is known on other human influenza virus types, like B (IBV) and C (ICV) in European swine, and of the recently detected novel animal influenza virus type D (IDV).

OBJECTIVES

Development of a cost-effective diagnostic tool for large-scale surveillance programmes targeting all four influenza virus types.

METHODS

An influenza ABCD tetraplex real-time RT-PCR (RT-qPCR) was developed in the frame of this study. A selection of reference virus strains and more than 4000 porcine samples from a passive IAV surveillance programme in European swine with acute respiratory disease were examined.

RESULTS

Two IBV, a single IDV but no ICV infections were identified by tetraplex RT-qPCR. IBV and IDV results were confirmed by conventional RT-PCR and partial sequence analysis.

CONCLUSIONS

The tetraplex RT-qPCR proved fit for purpose as a sensitive, specific and high-throughput tool to study influenza virus transmission at the human-animal interface. Complementing close-meshed active virological and serological surveillance is required to better understand the true incidence and prevalence of influenza virus type B, C and D infections in swine.

Modulation of Innate Immune Responses by the Influenza A NS1 and PA-X Proteins

Influenza A viruses (IAV) can infect a broad range of animal hosts, including humans. In humans, IAV causes seasonal annual epidemics and occasional pandemics, representing a serious public health and economic problem, which is most effectively prevented through vaccination. The defense mechanisms that the host innate immune system provides restrict IAV replication and infection. Consequently, to successfully replicate in interferon (IFN)-competent systems, IAV has to counteract host antiviral activities, mainly the production of IFN and the activities of IFN-induced host proteins that inhibit virus replication. The IAV multifunctional proteins PA-X and NS1 are virulence factors that modulate the innate immune response and virus pathogenicity. Notably, these two viral proteins have synergistic effects in the inhibition of host protein synthesis in infected cells, although using different mechanisms of action. Moreover, the control of innate immune responses by the IAV NS1 and PA-X proteins is subject to a balance that can determine virus pathogenesis and fitness, and recent evidence shows co-evolution of these proteins in seasonal viruses, indicating that they should be monitored for enhanced virulence. Importantly, inhibition of host gene expression by the influenza NS1 and/or PA-X proteins could be explored to develop improved live-attenuated influenza vaccines (LAIV) by modulating the ability of the virus to counteract antiviral host responses. Likewise, both viral proteins represent a reasonable target for the development of new antivirals for the control of IAV infections. In this review, we summarize the role of IAV NS1 and PA-X in controlling the antiviral response during viral infection.

Temperature Sensitive Mutations in Influenza A Viral Ribonucleoprotein Complex Responsible for the Attenuation of the Live Attenuated Influenza Vaccine

Live attenuated influenza vaccines (LAIV) have prevented morbidity and mortality associated with influenza viral infections for many years and represent the best therapeutic option to protect against influenza viral infections in humans. However, the development of LAIV has traditionally relied on empirical methods, such as the adaptation of viruses to replicate at low temperatures. These approaches require an extensive investment of time and resources before identifying potential vaccine candidates that can be safely implemented as LAIV to protect humans. In addition, the mechanism of attenuation of these vaccines is poorly understood in some cases. Importantly, LAIV are more efficacious than inactivated vaccines because their ability to mount efficient innate and adaptive humoral and cellular immune responses. Therefore, the design of potential LAIV based on known properties of viral proteins appears to be a highly appropriate option for the treatment of influenza viral infections. For that, the viral RNA synthesis machinery has been a research focus to identify key amino acid substitutions that can lead to viral attenuation and their use in safe, immunogenic, and protective LAIV. In this review, we discuss the potential to manipulate the influenza viral RNA-dependent RNA polymerase (RdRp) complex to generate attenuated forms of the virus that can be used as LAIV for the treatment of influenza viral infections, one of the current and most effective prophylactic options for the control of influenza in humans.

Low coverage rate and awareness of influenza vaccine among older people in Shanghai, China: A cross-sectional study

Background: Older individuals are at high risk for morbidity and mortality due to influenza, and the most effective way to prevent influenza is yearly vaccination. In China, the influenza vaccine is not covered by the national Expanded Program on Immunization, and more evidence is needed about influenza vaccine usage among older individuals.

Objective: To determine the influenza vaccination coverage and its influencing factors, and understand barriers to older adults receiving influenza vaccinations in Shanghai, China.

Methods: A cross-sectional survey was conducted with residents aged 60 and older. Vaccination status in the 2016–17 influenza season and reasons for or against vaccination were surveyed. The vaccination coverage rates were adjusted by gender, age and community distribution, and potential factors influencing vaccination uptake were determined by bivariate logistic regression.

Results: In total, 253 of the 4417 respondents received an influenza vaccine during the 2016–17 season, yielding an adjusted coverage rate of 5.2% (95% CI, 4.5-5.8). The frequency of receiving the vaccine was higher for older individuals living with family/friends than that for those living alone (p < 0.05), and lower among individuals with chronic respiratory diseases (p < 0.05). Among unvaccinated respondents, lack of influenza vaccine awareness was the most common reason for being unvaccinated (48.3%, 2012/4164).

Conclusion: Influenza vaccination coverage is extremely low among older people in Shanghai, and lack of awareness of the influenza vaccine might be a potential barrier to vaccination. Our study highlights the need for an appropriate influenza vaccination strategy and program targeting the older population.

Altered immune cell follicular dynamics in HIV infection following influenza vaccination

HIV infection changes the lymph node (LN) tissue architecture, potentially impairing the immunologic response to antigenic challenge. The tissue-resident immune cell dynamics in virologically suppressed HIV+ patients on combination antiretroviral therapy (cART) are not clear. We obtained LN biopsies before and 10 to 14 days after trivalent seasonal influenza immunization from healthy controls (HCs) and HIV+ volunteers on cART to investigate CD4+ T follicular helper (Tfh) and B cell dynamics by flow cytometry and quantitative imaging analysis. Prior to vaccination, compared with those in HCs, HIV+ LNs exhibited an altered follicular architecture, but harbored higher numbers of Tfh cells and increased IgG+ follicular memory B cells. Moreover, Tfh cell numbers were dependent upon preservation of the follicular dendritic cell (FDC) network and were predictive of the magnitude of the vaccine-induced IgG responses. Interestingly, postvaccination LN samples in HIV+ participants had significantly (P = 0.0179) reduced Tfh cell numbers compared with prevaccination samples, without evidence for peripheral Tfh (pTfh) cell reduction. We conclude that influenza vaccination alters the cellularity of draining LNs of HIV+ persons in conjunction with development of antigen-specific humoral responses. The underlying mechanism of Tfh cell decline warrants further investigation, as it could bear implications for the rational design of HIV vaccines.

Seasonal Influenza Vaccine Acceptance among Pregnant Women in Zhejiang Province, China: Evidence Based on Health Belief Model

Background: Reasons for acceptance of seasonal influenza vaccine (SIV) vaccination among pregnant women in China are poorly understood. We assessed the intention to accept SIV among pregnant women in Zhejiang province, by using a self-administrated structured questionnaire developed on the basis of health belief model (HBM). Methods: From 1 January to 31 March 2014, pregnant women with ≥12 gestational weeks who attended antenatal clinics (ANCs) at public hospitals in 6 out of 90 districts were surveyed using a self-administered questionnaire that covered knowledge, attitudes, and beliefs related to SIV vaccination and influenza infection. We examined the associations between the acceptance of SIV vaccination and the demographic factors and HBM constructs using the logistic regression model, calculating the adjusted odds ratio (AOR). Results: Of the 1252 participants, 76.28% were willing to receive the SIV vaccination during their current pregnancy. High levels of perceived susceptibility of influenza (AOR = 1.75 (95%CI: 1.36–2.08)), high levels of perceived severity of influenza (AOR = 1.62 (95%CI: 1.25–1.95)), high level of perceived benefits of vaccination (AOR = 1.97 (95%CI: 1.76–2.21)), and high levels of cues to action were positively associated with the acceptance of SIV vaccination among pregnant women (AOR = 2.03 (95%CI: 1.70–2.69)), while high level of perceived barriers of vaccination was a negative determinant (AOR = 0.76 (95%CI: 0.62–0.94)). Conclusions: Poor knowledge and negative attitude towards SIV were associated with the poor acceptance of SIV. Health providers’ recommendations were important to pregnant women’s acceptance of SIV. Health education and direct communication strategies on SIV vaccination and influenza infection are necessary to improve the acceptance of SIV vaccination among pregnant women.