The determinants of 2009 pandemic A/H1N1 influenza vaccination: a systematic review

Background

Pandemic A/H1N1 influenza vaccine coverage varied widely across countries. To understand the factors influencing pandemic influenza vaccination and to guide the development of successful vaccination programs for future influenza pandemics, we identified and summarized studies examining the determinants of vaccination during the 2009 influenza pandemic.

Methods

We performed a systematic literature review using the PubMED electronic database from June 2009 to February 2011. We included studies examining an association between a possible predictive variable and actual receipt of the pandemic A/H1N1 influenza vaccine. We excluded studies examining intention or willingness to receive the vaccine.

Results

Twenty-seven studies were identified from twelve countries. Pandemic influenza vaccine coverage varied from 4.8% to 92%. Coverage varied by population sub-group, country, and assessment method used. Most studies used questionnaires to estimate vaccine coverage, however seven (26%) used a vaccination registry. Factors that positively influenced pandemic influenza vaccination were: male sex, younger age, higher education, being a doctor, being in a priority group for which vaccination was recommended, receiving a prior seasonal influenza vaccination, believing the vaccine to be safe and/or effective, and obtaining information from official medical sources.

Conclusions

Vaccine coverage during the pandemic varied widely across countries and population sub-groups. We identified some consistent determinants of this variation that can be targeted to increase vaccination during future influenza pandemics.     

Factors influencing pandemic influenza vaccination of healthcare workers--a systematic review

Introduction

Maintaining the health and availability of Health care workers (HCW) is an essential component of pandemic preparedness. A key to protecting HCW during the H1N1 pandemic was influenza vaccination. Numerous researchers have reported on factors influencing H1N1 vaccination behaviour in various HCW groups. This systematic review aims to inform future influenza vaccine interventions and pandemic planning processes via the examination of literature in HCW H1N1 vaccination, in order to identify factors that are (1) unique to pandemic influenza vaccination and (2) similar to seasonal influenza vaccination research.

Methods

We conducted a comprehensive review of literature (MEDLINE, PubMed, EMBASE, PsycINFO, CINHAL, AMED, Cochrane Library, ProQuest, and grey literature sources) published between January 2005 and December 2011 to identify studies relevant to HCW pH1N1 vaccine uptake/refusal.

Results

20 publications sampling HCW from different geographic regions are included in this review. H1N1 vaccine coverage was found to be variable (9–92%) across HCW populations, and self-reported vaccine status was the most frequently utilized predictor of pandemic vaccination. HCW were likely to accept the H1N1 vaccine if they perceived, (1) the H1N1 vaccine to be safe, (2) H1N1 vaccination to be effective in preventing infection to self and others (i.e. loved ones, co-workers and patients), and (3) H1N1 was a serious and severe infection. Positive cues to action, such as the access of scientific literature, trust in public health communications and messaging, and encouragement from loved ones, physicians and co-workers were also found to influence HCW H1N1 uptake. Previous seasonal influenza vaccination was found to be an important socio-demographic predictor of vaccine uptake. Factors unique to HCW pandemic vaccine behaviour are (1) lack of time and vaccine access related barriers to vaccination, (2) perceptions of novel and rapid pandemic vaccine formulation, and (3) the strong role of mass media on vaccine uptake.

Conclusions

Many of the factors that influenced HCW pandemic vaccination decisions have previously been reported in seasonal influenza vaccination literature, but some factors were unique to pandemic vaccination. Future influenza vaccine campaigns should emphasize the benefits of vaccination and highlight positive cues to vaccination, while addressing barriers to vaccine uptake in order to improve vaccine coverage among HCW populations. Since pandemic vaccination factors tend be similar among different HCW groups, successful pandemic vaccination strategies may be effective across numerous HCW populations in pandemic scenarios.     

Correlates of 2009 H1N1 influenza vaccination among day care-aged children, Miami-Dade County

Background

The aim of this study was to assess factors influencing 2009 H1N1 influenza vaccination among a demographically diverse group of day care-aged children. Day care children were chosen because they were an initial target group for vaccination and are at higher risk of influenza infection than children cared for at home.

Methods

A cross-sectional study was conducted from March to May 2010 among parents of day care aged children in 13 day care facilities in Miami-Dade County. Data was collected by an anonymous self-administered two-page 20 question survey which consisted of demographic variables and information regarding 2009 H1N1 influenza vaccine knowledge, attitude and acceptance. Data was analyzed using SAS to conduct both bivariate and multivariate analyses.

Results

There were 773 participants in the study. The response rate ranged from 42% to 72.2% among day care centers. A total of 172 parents (22.3%) and 225 (29.1%) children had received the 2009 H1N1 influenza vaccine. Non-Hispanic White and Black parents were more likely to vaccinate their children than Hispanic and Haitian parents. Primary reasons for non-vaccination included vaccine safety (36.7%) and side effects (27.1%). Among parents who spoke with a health care professional, 274 (61.4%) stated the health care professional recommended the vaccine.

Conclusion

Misperceptions about influenza vaccination among parents created a barrier to 2009 H1N1 influenza vaccination. Parents who got the vaccine, who believed the vaccine was safe and whose children had a chronic condition were more likely to immunize their children. Clear, reliable and consistent vaccine information to the public and health care providers and initiatives targeting minority groups may increase vaccination coverage among this population.     

Factors associated with uptake of seasonal and pandemic influenza vaccine among clinical risk groups in the UK: an analysis using the General Practice Research Database

Background

Influenza vaccine uptake rates are low compared with uptake rates of many other vaccines. It is unclear how this differs between risk groups in the population and between pandemic and non-pandemic influenza vaccines.

Aim

This study sought to estimate uptake rates of pandemic and seasonal influenza vaccines among clinical risk groups in the UK during the 2009/2010 influenza season and to identify predictors of vaccine uptake in this cohort.

Methods

Uptake rates were calculated using data from the UK General Practice Research Database (GPRD). Predictors of vaccination were identified using a modified Poisson regression with robust standard error estimates.

Results

Uptake of pandemic influenza vaccine in clinical risk groups was 40.3% and uptake of seasonal influenza vaccine was 61.3%. Factors found to be predictive of seasonal and pandemic influenza vaccination included age and the total number of underlying health conditions an individual had. At risk individuals in those age groups in which universal vaccination of the general population was recommended were more likely to have been vaccinated than individuals in age groups in which only clinical risk groups were recommended for vaccination; hence children in clinical risk groups were more likely to receive pandemic than seasonal influenza vaccine. In older people, having a history of Guillain Barré syndrome was associated with a reduced likelihood of receipt of both seasonal (IRR_adj 0.83, CI₉₅ 0.77–0.90) and pandemic influenza vaccines (IRR_adj 0.82, CI₉₅ 0.73–0.92).

Discussion

Uptake of pandemic influenza vaccine was lower than that of seasonal influenza vaccine among those at a clinically high risk of influenza related morbidity. This suggests that vaccination strategies may need to be altered during future pandemics. Recommending universal vaccination within age categories in which there is a large proportion of high risk individuals could be considered as this may result in higher uptake among clinical risk groups.     

Acceptability of pandemic A(H1N1) influenza vaccination by Essential Community Workers in 2010 Alicante (Spain), perceived seriousness and sources of information

Objective

Describe acceptability of pandemic A(H1N1) influenza vaccination by Essential Community Workers (ECWs) from Alicante province (Spain) in January 2010. Evaluate the correlation with attitudes, beliefs, professional advice and information broadcasted by media.

Method

In this cross-sectional study, face-to-face interviews were conducted with 742 ECWs to assess their attitudes towards vaccination against the pandemic influenza strain. A multivariable regression model was made to adjust the Odds Ratios (ORs).

Results

Some ECWs reported having been vaccinated with seasonal vaccine, 21.5% (95%IC 18.6–24.9); only 15.4% (95%IC 12.8–18.4) with the pandemic one. ECWs vaccinated regularly against seasonal flu (OR 5.1; 95%IC 2.9–9.1), those who considered pandemic influenza as a severe or more serious disease than seasonal flu (OR 3.8; 95%IC 2.1–6.7) and those who never had doubts about vaccine safety (OR 3.7; 95%IC2.1–6.7) had a better acceptance of pandemic vaccine. Finally, 78.7% (95%IC 75.1–81.4) had doubts about pandemic vaccine's effectiveness.

Conclusion

The vast amount of information provided by the media did not seem to be decisive to prevent doubts or to improve the acceptability of the vaccine in ECWs. Professional advice should be the focus of interest in future influenza vaccination campaigns. These results should be taken into account by health authorities.     

Predictors of IV behaviors during and after the 2009 influenza pandemic in France

Background

Controversies about the 2009 H1N1 pandemic influenza vaccination might have impacted the motivational processes that underlie individual immunization against seasonal influenza. The purpose of this article is to investigate correlates of vaccine uptake during and after the pandemic.

Methods

Data from the 1174 subjects of the CoPanFlu France cohort aged 15 and over were used. We used logistic regression models to identify social and behavioral predictors of getting vaccinated against seasonal influenza in 2009–2010 and in 2010–2011 and against H1N1 influenza in 2009–2010.

Results

This study points out that correlates of vaccination behaviors varied according to the vaccine. Respondents under 65 years who adopted the seasonal influenza vaccine were, as usual, more likely to belong to a target group and have a lower education, contrary to subjects who chose the pandemic vaccine. Exceptionally during the pandemic, a higher socioeconomic status also led to adoption of either vaccine. Motivational processes differed by vaccine. Uptaking the “new” pandemic vaccine was the result of a deliberative decision-making process, influenced by cognitive factors related to the pandemic context (such as perceived severity of the H1N1 flu strain and trust in public health authorities). In contrast, respondents got the seasonal flu vaccine without relying on explicit justifications, but instead through habit of performing this behavior in the past.

Conclusions

Target groups for seasonal influenza but not those for pandemic influenza were more likely to adopt the pandemic vaccine, which is a cause for great concern. This may be due to large extent to the automatic and habitual nature of influenza vaccination decisions. Public health authorities, should pay more attention to situational than informational cues to facilitate vaccine uptake among priority groups, especially in case of mild pandemic influenza.     

Determinants of uptake of influenza vaccination among pregnant women – A systematic review

Background

Pregnant women have the highest priority for seasonal influenza vaccine. However, suboptimal coverage has been repeatedly noted in this population. To improve vaccine uptake, reviewing the determinants of vaccination is of increasing importance.

Methods

A detailed literature search was performed up to November 30, 2013 to retrieve articles related to uptake of influenza vaccination during pregnancy.

Results

Forty-five research papers were included in the review. Twenty-one studies assessed the coverage of seasonal influenza vaccination, 13 studies assessed coverage of A/H1N1 pandemic vaccination and 11 studies assessed both. Vaccination uptake ranged from 1.7% to 88.4% for seasonal influenza, and from 6.2% to 85.7% for A/H1N1 pandemic influenza. Many pregnant women were unaware that they were at high risk for influenza and its complications during pregnancy. They were also more likely to underestimate the threat of influenza to themselves and their fetus. Moreover, they had substantial concerns about the safety and efficacy of the influenza vaccine during pregnancy. Negative media reports contributed to the perception that influenza vaccination during pregnancy was risky and could result in adverse pregnancy outcomes. Although health care providers’ (HCPs) recommendations were consistently associated with vaccine uptake, most did not recommend the vaccine to their pregnant clients.

Conclusions

Influenza vaccination uptake among pregnant women is suboptimal and HCPs rarely recommend it. Positive vaccination recommendations from HCPs as well as direct access to the vaccine would likely substantially improve vaccination acceptance.     

The impact of pandemic A(H1N1)pdm09 influenza and vaccine-associated adverse events on parental attitudes and influenza vaccine uptake in young children

Introduction

Parental attitudes towards vaccination significantly influence vaccine uptake. The A(H1N1)pdm09 influenza pandemic was followed in 2010 by an unprecedented increase in febrile reactions in children receiving trivalent inactivated influenza vaccine manufactured by bioCSL. Uptake of TIV in children <5 years in Western Australia (WA) decreased in 2010 and has remained low. The impact of pandemic A(H1N1)pdm09 and adverse-events on parental attitudes towards vaccination is uncertain.

Materials and Methods

A parental attitudes survey towards influenza illness and vaccination was conducted as part of the West Australian Influenza Vaccine Effectiveness study. Vaccination status was assessed by parental interview and confirmed by the national register and/or vaccine providers. Parental attitudes from vaccinated and unvaccinated children and attitudes in 2008–2009 and 2010–2012 were compared. Principal Component Analysis was conducted to determine core attitudes that influenced vaccine uptake.

Results

Vaccination history and parental attitude surveys were available from 2576 children. Parents of fully vaccinated children less frequently stated that influenza was a mild disease, more frequently stated that influenza vaccine was safe and were less frequently worried about vaccine side effects.Uptake of influenza vaccine decreased significantly from 2010 onwards. From 2010, parents were less concerned about severe influenza, but more concerned about vaccine side effects and safety. Despite this significant shift in attitudes towards influenza vaccine, parental acceptance of vaccines on the national immunisation program did not change. Principal Component Analysis revealed that attitudes around vaccine safety and efficacy were the most important attitudes impacting on vaccine uptake.

Conclusions

Parental attitudes to influenza vaccine changed from 2010. Confidence in the WA preschool influenza vaccination program remains low yet appeared unchanged for other vaccines. Restoring public confidence in childhood influenza vaccination is needed before uptake can be improved.     

What lies behind the low rates of vaccinations among nurses who treat infants?

Background

In most countries rates of immunizations of health care workers with recommended vaccines are not satisfactory.

Objectives

To identify reasons behind the low rates of compliance of Israeli nurses in Mother and Child Healthcare Centers (MCHC) with an official request for pertussis vaccination.

Methods

Three focus groups were conducted. Qualitative analysis identified themes that could explain the nurses’ non-compliance.

Results

Trust in health authorities was low, mainly following the A/H1N1 purported influenza pandemic. In addition, nurses did not see the importance of being role models for the public and demanded the autonomy to decide whether to receive vaccinations. The nurses differentiated between their role as nurses and their personal life, expressed fear of new vaccines and exhibited low levels of risk perception. Misconceptions regarding vaccinations were expressed by the nurses.

Conclusions

Antivaccinationist ideas were expressed by MCHC nurses and these attitudes may have led to non-compliance with vaccination guidelines.     

Acceptance of vaccination during pregnancy: experience with 2009 influenza A (H1N1) in the Netherlands

Objectives

In 2009, the Dutch government advised pregnant women to get vaccinated against influenza A (H1N1). A study was set up to gain insight into vaccination coverage and reasons why pregnant women seek vaccination or not.

Methods

We invited 14,529 pregnant women to complete an internet survey on vaccination during pregnancy in general and against 2009 influenza A (H1N1). Differences in background characteristics between unvaccinated and vaccinated women were investigated. Prediction analyses were carried out to determine which survey statement had the greatest impact on vaccination status or intention to get vaccinated during pregnancy.

Results

Of the 2993 included respondents, 63% reported to be vaccinated against 2009 influenza A (H1N1). Vaccination coverage was higher among older birth cohorts, women who had been pregnant before, women with underlying medical conditions, and women who reported no defined ‘life philosophy’. Protection of the child (after birth), the government's advice and possible harmful effects of the vaccine for the unborn child had the greatest predictive value for vaccination status. With regards vaccination during future pregnancies, 39% had a positive intention to obtain vaccination and 45% were neutral. The government's advice was the strongest predictor for intention. Furthermore, women expressed concern over lack of sufficient knowledge about vaccine safety.

Conclusions

A considerable number of pregnant women in the Netherlands reported to be vaccinated against 2009 influenza A (H1N1). The challenge for the government in the future will be to provide pregnant women and health care professionals with sufficient and clear information about disease severity and the benefits and safety of vaccination.     

Inactivated trivalent seasonal influenza vaccine induces limited cross-reactive neutralizing antibody responses against 2009 pandemic and 1934 PR8 H1N1 strains

Background

In June 2009, we conducted a prospective study in Singapore on 51 individuals to determine their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal influenza vaccine.

Materials and methods

Paired serum samples were obtained before and 3–4 weeks after vaccination. Virus microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine, pandemic H1N1-2009 and A/Puerto Rico/08/34 H1N1 strains.

Results

Post-vaccination, 43%, 12% and 24% of subjects displayed a 4-fold or greater rise in neutralizing antibody titers against the three strains, respectively. There was a positive correlation among individuals who showed increased titers to both pandemic H1N1-2009 and A/Puerto Rico/08/34 (p < 0.001). However, this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation and accessibility of predicted B-cell epitopes may explain the limited cross-reactivity of the antibodies directed against common H1N1 epitopes.

Conclusions

These results suggest that seasonal influenza vaccination confers a certain degree of cross-protection to other H1N1 strains. The correlation in cross-reactive antibody titers to A/Puerto Rico/08/34 and pandemic H1N1-2009 implies that previous exposure to pre-1957 H1N1 strains may confer some protection against the 2009 pandemic strain.     

Nurses' vaccination against pandemic H1N1 influenza and their knowledge and other factors

This study aimed to estimate the vaccination coverage against the pandemic H1N1 influenza in a group of nurses and determine the factors associated with their vaccination behaviours. An anonymous, self-administered questionnaire was distributed to a convenience sample of nurses who were enrolled on continuing professional education courses in a university in London. The survey response rate was 77.7% (n=522). A total of 172 (35.2%) nurses reported receiving the pandemic H1N1 vaccine in the 2009-2010 influenza season and only 22.3% of them had the intent to accept the vaccine in the next season. Compared to nurses with low knowledge scores, those with high knowledge scores were more likely to receive the pandemic H1N1 vaccine (p=0.017), recommend the vaccine to their patients (p=0.003), and have the willingness to recommend vaccination to patients in the future (p=0.009). There was a higher vaccination rate among nurses with higher risk perception scores than with lower scores (p=0.001). A small, positive correlation between H1N1 knowledge and risk perception scores was identified (p<0.001) indicating that a high knowledge level was associated with high levels of risk perception. More male nurses received the H1N1 vaccine than females (p<0.001) and there were a significant differences in the uptake among nurses from different clinical specialty groups (p<0.001). About half of the vaccinated nurses reported the intent to be vaccinated again but only 8.1% of the unvaccinated nurses had the intent to receive the vaccine in the next season (p<0.001). The pandemic H1N1 2009 influenza vaccination coverage among this nurse sample was sub-optional. Lack of knowledge and risk perception were predictors associated with the nurses' vaccination behaviours. The identified knowledge items should be addressed in future vaccination campaigns. The hindrances associated with continuing vaccination decision-making and factors contributing to the different vaccination coverage among clinical specialty groups require further exploration.     

Pre-vaccination immunity and immune responses to a cell culture-derived whole-virus H1N1 vaccine are similar to a seasonal influenza vaccine

Background

Immune responses to novel pandemic influenza vaccines may be influenced by previous exposure to antigenically similar seasonal strains.

Methods

An open-label, randomized, phase I/II study was conducted to assess the immunogenicity and safety of a non-adjuvanted, inactivated whole-virus H1N1 A/California/07/2009 vaccine. 408 subjects were stratified by age (18–59 and >60 years) and randomized 1:1 to receive two vaccinations with either 3.75 or 7.5 μg hemagglutinin antigen 21 days apart. Safety, immunogenicity and the influence of seasonal influenza vaccination and antibody cross-reactivity with a seasonal H1N1 strain was assessed.

Results

A single vaccination with either dose induced substantial increases in H1N1 A/California/07/2009 hemagglutination inhibition (HI) and neutralizing (MN) antibody titers in both adult and elderly subjects. A single 7.5 μg dose induced seroprotection rates of 86.9% in adults and 75.2% in elderly subjects. Two 7.5 μg vaccinations induced seroprotection rates in adult and elderly subjects of 90.9% and 89.1%, respectively. The robust immune response to vaccination was confirmed by analyses of neutralizing antibody titers. Both HI and MN antibodies persisted for ≥6 months post-vaccination. Between 34% and 49% of subjects had seroprotective levels of H1N1 A/California/07/2009 antibodies at baseline. Higher baseline HI titers were associated with receipt of the 2008–09 or 2009–10 seasonal influenza vaccine. High baseline A/California/07/2009 neutralizing antibody titers were also associated with high baseline titers against A/New Caledonia/20/99, a seasonal H1N1 strain which circulated and was included in the seasonal vaccine from 2000–01 to 2006–07. Pre-adsorption with A/H1N1/New Caledonia/20/99 antigen reduced A/H1N1/California/07/2009 baseline titers in 55% of tested sera. The vaccine was well tolerated with low rates of fever.

Conclusions

A whole-virus H1N1 A/California/07/2009 vaccine was safe and well tolerated and a single dose induced substantial immune responses similar to seasonal influenza vaccines, probably due to immunological priming by previous seasonal influenza vaccines or infections.     

Immune response after one or two doses of pandemic influenza A (H1N1) monovalent,AS03-adjuvanted vaccine in HIV infected adults

Introduction

Continued research is needed to evaluate and improve the immunogenicity of influenza vaccines in HIV infected patients. We aimed to determine the antibody responses after one or two doses of the AS03-adjuvanted pandemic influenza A (H1N1) vaccine in HIV infected patients.

Method

Following the influenza season 2009/2010, 219 HIV infected patients were included and divided into three groups depending on whether they received none (n = 60), one (n = 31) or two (n = 128) doses of pandemic influenza A (H1N1) vaccine. At inclusion, antibody titers for all patients were analyzed and compared to pre-pandemic antibody titers analyzed from serum samples in a local storage facility.

Results

4–9 months after a single immunization, we found a seroprotection rate of 77.4% and seroconversion rate of 67.7%. After two immunizations the rates increased significantly to seroprotection rate of 97.7% and seroconversion rate of 86.7%.

Conclusion

A single dose of AS03-adjuvanted pandemic influenza A (H1N1) vaccine created an adequate immune response in HIV infected patients lasting as long as 4–9 months. Two doses improved the immunogenicity further.     

Qualitative evaluation of Rhode Island's healthcare worker influenza vaccination regulations

Objective

To evaluate Rhode Island's revised vaccination regulations requiring healthcare workers (HCWs) to receive annual influenza vaccination or wear a mask during patient care when influenza is widespread.

Design

Semi-structured telephone interviews conducted in a random sample of healthcare facilities.

Setting

Rhode Island healthcare facilities covered by the HCW regulations, including hospitals, nursing homes, community health centers, nursing service agencies, and home nursing care providers.Participants Staff responsible for collecting and/or reporting facility-level HCW influenza vaccination data to comply with Rhode Island HCW regulations.

Methods

Interviews were transcribed and individually coded by interviewers to identify themes; consensus on coding differences was reached through discussion. Common themes and illustrative quotes are presented.

Results

Many facilities perceived the revised regulations as extending their existing influenza vaccination policies and practices. Despite variations in implementation, nearly all facilities implemented policies that complied with the minimum requirements of the regulations. The primary barrier to implementing the HCW regulations was enforcement of masking among unvaccinated HCWs, which required timely tracking of vaccination status and additional time and effort by supervisors. Factors facilitating implementation included early and regular communication from the state health department and facilities’ ability to adapt existing influenza vaccination programs to incorporate provisions of the revised regulations.

Conclusions

Overall, facilities successfully implemented the revised HCW regulations during the 2012–2013 influenza season. Continued maintenance of the regulations is likely to reduce transmission of influenza and resulting morbidity and mortality in Rhode Island's healthcare facilities.     

Failure of the vaccination campaign against A(H1N1) influenza in pregnant women in France: Results from a national survey

Background and objective

Pregnant women were a priority group for vaccination during the 2009 A(H1N1) influenza pandemic. In France, vaccination was organized in ad hoc centers. Women received vouchers by mail and were given a non-adjuvanted vaccine. Our objective was to assess the national vaccination rate among pregnant women and to determine the association of vaccination with maternal characteristics, prenatal care, and pregnancy-related health behaviors.

Method

Data came from a national representative sample of women who gave birth in March 2010 (N = 13 453) and were interviewed in the hospital before discharge; they were in the second trimester of pregnancy during the vaccination campaign. Associations between vaccination and socio-demographic and medical characteristics, region of residence, care providers, and preventive behaviors were assessed with bivariable analyses and logistic regression models.

Results

Vaccine coverage was 29.3% (95% CI: 28.6–30.1). The main reason for not being vaccinated was that women did not want this immunization (91%). In adjusted analyses, vaccination was more frequent in women who were older, employed, born in France, with a parity of 1 or 2 and specific favourable health behaviors. The adjusted odds ratio for women with a postgraduate educational level was 4.1 (95% CI: 3.5–4.8) compared to those who did not complete high school. Women with additional risk factors for complications from A(H1N1) infection had a vaccination rate similar to that of other women.

Conclusion

The vaccination campaign resulted in poor vaccination coverage, strong social inequalities, and no special protection for pregnant women at the highest risk of complications. These findings provide essential information for the organization of future vaccination campaigns.     

External cues to action and influenza vaccination among post-graduate trainee physicians in Toronto,Canada

Background

Understanding factors affecting trainee physician choices about vaccination may permit the design of more effective vaccination programmes.

Methods

To identify factors associated with seasonal and pandemic influenza vaccination, an online questionnaire based on the health belief model was sent to trainee physicians registered at the post-graduate medical education office at the University of Toronto in September 2011.

Results

963 complete responses were received from 1884 trainee physicians (51%); 28 (2.9%) reported an allergy to vaccine components and were excluded from further analysis. Reported seasonal influenza vaccination rates in 2008, 2009 and 2010 were 69% (648/935), 75% (708/935) and 76% (703/935), respectively; 788 (84%) reported receiving the A(H1N1)pdm09 vaccine. In multivariable analysis, number of years of post-graduate training (OR for 4+ versus 1–3 post-graduate years 2.2 (95% CL 1.3, 3.8)) was associated with receipt of the 2009 pandemic vaccine, as were four components of the health belief model: odds ratios were 4.7 (95% CL 3.0, 7.5) for perceived severity, 1.9 (95% CL 1.2, 2.9) for perceived benefits, .35 (95% CL .21, .59) for perceived barriers, and 5.8 (95% CLI 3.6, 9.1) for external cues to action. Both vaccinated and unvaccinated respondents reported that their decisions were significantly influenced by encouragement from their colleagues, families and employers.

Conclusion

Self-reported vaccination coverage among trainee physicians was high. External cues to action appear to be particularly important in trainee physician vaccination decisions: active institutional promotion may increase influenza vaccination rates in trainees.     

Comparable humoral response after two doses of adjuvanted influenza A/H1N1pdm2009 vaccine or natural infection in allogeneic stem cell transplant recipients

Background

The present study evaluated immunogenicity and tolerance of two-dose influenza A/H1N1pdm09 vaccination in allogeneic hematopoietic stem cell transplantation (HSCT) recipients, and compared the vaccine-induced humoral response to that triggered by natural infection in another group of HSCT patients.

Methods

Adult allogeneic HSCT recipients vaccinated with two doses of influenza A/H1N1pdm09 vaccine, separated by 3 weeks, and patients with proven influenza A/H1N1pdm09 infection were included. Antibody responses were measured by hemagglutination-inhibition assay 1) on days 0, 21, 42 and 6 months after the first vaccine injection in vaccinated patients and 2) before pandemic and after influenza A/H1N1pdm09 infection, in patients presented natural infection.

Results

At baseline, 3% of 59 recipients of adjuvanted vaccine and 0% of 20 infected patients were seroprotected (antibody titer ≥ 1/40). Seroprotection rate observed 42 days after vaccination was not different from that observed after natural infection (66% and 60% respectively, p = 0.78). In vaccinated patients, seroprotection rate increased significantly from 54% to 66% between day 21 and 42 (p = 0.015). Moreover, after 6 months, seroprotection rate in 21 vaccinated patients was similar to that observed in 10 infected patients evaluated at least 76 days after infection (D76–217) (60% and 81% respectively, p = 0.2). In multivariate analysis, no immunosuppressive treatment or chronic graft-versus-host disease (GVHD) and longer time between transplantation and vaccination/infection were associated with a stronger humoral response. The adjuvanted vaccine was safe with low rate of GVHD worsening.

Conclusion

In HSCT recipients, two doses of influenza A/H1N1pdm09 adjuvanted vaccine were safe and induced a humoral response comparable to that triggered by natural infection in these patients.     

Seasonal influenza vaccination predicts pandemic H1N1 vaccination uptake among healthcare workers in three countries

The aim of this study was to identify the common barriers and facilitators for acceptance of pandemic influenza vaccination across different countries. This study utilized a standardized, anonymous, self-completed questionnaire-based survey recording the demographics and professional practice, previous experience and perceived risk and severity of influenza, infection control practices, information of H1N1 vaccination, acceptance of the H1N1 vaccination and reasons of their choices and opinions on mandatory vaccination. Hospital-based doctors, nurses and allied healthcare workers in Hong Kong (HK), Singapore (SG) and Leicester, United Kingdom (UK) were recruited. A total of 6318 (HK: 5743, SG: 300, UK: 275) questionnaires were distributed, with response rates of 27.1% (HK), 94.7% (SG) and 94.5% (UK). The uptake rates for monovalent 2009 pandemic H1N1 vaccine were 13.5% (HK), 36.2% (SG) and 41.3% (UK). The single common factor associated with vaccine acceptance across all sites was having seasonal influenza vaccination in 2009. In UK and HK, overestimation of side effect reduced vaccination acceptance; and fear of side effect was a significant barrier in all sites. In HK, healthcare workers with more patient contact were more reluctant to accept vaccination. Drivers for vaccination in UK and HK were concern about catching the infection and following advice from health authority. Only a small proportion of respondents agreed with mandatory pandemic influenza vaccination (HK: 25% and UK: 42%), except in Singapore where 75.3% were in agreement. Few respondents (<5%) chose scientific publications as their primary source of information, but this group was more likely to receive vaccination.The acceptance of pandemic vaccine among healthcare workers was poor (13-41% of respondents). Breaking barriers to accept seasonal influenza vaccination should be part of the influenza pandemic preparedness plan. Mandatory vaccination even during pandemic is likely to arouse substantial discontent.     

A randomised, single-blind, dose-range study to assess the immunogenicity and safety of a cell-culture-derived A/H1N1 influenza vaccine in adult and elderly populations

Background

Modern cell-culture production techniques and the use of adjuvants helps to ensure that the global demand for pandemic influenza vaccine can be met. This study aimed to assess the immunogenicty and safety profiles of various cell-culture-derived A/H1N1 pandemic vaccine formulations in healthy adult and elderly subjects.

Methods

Adult (18–60 years) subjects (n = 544) received vaccine either containing 3.75 μg of antigen with half the standard dose of MF59^® (Novartis Vaccines and Diagnostics) adjuvant, 7.5 μg antigen with a full dose of MF59, or a non-adjuvanted vaccine containing 15 μg of antigen. Elderly (≥61 years) subjects (n = 268) received either the 3.75 μg or 7.5 μg adjuvanted formulations. Two priming vaccine doses were administered 3 weeks apart, followed by a single booster dose of seasonal influenza vaccine 1 year later. Immunogenicity was assessed 3 weeks after each vaccination. The safety profile of each formulation was evaluated throughout the study.

Results

A single primary dose of each A/H1N1 vaccine formulation was sufficient to meet all three European (CHMP) licensure criteria for pandemic influenza vaccines in adult subjects. Two licensure criteria were met after one vaccine dose in elderly subjects; two primary doses were required to meet all three criteria in this age group. The highest antibody titres were observed in response to the 7.5 μg vaccine containing a full dose of MF59 adjuvant. All subjects rapidly generated seroprotective antibody titres in response to booster vaccination.

Conclusion

This study identified one 3.75 μg vaccine dose containing half the standard dose of MF59 adjuvant as optimal for adults, two doses were optimal for elderly subjects. The antigen-sparing properties of MF59, and rapid, modern, cell-culture production techniques represent significant steps towards meeting the global demand for influenza vaccine.