Influenzavirus infections in Seattle families, 1975-1979. I. Study design, methods and the occurrence of infections by time and age

Block the Spread: Barriers to Transmission of Influenza Viruses

Respiratory viruses, such as influenza viruses, cause significant morbidity and mortality worldwide through seasonal epidemics and sporadic pandemics. Influenza viruses transmit through multiple modes including contact (either direct or through a contaminated surface) and inhalation of expelled aerosols. Successful human to human transmission requires an infected donor who expels virus into the environment, a susceptible recipient, and persistence of the expelled virus within the environment. The relative efficiency of each mode can be altered by viral features, environmental parameters, donor and recipient host characteristics, and viral persistence. Interventions to mitigate transmission of influenza viruses can target any of these factors. In this review, we discuss many aspects of influenza virus transmission, including the systems to study it, as well as the impact of natural barriers and various nonpharmaceutical and pharmaceutical interventions.

High attack rate of COVID-19 in an organized tour group of vaccinated travellers to Iceland

In a COVID-19 outbreak in a group of 25 twice-vaccinated Israeli travellers, the attack rate was 84%, despite negative preflight polymerase chain reaction tests. This extremely high breakthrough infection rate is attributed mainly to close and prolonged exposures during long bus drives. Masking, distancing and personal responsibility are required to avoid such outbreaks.

Adjuvanted trivalent influenza vaccine versus quadrivalent inactivated influenza vaccine in Hutterite Children: A randomized clinical trial

BACKGROUND

Children play an important role in the transmission of influenza. The best choice of vaccine to achieve both direct and indirect protection is uncertain. The objective of the study was to test whether vaccinating children with MF59 adjuvanted trivalent influenza vaccine (aTIV) can reduce influenza in children and their extended households compared to inactivated quadrivalent vaccine (QIV).

METHODS

We conducted a cluster randomized trial in 42 Hutterite colonies in Alberta and Saskatchewan. Colonies were randomized such that children were assigned in a blinded manner to receive aTIV (0.25 ml of pediatric aTIV for ages 6 months to < 36 months or 0.5 ml for ages ≥ 36 months to 6 years) or 0.5 ml of QIV. Participants included 424 children aged 6 months to 6 years who received the study vaccine and 1246 family cluster members who did not receive the study vaccine. The primary outcome was confirmed influenza A and B infection using a real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay. An intent to treat analysis was used. Data were collected from January 2017 to June 2019.

RESULTS

The mean percentage of children who received study vaccine was 62% for aTIV colonies and 74% for QIV colonies. There were 66 (3.4%) with RT-PCR confirmed influenza A and B in the aTIV colonies (children and family clusters) versus 93 (4.4%) in the QIV colonies, hazard ratio (HR) 0.78 (95 %CI 0.36-1.71). Of these, 48 (2.5%) in the aTIV colonies and 76 (3.6%) in the QIV colonies had influenza A, HR 0.69, (95 %CI 0.29-1.66) while 18 (0.9%) and 17 (0.8%) in the aTIV versus QIV colonies respectively had influenza B, HR 1.22, (95 %CI 0.20-7.41). In children who received study vaccine, there were 5 Influenza A infections in the aTIV colonies (1.1%) compared to 30 (5.8%) in the QIV colonies, relative efficacy of 80%, HR 0.20, (95 %CI 0.06-0.66). Adverse events were significantly more common among children who received aTIV. No serious vaccine adverse events were reported.

CONCLUSION

Vaccinating children with aTIV compared to QIV resulted in similar community RT-PCR confirmed influenza illness and led to significant protection against influenza A in children.

Incidence of influenza virus infections confirmed by serology in children and adult in a suburb community, northern China, 2018-2019 influenza season

Background

In mainland China, seasonal influenza disease burden at community level is unknown. The incidence rate of influenza virus infections in the community is difficult to determine due to the lack of well‐defined catchment populations of influenza‐like illness surveillance sentinel hospitals.

Objectives

We established a community‐based cohort to estimate incidence of seasonal influenza infections indicated by serology and protection conferred by antibody titers against influenza infections during 2018‐2019 influenza season in northern China.

Methods

We recruited participants in November 2018 and conducted follow‐up in May 2019 with collection of sera every survey. Seasonal influenza infections were indicated by a 4‐fold or greater increase of hemagglutination inhibition (HI) antibody between paired sera.

Results

Two hundred and three children 5‐17 years of age and 413 adults 18‐59 years of age were followed up and provided paired sera. The overall incidence of seasonal influenza infection and incidence of A(H3N2) infection in children (31% and 17%, respectively) were significantly higher than those in adults (21% and 10%, respectively). The incidences of A(H1N1)pdm09 infection in children and adults were both about 10%, while the incidences of B/Victoria and/Yamagata infection in children and adults were from 2% to 4%. HI titers of 1:40 against A(H1N1)pdm09 and A(H3N2) viruses were associated with 63% and 75% protection against infections with the two subtypes, respectively.

Conclusions

In the community, we identified considerable incidence of seasonal influenza infections. A HI titer of 1:40 could be sufficient to provide 50% protection against influenza A virus infections indicated by serology.

Baloxavir Marboxil for Prophylaxis against Influenza in Household Contacts

BACKGROUND

Baloxavir marboxil (baloxavir) is a polymerase acidic protein (PA) endonuclease inhibitor with clinical efficacy in the treatment of uncomplicated influenza, including in outpatients at increased risk for complications. The postexposure prophylactic efficacy of baloxavir in the household setting is unclear.

METHODS

We conducted a multicenter, double-blind, randomized, placebo-controlled trial to evaluate the postexposure prophylactic efficacy of baloxavir in household contacts of index patients with confirmed influenza during the 2018-2019 season in Japan. The participants were assigned in a 1:1 ratio to receive either a single dose of baloxavir or placebo. The primary end point was clinical influenza, as confirmed by reverse-transcriptase-polymerase-chain-reaction testing, over a period of 10 days. The occurrence of baloxavir-selected PA substitutions associated with reduced susceptibility was assessed.

RESULTS

A total of 752 household contacts of 545 index patients were randomly assigned to receive baloxavir or placebo. Among the index patients, 95.6% had influenza A virus infection, 73.6% were younger than 12 years of age, and 52.7% received baloxavir. Among the participants who could be evaluated (374 in the baloxavir group and 375 in the placebo group), the percentage in whom clinical influenza developed was significantly lower in the baloxavir group than in the placebo group (1.9% vs. 13.6%) (adjusted risk ratio, 0.14; 95% confidence interval [CI], 0.06 to 0.30; P<0.001). Baloxavir was effective in high-risk, pediatric, and unvaccinated subgroups of participants. The risk of influenza infection, regardless of symptoms, was lower with baloxavir than with placebo (adjusted risk ratio, 0.43; 95% CI, 0.32 to 0.58). The incidence of adverse events was similar in the two groups (22.2% in the baloxavir group and 20.5% in the placebo group). In the baloxavir group, the viral PA substitutions I38T/M or E23K were detected in 10 (2.7%) and 5 (1.3%) participants, respectively. No transmission of these variants from baloxavir-treated index patients to participants in the placebo group was detected; however, several instances of transmission to participants in the baloxavir group could not be ruled out.

CONCLUSIONS

Single-dose baloxavir showed significant postexposure prophylactic efficacy in preventing influenza in household contacts of patients with influenza. (Funded by Shionogi; Japan Primary Registries Network number, JapicCTI-184180.).

Seasonal Incidence of Symptomatic Influenza in the United States

Background

The seasonal incidence of influenza is often approximated as 5%-20%.

Methods

We used 2 methods to estimate the seasonal incidence of symptomatic influenza in the United States. First, we made a statistical estimate extrapolated from influenza-associated hospitalization rates for 2010-2011 to 2015-2016, collected as part of national surveillance, covering approximately 9% of the United States, and including the existing mix of vaccinated and unvaccinated persons. Second, we performed a literature search and meta-analysis of published manuscripts that followed cohorts of subjects during 1996-2016 to detect laboratory-confirmed symptomatic influenza among unvaccinated persons; we adjusted this result to the US median vaccination coverage and effectiveness during 2010-2016.

Results

The statistical estimate of influenza incidence among all ages ranged from 3.0%-11.3% among seasons, with median values of 8.3% (95% confidence interval [CI], 7.3%-9.7%) for all ages, 9.3% (95% CI, 8.2%-11.1%) for children <18 years, and 8.9% (95% CI, 8.2%-9.9%) for adults 18-64 years. Corresponding values for the meta-analysis were 7.1% (95% CI, 6.1%-8.1%) for all ages, 8.7% (95% CI, 6.6%-10.5%) for children, and 5.1% (95% CI, 3.6%-6.6%) for adults.

Conclusions

The 2 approaches produced comparable results for children and persons of all ages. The statistical estimates are more versatile and permit estimation of season-to-season variation. During 2010-2016, the incidence of symptomatic influenza among vaccinated and unvaccinated US residents, including both medically attended and nonattended infections, was approximately 8% and varied from 3% to 11% among seasons.

Effectiveness of seasonal inactivated influenza vaccination in Japanese schoolchildren: an epidemiologic study at the community level

Influenza vaccination is the most effective method for preventing influenza virus infection. The incidence of influenza is higher in schoolchildren than other age groups. This study evaluated the effectiveness of seasonal inactivated influenza vaccination (IIV) in a community population of schoolchildren during two seasons. This study was a cross-sectional survey of public schoolchildren based on data collected in the 2012/2013 and 2014/2015 seasons. The questionnaire was distributed to all public schoolchildren of target grade in a survey area, and 7945 respondents were included in the analysis. The vaccination status and influenza onset were defined based on the self-reported questionnaire by parents or guardians. Generalized linear mixed models were used to adjust clustering within schools and individual covariates and calculate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between vaccination status and influenza onset. The influenza incidence was higher in the 2015 than the 2013 survey (25% versus 17%), although the vaccination rates were comparable between the two seasons. Receiving one- or two-dose vaccination was more protective against influenza than non-vaccination in both the 2013 (OR, 0.77; 95%CI, 0.65-0.92) and 2015 (OR, 0.88; 95%CI, 0.75-1.02) surveys. Full vaccination was also more protective in both the 2013 (OR, 0.75; 95%CI, 0.62-0.89) and 2015 (OR, 0.86; 95%CI, 0.74-1.00) surveys. Seasonal IIV was protective against influenza for Japanese schoolchildren in a community-based real-world setting. The difference in clinical effectiveness of IIV between the two seasons was likely due to the antigenic mismatch between the circulating and vaccine strains.

Comparative Immunogenicity of the 2014-2015 Northern Hemisphere Trivalent IIV and LAIV against Influenza A Viruses in Children

Both inactivated influenza vaccines (IIV) and live-attenuated influenza vaccines (LAIV) have been recommended for administration to children. Children are a high-risk group for severe influenza, and a major source of transmission. Therefore, prevention of infection by vaccination is particularly important. However, efficacy and immunogenicity of these vaccines are known to vary by season and geographic location. We compared the immunogenicity of the 2014–2015 Northern Hemisphere trivalent IIV and LAIV against influenza A virus in Canadian Hutterite children aged 2 to 17 using hemagglutination inhibition (HAI) assays, and enzyme-linked immunosorbent assays to measure hemagglutinin-specific serum IgA and mucosal IgA. Both vaccine formulations induced significant increases in HAI titers against H1N1 and H3N2 vaccine strains. Serum IgA titers against H3N2 were significantly boosted by both IIV and LAIV, while only IIV induced a significant increase in serum IgA specific to the H1N1 vaccine strain. While HAI titers correlated with protection conferred by IIV, mucosal IgA titers correlated with protection conferred by LAIV (mucosal IgA titers could not be established as a correlate for IIV due to sample size limitations). IIV and LAIV were previously reported to be equally efficacious in this cohort, although the immunogenicity of IIV was generally superior.

Racial/Ethnic Disparities in Influenza Vaccination Coverage Among US Adolescents, 2010-2016

OBJECTIVE

Although research suggests racial/ethnic disparities in influenza vaccination and mortality rates, few studies have examined racial/ethnic trends among US adolescents. We used national cross-sectional data to determine (1) trends in influenza vaccination rates among non-Hispanic white (hereinafter, white), non-Hispanic black (hereinafter, black), and Hispanic adolescents over time and (2) whether influenza vaccination rates among adolescents varied by race/ethnicity.

METHODS

We analyzed provider-reported vaccination histories for 2010-2016 from the National Immunization Survey-Teen. We used binary logistic regression models to determine trends in influenza vaccination rates by race/ethnicity for 117 273 adolescents, adjusted for sex, age, health insurance, physician visit in the previous 12 months, vaccination facility type, poverty status, maternal education level, children in the household, maternal marital status, maternal age, and census region of residence. We calculated adjusted probabilities for influenza vaccination for each racial/ethnic group, adjusted for the same demographic characteristics.

RESULTS

Compared with white adolescents, Hispanic adolescents had higher odds (adjusted odds ratio [aOR] = 1.11; 95% confidence interval [CI], 1.06-1.16) and black adolescents had lower odds (aOR = 0.95; 95% CI, 0.90-1.00) of vaccination. Compared with white adolescents, Hispanic adolescents had significantly higher adjusted probabilities of vaccination for 2011-2013 (2011: 0.22, P < .001; 2012: 0.23, P < .001; 2013: 0.26, P < .001). Compared with white adolescents, black adolescents had significantly lower probabilities of vaccination for 2016 (2016: 0.21, P < .001).

CONCLUSIONS

Targeted interventions are needed to improve adolescent influenza vaccination rates and reduce racial/ethnic disparities in adolescent vaccination coverage.

The Role of Sociodemographic and Psychological Variables on Risk Perception of the Flu

Influenza is a source of mortality and morbidity, and vigilance of health authorities for flu viruses is high. The World Health Organization (WHO) highlighted that the first lines of defense against infectious diseases are behavioral, and risk perception affects behavioral measures. This study investigated risk perception of influenza and the role of sociodemographic and psychological variables on perceived risk. Participants were 442 adults. The research was conducted using three measures: an adjustment of the "Risk Perception of Infectious Disease Questionnaire," the "General Self-Efficacy Scale," and the short form of the "Italian Personality Inventory." The results showed that age, education, self-efficacy, and personality influenced risk perception. The evidence that sociodemographic and psychological factors contribute to risk perception of a disease shows the need to take into account these variables in the planning of informative campaigns, with the aim to achieve favorable changes in public behavior. These issues might have implications for the ameliorating health communication efforts and successful response to new influenza outbreaks.

The presence of fever in adults with influenza and other viral respiratory infections

We compared the rates of fever in adult subjects with laboratory-confirmed influenza and other respiratory viruses and examined the factors that predict fever in adults. Symptom data on 158 healthcare workers (HCWs) with a laboratory-confirmed respiratory virus infection were collected using standardized data collection forms from three separate studies. Overall, the rate of fever in confirmed viral respiratory infections in adult HCWs was 23·4% (37/158). Rates varied by virus: human rhinovirus (25·3%, 19/75), influenza A virus (30%, 3/10), coronavirus (28·6%, 2/7), human metapneumovirus (28·6%, 2/7), respiratory syncytial virus (14·3%, 4/28) and parainfluenza virus (8·3%, 1/12). Smoking [relative risk (RR) 4·65, 95% confidence interval (CI) 1·33-16·25] and co-infection with two or more viruses (RR 4·19, 95% CI 1·21-14·52) were significant predictors of fever. Fever is less common in adults with confirmed viral respiratory infections, including influenza, than described in children. More than 75% of adults with a viral respiratory infection do not have fever, which is an important finding for clinical triage of adult patients with respiratory infections. The accepted definition of 'influenza-like illness' includes fever and may be insensitive for surveillance when high case-finding is required. A more sensitive case definition could be used to identify adult cases, particularly in event of an emerging viral infection.

Mechanisms of replacement of circulating viruses by seasonal and pandemic influenza A viruses

BACKGROUND

Seasonal influenza causes annual epidemics by the accumulation of antigenic changes. Pandemic influenza occurs through a major antigenic change of the influenza A virus, which can originate from other hosts. Although new antigenic variants of the influenza A virus replace formerly circulating seasonal and pandemic viruses, replacement mechanisms remain poorly understood.

METHODS

A stochastic individual-based SEIR (susceptible-exposed-infectious-recovered) model with two viral strains (formerly circulating old strain and newly emerged strain) was developed for simulations to elucidate the replacement mechanisms.

RESULTS

Factors and conditions of virus and host populations affecting the replacement were identified. Replacement is more likely to occur in tropical regions than temperate regions. The magnitude of the ongoing epidemic by the old strain, herd immunity against the old strain, and timing of appearance of the new strain are not that important for replacement. It is probable that the frequency of replacement by a pandemic virus is higher than a seasonal virus because of the high initial susceptibility and high basic reproductive number of the pandemic virus.

CONCLUSIONS

The findings of this study on replacement mechanisms could lead to a better understanding of virus transmission dynamics and may possibly be helpful in establishing an effective strategy to mitigate the impact of seasonal and pandemic influenza.

Household Transmission of Influenza Virus

Human influenza viruses cause regular epidemics and occasional pandemics with a substantial public health burden. Household transmission studies have provided valuable information on the dynamics of influenza transmission. We reviewed published studies and found that once one household member is infected with influenza, the risk of infection in a household contact can be up to 38%, and the delay between onset in index and secondary cases is around 3 days. Younger age was associated with higher susceptibility. In the future, household transmission studies will provide information on transmission dynamics, including the correlation of virus shedding and symptoms with transmission, and the correlation of new measures of immunity with protection against infection.

Historically, household cohort studies have provided valuable information on the incidence of respiratory infections and risk factors for infection. However, these studies require substantial resources and can provide limited information on transmission dynamics.

Household transmission studies provide an efficient approach to describing the risk of influenza transmission and factors affecting transmission. In these studies, households with at least one member infected by influenza are eligible and are followed intensively for 1–2 weeks to observe secondary transmission within the household.

Transmission studies also provide a model for evaluation of interventions in randomized controlled trials, and have been used to determine the efficacy of antiviral drugs for treatment and prophylaxis, and nonpharmaceutical interventions such as face masks and hand hygiene.

Global circulation patterns of seasonal influenza viruses vary with antigenic drift

Understanding the spatio-temporal patterns of emergence and circulation of new human seasonal influenza virus variants is a key scientific and public health challenge. The global circulation patterns of influenza A/H3N2 viruses are well-characterized^1-7 but the patterns of A/H1N1 and B viruses have remained largely unexplored. Here, based on analyses of 9,604 hemagglutinin sequences of human seasonal influenza viruses from 2000–2012, we show that the global circulation patterns of A/H1N1 (up to 2009), B/Victoria, and B/Yamagata viruses differ substantially from those of A/H3N2 viruses. While genetic variants of A/H3N2 viruses did not persist locally between epidemics and were reseeded from East and Southeast (E-SE) Asia, genetic variants of A/H1N1 and B viruses persisted across multiple seasons and exhibited complex global dynamics with E-SE Asia playing a limited role in disseminating new variants. The less frequent global movement of influenza A/H1N1 and B viruses coincided with slower rates of antigenic evolution, lower ages of infection, and smaller less frequent epidemics compared to A/H3N2 viruses. Detailed epidemic models support differences in age of infection, combined with the less frequent travel of children, as likely drivers of the differences in the patterns of global circulation, suggesting a complex interaction between virus evolution, epidemiology and human behavior.

Effectiveness of primary care-public health collaborations in the delivery of influenza vaccine: a cluster-randomized pragmatic trial

OBJECTIVE

To assess effectiveness and feasibility of public-private collaboration in delivering influenza immunization to children.

METHODS

Four pediatric and four family medicine (FM) practices in Colorado with a common public health department (PHD) were randomized at the beginning of baseline year (10/2009) to Intervention (joint community clinics and PHD nurses aiding in delivery at practices); or control involving usual care without PHD. Generalized estimating equations compared changes in rates over baseline between intervention and control practices at end of 2nd intervention year (Y2=5/2011). Barriers to collaboration were examined using qualitative methods.

RESULTS

Overall, rates increased from baseline to Y2 by 9.2% in intervention and 3.2% in control (p<.0001), with significant increases in both pediatric and FM practices. The largest increases were seen among school-aged and adolescent children (p<.0001 for both), with differences for 6-month-old to 5-year-old children and for children with high-risk conditions not reaching significance. Barriers to collaboration included uncertainty regarding the delivery of vaccine supplies, concerns about using up all purchased vaccine by practices, and concerns about documentation of vaccination if collaboration occurred.

CONCLUSIONS

In spite of barriers, public-private collaboration resulted in significantly higher influenza immunization rates, particularly for older, healthy children who visit providers less frequently.

A model-based economic analysis of pre-pandemic influenza vaccination cost-effectiveness

Background

A vaccine matched to a newly emerged pandemic influenza virus would require a production time of at least 6 months with current proven techniques, and so could only be used reactively after the peak of the pandemic. A pre-pandemic vaccine, although probably having lower efficacy, could be produced and used pre-emptively. While several previous studies have investigated the cost effectiveness of pre-emptive vaccination strategies, they have not been directly compared to realistic reactive vaccination strategies.

Methods

An individual-based simulation model of ~30,000 people was used to examine a pre-emptive vaccination strategy, assuming vaccination conducted prior to a pandemic using a low-efficacy vaccine. A reactive vaccination strategy, assuming a 6-month delay between pandemic emergence and availability of a high-efficacy vaccine, was also modelled. Social distancing and antiviral interventions were examined in combination with these alternative vaccination strategies. Moderate and severe pandemics were examined, based on estimates of transmissibility and clinical severity of the 1957 and 1918 pandemics respectively, and the cost effectiveness of each strategy was evaluated.

Results

Provided that a pre-pandemic vaccine achieved at least 30% efficacy, pre-emptive vaccination strategies were found to be more cost effective when compared to reactive vaccination strategies. Reactive vaccination coupled with sustained social distancing and antiviral interventions was found to be as effective at saving lives as pre-emptive vaccination coupled with limited duration social distancing and antiviral use, with both strategies saving approximately 420 life-years per 10,000 population for a moderate pandemic with a basic reproduction number of 1.9 and case fatality rate of 0.25%. Reactive vaccination was however more costly due to larger productivity losses incurred by sustained social distancing, costing $8 million per 10,000 population ($19,074/LYS) versus $6.8 million per 10,000 population ($15,897/LYS) for a pre-emptive vaccination strategy. Similar trends were observed for severe pandemics.

Conclusions

Compared to reactive vaccination, pre-emptive strategies would be more effective and more cost effective, conditional on the pre-pandemic vaccine being able to achieve a certain level of coverage and efficacy. Reactive vaccination strategies exist which are as effective at mortality reduction as pre-emptive strategies, though they are less cost effective.

Factors associated with receipt of 2009 pandemic influenza A (H1N1) monovalent and seasonal influenza vaccination among school-aged children: Maricopa County, Arizona, 2009-2010 influenza season

CONTEXT

To target school-aged children (SAC), who were identified as a priority for pandemic 2009 Influenza A (pH1N1) vaccination, Maricopa County (MC) initiated school-based influenza vaccination in 69% of its 706 schools during the 2009-2010 influenza season.

OBJECTIVE

To determine factors associated with receipt of pH1N1 monovalent and 2009-2010 seasonal influenza vaccination among SAC and evaluate the association of school-based vaccination with vaccination status of SAC.

DESIGN

Random-digit dialing was used to survey 600 MC households with willing adult participants and children grades K-12. Logistic regression was used to identify factors associated with pH1N1 and seasonal vaccine receipt.

SETTING

Arizona.

PARTICIPANTS

Household adults with children grades K-12.

MAIN OUTCOME MEASURE

Characteristics of children, parents, and households were obtained.

RESULTS

Among 909 SAC, 402 (44%) received pH1N1 and 436 (48%) received seasonal vaccination. Factors associated with pH1N1 vaccination included vaccine availability at school (adjusted odds ratio [AOR]: 1.6; 95% confidence interval [CI]: 1.0-2.7), high-risk medical condition in child (AOR: 2.4; 95% CI: 1.4-4.0), elementary versus high school attendance (AOR: 1.6; 95% CI: 1.0-2.7), and seasonal influenza vaccination (AOR: 10.0; 95% CI: 6.4-15.6). Factors associated with seasonal vaccination included Hispanic ethnicity (AOR: 2.2; 95% CI: 1.1-4.2), health insurance coverage (AOR: 4.8; 95% CI: 1.7-13.7), elementary versus high school attendance (AOR: 1.5; 95% CI: 1.0-2.5), and pH1N1 vaccination (AOR: 10.5; 95% CI: 6.7-16.6).

CONCLUSIONS

Availability of pH1N1 vaccine at school was independently associated with pH1N1 vaccination of MC school-aged children. School-based influenza vaccination campaigns should be considered to increase vaccination among this population.

School-located influenza vaccination with third-party billing: outcomes, cost, and reimbursement

OBJECTIVE

To assess rates of immunization; costs of conducting clinics; and reimbursements for a school-located influenza vaccination (SLIV) program that billed third-party payers.

METHODS

SLIV clinics were conducted in 19 elementary schools in the Denver Public School district (September 2010 to February 2011). School personnel obtained parental consent, and a community vaccinator conducted clinics and performed billing. Vaccines For Children vaccine was available for eligible students. Parents were not billed for any fees. Data were collected regarding implementation costs and vaccine cost was calculated using published private sector prices. Reimbursement amounts were compared to costs.

RESULTS

Overall, 30% of students (2784 of 9295) received ≥1 influenza vaccine; 39% (1079 of 2784) needed 2 doses and 80% received both. Excluding vaccine costs, implementation costs were $24.69 per vaccination. The percentage of vaccine costs reimbursed was 62% overall (82% from State Child Health Insurance Program (SCHIP), 50% from private insurance). The percentage of implementation costs reimbursed was 19% overall (23% from private, 27% from Medicaid, 29% from SCHIP and 0% among uninsured). Overall, 25% of total costs (implementation plus vaccine) were reimbursed.

CONCLUSIONS

A SLIV program resulted in vaccination of nearly one third of elementary students. Reimbursement rates were limited by 1) school restrictions on charging parents fees, 2) low payments for vaccine administration from public payers and 3) high rates of denials from private insurers. Some of these problems might be reduced by provisions in the Affordable Care Act.

Effectiveness and safety of seasonal influenza vaccination in children with underlying respiratory diseases and allergy

Influenza causes acute respiratory infections and various complications. Children in the high-risk group have higher complication and hospitalization rates than high-risk elderly individuals. Influenza prevention in children is important, as they can be a source infection spread in their communities. Influenza vaccination is strongly recommended for high-risk children with chronic underlying circulatory and respiratory disease, immature infants, and children receiving long-term immunosuppressant treatment or aspirin. However, vaccination rates in these children are low because of concerns regarding the exacerbation of underlying diseases and vaccine efficacy. To address these concerns, many clinical studies on children with underlying respiratory diseases have been conducted since the 1970s. Most of these reported no differences in immunogenicity or adverse reactions between healthy children and those with underlying respiratory diseases and no adverse effects of the influenza vaccine on the disease course. Further to these studies, the inactivated split-virus influenza vaccine is recommended for children with underlying respiratory disease, in many countries. However, the live-attenuated influenza vaccine (LAIV) is not recommended for children younger than 5 years with asthma or recurrent wheezing. Influenza vaccination is contraindicated in patients with severe allergies to egg, chicken, or feathers, because egg-cultivated influenza vaccines may contain ovalbumin. There has been no recent report of serious adverse events after influenza vaccination in children with egg allergy. However, many experts recommend the trivalent influenza vaccine for patients with severe egg allergy, with close observation for 30 minutes after vaccination. LAIV is still not recommended for patients with asthma or egg allergy.

Association between antibody titers and protection against influenza virus infection within households

BACKGROUND

Previous studies have established that antibody titer measured by the hemagglutination-inhibiting (HAI) assay is correlated with protection against influenza virus infection, with an HAI titer of 1:40 generally associated with 50% protection.

METHODS

We recruited index cases with confirmed influenza virus infection from outpatient clinics, and followed up their household contacts for 7-10 days to identify secondary infections. Serum samples collected from a subset of household contacts were tested by HAI and microneutralization (MN) assays against prevalent influenza viruses. We analyzed the data using an individual hazard-based transmission model that adjusted for age and vaccination history.

RESULTS

Compared to a reference group with antibody titers <1:10, we found that HAI titers of 1:40 against influenza A(H1N1) and A(H3N2) were associated with 31% (95% confidence interval [CI], 13%-46%) and 31% (CI, 1%-53%) protection against polymerase chain reaction (PCR)-confirmed A(H1N1) and A(H3N2) virus infection, respectively, while an MN titer of 1:40 against A(H3N2) was associated with 49% (95% CI, 7%-81%) protection against PCR-confirmed A(H3N2) virus infection.

CONCLUSIONS

An HAI titer of 1:40 was associated with substantially less than 50% protection against PCR-confirmed influenza virus infection within households, perhaps because of exposures of greater duration or intensity in that confined setting.

Asymptomatic ratio for seasonal H1N1 influenza infection among schoolchildren in Taiwan

Background

Studies indicate that asymptomatic infections do indeed occur frequently for both seasonal and pandemic influenza, accounting for about one-third of influenza infections. Studies carried out during the 2009 pH1N1 pandemic have found significant antibody response against seasonal H1N1 and H3N2 vaccine strains in schoolchildren receiving only pandemic H1N1 monovalent vaccine, yet reported either no symptoms or only mild symptoms.

Methods

Serum samples of 255 schoolchildren, who had not received vaccination and had pre-season HI Ab serotiters <40, were collected from urban, rural areas and an isolated island in Taiwan during the 2005–2006 influenza season. Their hemagglutination inhibition antibody (HI Ab) serotiters against the 2005 A/New Caledonia/20/99 (H1N1) vaccine strain at pre-season and post-season were measured to determine the symptoms with the highest correlation with infection, as defined by 4-fold rise in HI titer. We estimate the asymptomatic ratio, or the proportion of asymptomatic infections, for schoolchildren during the 2005–6 influenza season when this vaccine strain was found to be antigenically related to the circulating H1N1 strain.

Results

Fever has the highest correlation with the 2005–06 seasonal influenza A(H1N1) infection, followed by headache, cough, vomiting, and sore throat. Asymptomatic ratio for the schoolchildren is found to range between 55.6% (95% CI: 44.7-66.4)-77.9% (68.8-87.0) using different sets of predictive symptoms. Moreover, the asymptomatic ratio was 66.9% (56.6-77.2) when using US-CDC criterion of fever + (cough/sore throat), and 73.0 (63.3-82.8) when under Taiwan CDC definition of Fever + (cough or sore throat or nose) + ( headache or pain or fatigue).

Conclusions

Asymptomatic ratio for children is found to be substantially higher than that of the general population in literature. In providing reasonable quantification of the asymptomatic infected children spreading pathogens to others in a seasonal epidemic or a pandemic, our estimates of symptomatic ratio of infected children has important clinical and public health implications.

Immunogenicity of influenza vaccine in colorectal cancer patients

Purpose

Although influenza is regarded as a major cause of morbidity and mortality in immunocompromised patients, vaccine coverage remains poor. We evaluated the immunogenicity of influenza vaccines in colorectal cancer patients.

Materials and Methods

In this study, 40 colorectal cancer patients who received an influenza vaccine at the Korea Cancer Center Hospital during the 2009-2010 and 2010-2011 influenza seasons were analyzed. The blood samples were collected at prevaccination and 30 days post vaccination, and antibody titers were measured using the hemagglutination-inhibition tests.

Results

In the 2009-2011 season, the seroprotection rate for H1N1 (94.7%) was significantly higher than that for H3N2 (42.1%) and B (47.3%). The seroconversion rate was 52.6%, 26.3%, and 36.8% for H1N1, H3N2, and B, respectively. Fold increase of geometric mean titer (MFI) was 3.86, 1.49, and 3.33 for H1N1, H3N2, and B, respectively. In the 2010-2011 season, the seroprotection rate for H1N1 (57.1%) was significantly higher than that for H3N2 (52.4%) and B (38.1%). The seroconversion rate was 52.4%, 47.6% and 33.3% for H1N1, H3N2, and B, respectively. MFI was 12.29, 3.62 and 4.27 for H1N1, H3N2, and B, respectively.

Conclusion

Our study cohort showed an acceptable immune response to an influenza vaccine without significant adverse effects, supporting the recommendation for annual influenza vaccination in colorectal cancer patients.

Description of a school nurse visit syndromic surveillance system and comparison to emergency department visits, New York City

OBJECTIVES

We compared school nurse visit syndromic surveillance system data to emergency department (ED) visit data for monitoring illness in New York City schoolchildren.

METHODS

School nurse visit data recorded in an electronic health record system are used to conduct daily surveillance of influenza-like illness, fever-flu, allergy, asthma, diarrhea, and vomiting syndromes. We calculated correlation coefficients to compare the percentage of syndrome visits to the school nurse and ED for children aged 5 to 14 years, from September 2006 to June 2011.

RESULTS

Trends in influenza-like illness correlated significantly (correlation coefficient = 0.89; P < .001) and 72% of school signals occurred on days that ED signaled. Trends in allergy (correlation coefficient = 0.73; P < .001) and asthma (correlation coefficient = 0.56; P < .001) also correlated and school signals overlapped with ED signals on 95% and 51% of days, respectively. Substantial daily variation in diarrhea and vomiting visits limited our ability to make comparisons.

CONCLUSIONS

Compared with ED syndromic surveillance, the school nurse system identified similar trends in influenza-like illness, allergy, and asthma syndromes. Public health practitioners without school-based surveillance may be able to use age-specific analyses of ED syndromic surveillance data to monitor illness in schoolchildren.

Influenza-associated pediatric deaths in the United States, 2004-2012

BACKGROUND

Influenza-associated deaths in children occur annually. We describe the epidemiology of influenza-associated pediatric deaths from the 2004-2005 through the 2011-2012 influenza seasons.

METHODS

Deaths in children <18 years of age with laboratory-confirmed influenza virus infection were reported to the Centers for Disease Control and Prevention by using a standard case report form to collect data on demographic characteristics, medical conditions, clinical course, and laboratory results. Characteristics of children with no high-risk medical conditions were compared with those of children with high-risk medical conditions.

RESULTS

From October 2004 through September 2012, 830 pediatric influenza-associated deaths were reported. The median age was 7 years (interquartile range: 1-12 years). Thirty-five percent of children died before hospital admission. Of 794 children with a known medical history, 43% had no high-risk medical conditions, 33% had neurologic disorders, and 12% had genetic or chromosomal disorders. Children without high-risk medical conditions were more likely to die before hospital admission (relative risk: 1.9; 95% confidence interval: 1.6-2.4) and within 3 days of symptom onset (relative risk: 1.6; 95% confidence interval: 1.3-2.0) than those with high-risk medical conditions.

CONCLUSIONS

Influenza can be fatal in children with and without high-risk medical conditions. These findings highlight the importance of recommendations that all children should receive annual influenza vaccination to prevent influenza, and children who are hospitalized, who have severe illness, or who are at high risk of complications (age <2 years or with medical conditions) should receive antiviral treatment as early as possible.

Understanding reasons for participating in a school-based influenza vaccination program and decision-making dynamics among adolescents and parents

Influenza remains a significant cause of morbidity and mortality in the United States. Vaccinating school-aged children has been demonstrated to be beneficial to the child and in reducing viral transmission to vulnerable groups such as the elderly. This qualitative study sought to identify reasons parents and students participated in a school-based influenza vaccination clinic and to characterize the decision-making process for vaccination. Eight focus groups were conducted with parents and students. Parents and students who participated in the influenza vaccination clinic stated the educational brochure mailed to their home influenced participation in the program. Parents of non-participating students mentioned barriers, such as the lengthy and complicated consent process and suspicions about the vaccine clinic, as contributing to their decision not to vaccinate their child. Vaccinated students reported initiating influenza vaccine discussion with their parents. Parental attitudes and the educational material influenced parents' decision to allow their child to receive influenza vaccine. This novel study explored reasons for participating in a school-based vaccination clinic and the decision-making process between parents and child(ren). Persons running future school-based vaccination clinics may consider hosting an 'information session with a question and answer session' to address parental concerns and assist with the consent process.

Laninamivir octanoate for post-exposure prophylaxis of influenza in household contacts: a randomized double blind placebo controlled trial

Laninamivir octanoate, a long-acting neuraminidase inhibitor, is an effective treatment for influenza. However, its effectiveness for the prevention of influenza has not yet been demonstrated. We conducted a double-blind, multicenter, randomized, placebo-controlled trial to determine whether laninamivir octanoate was superior to a placebo for post-exposure prophylaxis of influenza in household contacts. Eligible participants, who were household members who did not have influenza and were in contact with an influenza-infected index patient, were randomly assigned (1:1:1) to one of three groups: 20 mg of laninamivir octanoate once daily for 2 days (LO-2), 20 mg of laninamivir octanoate once daily for 3 days (LO-3), or a placebo. The primary endpoint was the proportion of participants who developed clinical influenza during a 10-day period. A total of 1711 participants were enrolled, and 1451 participants were included in the primary analysis. The proportion of participants with clinical influenza was 3.9 % (19/487) in the LO-2 group, 3.7 % (18/486) in the LO-3 group, and 16.9 % (81/478) in the placebo group (P < 0.001 for each of the laninamivir octanoate group). The relative risk reductions, compared with the placebo group, were 77.0 % [95 % confidence interval (CI) 62.7-85.8] and 78.1 % (95 % CI 64.1-86.7 %) for the LO-2 and LO-3 groups, respectively. The incidences of adverse events in the laninamivir octanoate groups were similar to that in the placebo group. The inhalation of 20 mg of laninamivir octanoate once daily for 2 or 3 days was well tolerated and effectively prevented the development of influenza in household contacts.

Immunobiology of influenza vaccines

Vaccination is the primary strategy for prevention and control of influenza. The surface hemagglutinin (HA) protein of the influenza virus contains two structural elements (head and stalk) that differ in their potential utility as vaccine targets. The head of the HA protein is the primary target of antibodies that confer protective immunity to influenza viruses. The underlying health status, age, and gene polymorphisms of vaccine recipients and, just as importantly, the extent of the antigenic match between the viruses in the vaccine and those that are circulating modulate influenza vaccine protection. Vaccine adjuvants and live attenuated influenza vaccine improve the breadth of immunity to seasonal and pandemic virus strains. Eliciting antibodies against the conserved HA stem region that cross-react with HAs within influenza virus types or subtypes would allow for the development of a universal influenza vaccine. The highly complex network of interactions generated after influenza infection and vaccination can be studied with the use of systems biology tools, such as DNA microarray chips. The use of systems vaccinology has allowed for the generation of gene expression signatures that represent key transcriptional differences between asymptomatic and symptomatic host responses to influenza infection. Additionally, the use of systems vaccinology tools have resulted in the identification of novel surrogate gene markers that are predictors of the magnitude of host responses to vaccines, which is critical to both vaccine development and public health. Identifying associations between variations in vaccine immune responses and gene polymorphisms is critical in the development of universal influenza vaccines.

Assessing parents' knowledge and attitudes towards seasonal influenza vaccination of children before and after a seasonal influenza vaccination effectiveness study in low-income urban and rural Kenya, 2010-2011

Background

Influenza vaccine is rarely used in Kenya, and little is known about attitudes towards the vaccine. From June-September 2010, free seasonal influenza vaccine was offered to children between 6 months and 10 years old in two Population-Based Infectious Disease Surveillance (PBIDS) sites. This survey assessed attitudes about influenza, uptake of the vaccine and experiences with childhood influenza vaccination.

Methods

We administered a questionnaire and held focus group discussions with parents of children of enrollment age in the two sites before and after first year of the vaccine campaign. For pre-vaccination focus group discussions, we randomly selected mothers and fathers who had an eligible child from the PBIDS database to participate. For the post-vaccination focus group discussions we stratified parents whose children were eligible for vaccination into fully vaccinated, partially vaccinated and non-vaccinated groups.

Results

Overall, 5284 and 5755 people completed pre and post-vaccination questionnaires, respectively, in Kibera and Lwak. From pre-vaccination questionnaire results, among parents who were planning on vaccinating their children, 2219 (77.6%) in Kibera and 1780 (89.6%) in Lwak said the main reason was to protect the children from seasonal influenza. In the pre-vaccination discussions, no parent had heard of the seasonal influenza vaccine. At the end of the vaccine campaign, of 18,652 eligible children, 5,817 (31.2%) were fully vaccinated, 2,073 (11.1%) were partially vaccinated and, 10,762 (57.7%) were not vaccinated. In focus group discussions, parents who declined vaccine were concerned about vaccine safety or believed seasonal influenza illness was not severe enough to warrant vaccination. Parents who declined the vaccine were mainly too busy [251(25%) in Kibera and 95 (10.5%) in Lwak], or their child was away during the vaccination period [199(19.8%) in Kibera; 94(10.4%) in Lwak].

Conclusion

If influenza vaccine were to be introduced more broadly in Kenya, effective health messaging will be needed on vaccine side effects and frequency and potential severity of influenza infection.

The cost effectiveness of pandemic influenza interventions: a pandemic severity based analysis

BACKGROUND

The impact of a newly emerged influenza pandemic will depend on its transmissibility and severity. Understanding how these pandemic features impact on the effectiveness and cost effectiveness of alternative intervention strategies is important for pandemic planning.

METHODS

A cost effectiveness analysis of a comprehensive range of social distancing and antiviral drug strategies intended to mitigate a future pandemic was conducted using a simulation model of a community of ∼30,000 in Australia. Six pandemic severity categories were defined based on case fatality ratio (CFR), using data from the 2009/2010 pandemic to relate hospitalisation rates to CFR.

RESULTS

Intervention strategies combining school closure with antiviral treatment and prophylaxis are the most cost effective strategies in terms of cost per life year saved (LYS) for all severity categories. The cost component in the cost per LYS ratio varies depending on pandemic severity: for a severe pandemic (CFR of 2.5%) the cost is ∼$9 k per LYS; for a low severity pandemic (CFR of 0.1%) this strategy costs ∼$58 k per LYS; for a pandemic with very low severity similar to the 2009 pandemic (CFR of 0.03%) the cost is ∼$155 per LYS. With high severity pandemics (CFR >0.75%) the most effective attack rate reduction strategies are also the most cost effective. During low severity pandemics costs are dominated by productivity losses due to illness and social distancing interventions, while for high severity pandemics costs are dominated by hospitalisation costs and productivity losses due to death.

CONCLUSIONS

The most cost effective strategies for mitigating an influenza pandemic involve combining sustained social distancing with the use of antiviral agents. For low severity pandemics the most cost effective strategies involve antiviral treatment, prophylaxis and short durations of school closure; while these are cost effective they are less effective than other strategies in reducing the infection rate.

Attitudes toward and factors affecting influenza vaccination among physicians and nurses of a tertiary-care hospital in the Central Anatolia region of Turkey

AIM

Similar to most international health care organizations, the Turkish Ministry of Health strongly recommends influenza vaccination for health care professionals. The aim of this study was to assess the vaccination rates and attitudes of physicians and nurses during the 2011 to 2012 seasonal influenza vaccination at a tertiary-care hospital of the Turkish Ministry of Health.

METHODS

This was a descriptive cross-sectional study. The study participants were physicians and nurses working at the Konya Training and Research Hospital, located in the Central Anatolia region of Turkey. Self-reported (anonymous) questionnaires were given to 192 physicians and 411 nurses (N = 603) who agreed to participate between November 1 and 30, 2011. Frequencies, percentages, chi-square tests, and logistic regression tests were used for statistical analyses.

RESULTS

Women comprised 64.1% (n = 387) of the participants, and 63% (n = 380) of participants had been working for ≥ 5 years. The seasonal influenza vaccination rate for all participants during the 2011 to 2012 season was 16.7% (n = 101). Although 9.5% (n = 57) of the study group had a chronic disease, 71.9% (n = 41) did not receive influenza vaccination (P < 0.05). Additionally, 40.8% (n = 240) reported ≥ 2 cases of influenza annually, and 82.9% (n = 204) had not been vaccinated. For 12.9% (n = 78) of participants, influenza caused absenteeism from work. Approximately 45% (n = 271) of participants had never been vaccinated, 27% (n = 163) were vaccinated in 2010, and 21.2% (n = 128) planned on being vaccinated in 2012. Among the vaccinated group, 56.4% (n = 57) experienced no side effects, 29.7% (n = 30) experienced local side effects, and 22.8% (n = 23) developed influenza-like syndrome.

CONCLUSION

Similar to other studies in the literature, vaccination rates were not at the desired level. According to our Hospital Infection Committee reports, vaccination rates at our hospital were lower compared with vaccination rates of the 2009 H1N1 pandemic. The underlying causes of health care professionals abstaining from influenza vaccination should be further evaluated.

Economic analysis of pandemic influenza mitigation strategies for five pandemic severity categories

BACKGROUND

The threat of emergence of a human-to-human transmissible strain of highly pathogenic influenza A(H5N1) is very real, and is reinforced by recent results showing that genetically modified A(H5N1) may be readily transmitted between ferrets. Public health authorities are hesitant in introducing social distancing interventions due to societal disruption and productivity losses. This study estimates the effectiveness and total cost (from a societal perspective, with a lifespan time horizon) of a comprehensive range of social distancing and antiviral drug strategies, under a range of pandemic severity categories.

METHODS

An economic analysis was conducted using a simulation model of a community of ~30,000 in Australia. Data from the 2009 pandemic was used to derive relationships between the Case Fatality Rate (CFR) and hospitalization rates for each of five pandemic severity categories, with CFR ranging from 0.1% to 2.5%.

RESULTS

For a pandemic with basic reproduction number R0 = 1.8, adopting no interventions resulted in total costs ranging from $441 per person for a pandemic at category 1 (CFR 0.1%) to $8,550 per person at category 5 (CFR 2.5%). For severe pandemics of category 3 (CFR 0.75%) and greater, a strategy combining antiviral treatment and prophylaxis, extended school closure and community contact reduction resulted in the lowest total cost of any strategy, costing $1,584 per person at category 5. This strategy was highly effective, reducing the attack rate to 5%. With low severity pandemics costs are dominated by productivity losses due to illness and social distancing interventions, whereas higher severity pandemic costs are dominated by healthcare costs and costs arising from productivity losses due to death.

CONCLUSIONS

For pandemics in high severity categories the strategies with the lowest total cost to society involve rigorous, sustained social distancing, which are considered unacceptable for low severity pandemics due to societal disruption and cost.

Estimating influenza incidence and rates of influenza-like illness in the outpatient setting

Please cite this paper as: Fowlkes et al. (2012) Estimating influenza incidence and rates of influenza‐like illness in the outpatient setting. Influenza and Other Respiratory Viruses DOI: 10.1111/irv.12014.

Background:  Estimating influenza incidence in outpatient settings is challenging. We used outpatient healthcare practice populations as a proxy to estimate community incidence of influenza‐like illness (ILI) and laboratory‐confirmed influenza‐associated ILI.

Methods:  From October 2009 to July 2010, 38 outpatient practices in seven jurisdictions conducted surveillance for ILI (fever with cough or sore throat for patients ≥2 years; fever with ≥1 respiratory symptom for patients <2 years). From a sample of patients with ILI, respiratory specimens were tested for influenza.

Results:  During the week of peak influenza activity (October 24, 2009), 13% of outpatient visits were for ILI and influenza was detected in 72% of specimens. For the 10‐month surveillance period, ILI and influenza‐associated ILI incidence were 20·0 (95% CI: 19·7, 20·4) and 8·7/1000 (95% CI: 8·2, 9·2) persons, respectively. Influenza‐associated ILI incidence was highest among children aged 2–17 years. Observed trends were highly correlated with national ILI and virologic surveillance.

Conclusions:  This is the first multistate surveillance system demonstrating the feasibility of using outpatient practices to estimate the incidence of medically attended influenza at the community level. Surveillance demonstrated the substantial burden of pandemic influenza in outpatient settings and especially in children aged 2–17 years. Observed trends were consistent with established syndromic and virologic systems.

Seasonal maintenance of influenza vaccine-induced antibody response in kidney transplant recipients

BACKGROUND/AIMS

Although annual influenza vaccination is recommended for kidney transplant recipients, efficacy as reflected by serum antibody titers has not been well studied beyond 1 month in kidney transplant recipients.

METHODS

We performed a single-center prospective cohort study of 51 kidney transplant recipients and 102 healthy controls receiving the 2006-2007 influenza vaccine. Anti-hemagglutinin antibody titers to A/H1N1, A/H3N2, and B were measured before and 1 month after vaccination, and again at the end of influenza season. The primary outcome was the proportion of participants maintaining seroprotection (antibody titer ≥1:32) for the duration of the influenza season after influenza vaccination.

RESULTS

Median follow-up time was 175 and 155 days in the transplant and control groups, respectively. For types A/H1N1 and B, a similar high proportion of the transplant and control groups (88.5 and 81.6% vs. 83.7 and 74.2% for A/H1N1 and B, respectively) maintained seroprotection. For type A/H3N2, significantly less of the transplant group (66.7%) versus the control group (90%) maintained a protective influenza vaccine response (odds ratio 0.21, 95% confidence interval 0.07-0.64). This difference disappeared in adjusted analyses. Actual geometric mean titers decreased significantly within both groups (p < 0.001) but this did not differ between groups.

CONCLUSIONS

Once they have developed protective vaccine-induced antibody responses to influenza vaccine, kidney transplant recipients are able to maintain adequate protective levels of antibody compared with healthy controls.

The epidemiology of interpandemic and pandemic influenza in Vietnam, 2007-2010: the Ha Nam household cohort study I

Prospective community-based studies have provided fundamental insights into the epidemiology of influenza in temperate regions, but few comparable studies have been undertaken in the tropics. The authors conducted prospective influenza surveillance and intermittent seroprevalence surveys in a household-based cohort in Vietnam between December 2007 and April 2010, resulting in 1,793 person-seasons of influenza surveillance. Age- and sex-standardized estimates of the risk of acquiring any influenza infection per season in persons 5 years of age or older were 21.1% (95% confidence interval: 17.4, 24.7) in season 1, 26.4% (95% confidence interval: 22.6, 30.2) in season 2, and 17.0% (95% confidence interval: 13.6, 20.4) in season 3. Some individuals experienced multiple episodes of infection with different influenza types/subtypes in the same season (n = 27) or reinfection with the same subtype in different seasons (n = 22). The highest risk of influenza infection was in persons 5-9 years old, in whom the risk of influenza infection per season was 41.8%. Although the highest infection risk was in school-aged children, there were important heterogeneities in the age of infection by subtype and season. These heterogeneities could influence the impact of school closure and childhood vaccination on influenza transmission in tropical areas, such as Vietnam.

A hybrid EM and Monte Carlo EM algorithm and its application to analysis of transmission of infectious diseases

In epidemics of infectious diseases such as influenza, an individual may have one of four possible final states: prior immune, escaped from infection, infected with symptoms, and infected asymptomatically. The exact state is often not observed. In addition, the unobserved transmission times of asymptomatic infections further complicate analysis. Under the assumption of missing at random, data-augmentation techniques can be used to integrate out such uncertainties. We adapt an importance-sampling-based Monte Carlo Expectation-Maximization (MCEM) algorithm to the setting of an infectious disease transmitted in close contact groups. Assuming the independence between close contact groups, we propose a hybrid EM-MCEM algorithm that applies the MCEM or the traditional EM algorithms to each close contact group depending on the dimension of missing data in that group, and discuss the variance estimation for this practice. In addition, we propose a bootstrap approach to assess the total Monte Carlo error and factor that error into the variance estimation. The proposed methods are evaluated using simulation studies. We use the hybrid EM-MCEM algorithm to analyze two influenza epidemics in the late 1970s to assess the effects of age and preseason antibody levels on the transmissibility and pathogenicity of the viruses.

Successful use of volunteers to conduct school-located mass influenza vaccination clinics

OBJECTIVE

To determine the feasibility of using volunteers to assist in school-located mass vaccination clinics for influenza.

METHODS

A set of elementary school-based mass vaccination clinics was implemented in Carroll County, Maryland by the local health department in the 2005-2006 school year. In addition to using health department personnel, fiscal restraints necessitated using medical volunteers and lay volunteers to assist health professionals. The medical volunteers included physicians, nurses, and pharmacists, and were responsible for administering intranasal vaccine (live, attenuated influenza vaccine [LAIV]). We assessed the performance, as measured by the number of vaccinations administered, and effort expended by these volunteers.

RESULTS

A total of 5319 (44%) of the 12,090 elementary school children in the county received LAIV. Of the estimated 3547 (66%) children eligible and consenting to receive a second dose, 3124 (88%) received it. In total, 8806 doses of LAIV were administered. Health department nurses worked 42 person-days and were assisted by medical and allied health professionals volunteering 87 person-days without compensation, totaling 581 person-hours spent in this effort.

CONCLUSIONS

A mass school-located influenza vaccination program using medical and lay volunteers guided by health department nurses is feasible. Several issues were identified to improve future clinics and help make the program sustainable.

Pediatrician attitudes concerning school-located vaccination clinics for seasonal influenza

OBJECTIVE

Vaccinating all children aged 6 months to 18 years every year has potentially large ramifications for office-based primary care pediatricians. We determined the degree to which pediatricians support routine annual influenza vaccination outside the medical home, especially in school-located mass influenza vaccination clinics.

METHODS

Internet-based survey sent in May and June 2009 to all 623 currently practicing primary care general pediatricians who were members of the Maryland Chapter of the American Academy of Pediatrics.

RESULTS

Of those surveyed, 193 (31%) responded. Approximately 67% reported they vaccinated more than half the children in their practice with at least one dose in the 2008-2009 influenza season, and about half anticipated that, in their office, they would not attain ≥75% coverage of all patients older than 5 months of age. Approximately 27% of respondents predicted they would likely have difficulty obtaining sufficient vaccine to cover commercially insured patients, and 32% were likely to have difficulty getting sufficient vaccine to cover Medicaid, underinsured, and uninsured patients because of ordering or distribution problems. Approximately 78% of respondents cited borderline or poor reimbursement for influenza vaccinations, and 53% had unused vaccine at the end of the 2008-2009 influenza season. Ninety-six percent of respondents supported school-located influenza vaccination programs in their community for their patients.

CONCLUSIONS

These results indicate awareness by primary care pediatricians in Maryland of the potential difficulties involved in implementing universal influenza vaccinations in their practice and their support of school-located vaccination programs managed by the local health department in their community.

The population based socioeconomic burden of pediatric influenza-associated hospitalization in Hong Kong

We described the monetary and non-monetary cost incurred by children hospitalized for virologically confirmed influenza virus infection in a population-based prospective 3-year study. The mean direct and indirect cost of each child hospitalized was $1217.82 (95% CI, 1111.54-1324.23) and $1328.33 (95% CI, $1136.79-1520.00) for influenza A and B, respectively. School age patients took a mean (SD) of 4.70 (3.05) days and 5.31 (3.62) days of sick leave for influenza A and B infection, respectively. Pediatric influenza A and B hospitalization was associated with 662-1046 days of school absenteeism and 214-336 days of parental work loss per 10,000 population <18 years of age per year. We showed that the cost incurred by hospitalization alone, was comparable to the cost of annual universal pediatric influenza vaccination especially in children 6 months to under 6 years of age and vaccination would result in much larger cost-savings when non-monetary costs are included.

Pediatricians' attitudes about collaborations with other community vaccinators in the delivery of seasonal influenza vaccine

OBJECTIVE

Achieving universal influenza vaccination among children may necessitate collaborative delivery involving both practices and community vaccinators. We assessed among pediatricians nationally their preferences regarding location of influenza vaccination for patient subgroups and their attitudes about collaborative delivery methods.

METHODS

The design/setting was a national survey conducted from July 2009 to October 2009. Participants included a representative sample of pediatricians from the American Academy of Pediatrics.

RESULTS

The response rate was 79% (330 of 416). Physicians felt strongly that vaccination should occur in their practice for children with chronic conditions (52%) and healthy 6-24-month-old infants (48%), but few felt strongly about healthy 5-18-year-olds (17%). Most (78%) thought having multiple delivery sites increased vaccination rates, and 86% thought that influenza vaccine should be available at school. Physicians reported being very/somewhat willing to hold joint community clinics with public health entities (76%) and to suggest to patient subgroups that they receive vaccine at community sites, including public clinics or pharmacies (76%). The most frequently reported barriers to collaborative delivery with community sites or school-located delivery included concerns about the following: estimating the amount of vaccine to order if children are vaccinated elsewhere (community 56%; school 80%); transfer of vaccine records (community 57%; school 78%); and reluctance of families to go outside of the office (community 45%; school 74%).

CONCLUSIONS

Most physicians are in favor of school-located or collaborative influenza vaccine delivery with community vaccinators, especially for healthy school-aged children. Collaborative approaches will require planning to ensure transfer of records, effective targeting of subgroups, and provisions to protect providers from being left with extra influenza supply.

Direct and indirect impact of influenza vaccination of young children on school absenteeism

Special mass influenza vaccination programs of elementary school-aged children (ESAC) in some or all Maryland Counties were conducted during the falls of 2005-2007. From 3% to 46% of ESAC received live attenuated influenza vaccine during these county programs, which were in addition to routine influenza vaccination efforts conducted in county medical offices. Anonymous, all cause public school absentee data for all grades was available from 11 of Maryland's 24 counties. Binomial regression was used to estimate associations between the percentage of children vaccinated in each county and the degree of increase in absenteeism rates during influenza outbreaks. We estimated that, for every 20% increase in vaccination rates for ESAC during these special programs, a 4% decrease in the rise in absentee rates occurred during influenza outbreak periods in both elementary and upper schools (P<0.05). These results suggest both direct and indirect benefits of influenza vaccination of young children.

Rural parents' vaccination-related attitudes and intention to vaccinate middle and high school children against influenza following educational influenza vaccination intervention

OBJECTIVE

This study examined changes in parental influenza vaccination attitudes and intentions after participating in school-based educational influenza vaccination intervention.

METHODS

Participants were drawn from three counties participating in a school-based influenza vaccination intervention in rural Georgia (baseline N=324; follow-up N=327). Data were collected pre- and post-intervention from phone surveys with parents' with children attending middle- and high-school. Attitudes, beliefs, vaccination history, and intention to vaccinate were assessed.

RESULTS

Parents who participated in the intervention conditions reported significantly higher influenza vaccination rates in their adolescents, relative to a control group, as well as increased vaccination rates post-intervention participation relative to their baseline rates. Intervention participants reported greater intention to have their adolescent vaccinated in the coming year compared to control parents. Significant differences were observed post intervention in perceived barriers and benefits of vaccination.

CONCLUSIONS

These findings suggest that a school-delivered educational influenza vaccination intervention targeting parents and teens may influence influenza vaccination in rural communities. Future influenza vaccination efforts geared toward the parents of rural middle- and high-school students may benefit from addressing barriers and benefits of influenza vaccination.

Reduction in the incidence of influenza A but not influenza B associated with use of hand sanitizer and cough hygiene in schools: a randomized controlled trial

BACKGROUND

Laboratory-based evidence is lacking regarding the efficacy of nonpharmaceutical interventions (NPIs) such as alcohol-based hand sanitizer and respiratory hygiene to reduce the spread of influenza.

METHODS

The Pittsburgh Influenza Prevention Project was a cluster-randomized trial conducted in 10 elementary schools in Pittsburgh, PA, during the 2007 to 2008 influenza season. Children in 5 intervention schools received training in hand and respiratory hygiene, and were provided and encouraged to use hand sanitizer regularly. Children in 5 schools acted as controls. Children with influenza-like illness were tested for influenza A and B by reverse-transcriptase polymerase chain reaction.

RESULTS

A total of 3360 children participated in this study. Using reverse-transcriptase polymerase chain reaction, 54 cases of influenza A and 50 cases of influenza B were detected. We found no significant effect of the intervention on the primary study outcome of all laboratory-confirmed influenza cases (incidence rate ratio [IRR]: 0.81; 95% confidence interval [CI]: 0.54, 1.23). However, we did find statistically significant differences in protocol-specified ancillary outcomes. Children in intervention schools had significantly fewer laboratory-confirmed influenza A infections than children in control schools, with an adjusted IRR of 0.48 (95% CI: 0.26, 0.87). Total absent episodes were also significantly lower among the intervention group than among the control group; adjusted IRR 0.74 (95% CI: 0.56, 0.97).

CONCLUSIONS

NPIs (respiratory hygiene education and the regular use of hand sanitizer) did not reduce total laboratory-confirmed influenza. However, the interventions did reduce school total absence episodes by 26% and laboratory-confirmed influenza A infections by 52%. Our results suggest that NPIs can be an important adjunct to influenza vaccination programs to reduce the number of influenza A infections among children.

Incidence of influenza in healthy adults and healthcare workers: a systematic review and meta-analysis

Background

Working in healthcare is often considered a risk factor for influenza; however, this risk has not been quantified. We aimed to systematically review evidence describing the annual incidence of influenza among healthy adults and healthcare workers (HCWs).

Methods and Findings

We searched OVID MEDLINE (1950 to 2010), EMBASE (1947 to 2010) and reference lists of identified articles. Observational studies or randomized trials reporting full season or annual influenza infection rates for healthy, working age adult subjects and HCWs were included. Influenza infection was defined as a four-fold rise in antibody titer, or positive viral culture or polymerase chain reaction.

From 24,707 citations, 29 studies covering 97 influenza seasons with 58,245 study participants were included. Pooled influenza incidence rates (IR) (95% confidence intervals (CI)) per 100 HCWs per season and corresponding incidence rate ratios (IRR) (95% CI) as compared to healthy adults were as follows. All infections: IR 18.7 (95% CI, 15.8 to 22.1), IRR 3.4 (95% CI, 1.2 to 5.7) in unvaccinated HCWs; IR 6.5 (95% CI, 4.6 to 9.1), IRR 5.4 (95% CI, 2.8 to 8.0) in vaccinated HCWs. Symptomatic infections: IR 7.5 (95% CI, 4.9 to 11.7), IRR 1.5 (95% CI, 0.4 to 2.5) in unvaccinated HCWs, IR 4.8 (95% CI, 3.2 to 7.2), IRR 1.6 (95% CI, 0.5 to 2.7) in vaccinated HCWs.

Conclusions

Compared to adults working in non-healthcare settings, HCWs are at significantly higher risk of influenza.

The effect of age on transmission of 2009 pandemic influenza A (H1N1) in a camp and associated households

BACKGROUND

A major portion of influenza disease burden during the 2009 pandemic was observed among young people.

METHODS

We examined the effect of age on the transmission of influenza-like illness associated with the 2009 pandemic influenza A (H1N1) virus (pH1N1) for an April-May 2009 outbreak among youth-camp participants and household contacts in Washington State.

RESULTS

An influenza-like illness attack rate of 51% was found among 96 camp participants. We observed a cabin secondary attack rate of 42% (95% confidence interval = 21%-66%) and a camp local reproductive number of 2.7 (1.7-4.1) for influenza-like illness among children (less than 18 years old). Among the 136 contacts in the 41 households with an influenza-like illness index case who attended the camp, the influenza-like illness secondary attack rate was 11% for children (5%-21%) and 4% for adults (2%-8%). The odds ratio for influenza-like illness among children versus adults was 3.1 (1.3-7.3).

CONCLUSIONS

The strong age effect, combined with the low number of susceptible children per household (1.2), plausibly explains the lower-than-expected household secondary attack rate for influenza-like illness, illustrating the importance of other venues where children congregate for sustaining community transmission. Quantifying the effects of age on pH1N1 transmission is important for informing effective intervention strategies.

Description and evaluation of the 2009-2010 Pennsylvania Influenza Sentinel School Monitoring System

OBJECTIVES

We described and evaluated the 2009-2010 Pennsylvania Influenza Sentinel School Monitoring System, a voluntary sentinel network of schools that report data on school absenteeism and visits to the school nurse for influenza-like illness (ILI).

METHODS

Participating schools provided daily absenteeism and ILI data on a weekly basis through an online survey. We used participation and weekly response rates to determine acceptability, timeliness, and simplicity. We assessed representativeness by comparing participating schools with nonparticipating schools. We compared monitoring system data with statewide reports of laboratory-confirmed influenza.

RESULTS

Of the 3244 Pennsylvania public schools, 367 (11%) enrolled in the system. On average, 79% of enrolled schools completed the survey each week. Although the peak week of elevated absenteeism coincided with the peak of statewide laboratory-confirmed influenza cases, the correlation between absenteeism and state data was nonsignificant (correlation coefficient = 0.10; P = .56). Trends in ILI correlated significantly with state data (correlation coefficient = 0.67; P < .001).

CONCLUSIONS

The school-based sentinel system is a simple, acceptable, reliable device for tracking absenteeism and ILI in schools. Further analyses are necessary to determine the comparative value of this system and other influenza surveillance systems.

Reconstructing the 2003/2004 H3N2 influenza epidemic in Switzerland with a spatially explicit, individual-based model

world has not faced a severe pandemic for decades, except the rather mild H1N1 one in 2009, pandemic influenza models are inherently hypothetical and validation is, thus, difficult. We aim at reconstructing a recent seasonal influenza epidemic that occurred in Switzerland and deem this to be a promising validation strategy for models of influenza spread.

METHODS

We present a spatially explicit, individual-based simulation model of influenza spread. The simulation model bases upon (i) simulated human travel data, (ii) data on human contact patterns and (iii) empirical knowledge on the epidemiology of influenza. For model validation we compare the simulation outcomes with empirical knowledge regarding (i) the shape of the epidemic curve, overall infection rate and reproduction number, (ii) age-dependent infection rates and time of infection, (iii) spatial patterns.

RESULTS

The simulation model is capable of reproducing the shape of the 2003/2004 H3N2 epidemic curve of Switzerland and generates an overall infection rate (14.9 percent) and reproduction numbers (between 1.2 and 1.3), which are realistic for seasonal influenza epidemics. Age and spatial patterns observed in empirical data are also reflected by the model: Highest infection rates are in children between 5 and 14 and the disease spreads along the main transport axes from west to east.

CONCLUSIONS

We show that finding evidence for the validity of simulation models of influenza spread by challenging them with seasonal influenza outbreak data is possible and promising. Simulation models for pandemic spread gain more credibility if they are able to reproduce seasonal influenza outbreaks. For more robust modelling of seasonal influenza, serological data complementing sentinel information would be beneficial.