Bruno Christian Ciancio

Estimates of Pandemic Influenza Vaccine Effectiveness in Europe, 2009–2010: Results of Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) Multicentre Case-Control Study

Results from a European multicentre case-control study reported by Marta Valenciano and colleagues suggest good protection by the pandemic monovalent H1N1 vaccine against pH1N1 and no effect of the 2009–2010 seasonal influenza vaccine on H1N1.

Study designs for timely estimation of influenza vaccine effectiveness using European sentinel practitioner networks.

European sentinel practitioner influenza surveillance networks represent a simple and feasible framework to conduct observational studies providing rapid and repeated influenza vaccine effectiveness estimates. The minimum requirements for those studies should be to correctly ascertain vaccination status, to include laboratory-confirmed influenza as outcome and to collect variables to control for confounding. Various study designs are possible including the screening method, computerised cohort and case control studies using various control groups. Selecting the study design is a compromise between methodological constraints, availability and ease of access to data sources and resources available. Results from practitioner-based studies complement other pieces of evidence (e.g. immunogenicity studies, vaccine efficacy, surveillance data) to assess the effect of influenza vaccination in the population.

I-MOVE Multi-Centre Case Control Study 2010-11: Overall and Stratified Estimates of Influenza Vaccine Effectiveness in Europe

Background In the third season of I-MOVE (Influenza Monitoring Vaccine Effectiveness in Europe), we undertook a multicentre case-control study based on sentinel practitioner surveillance networks in eight European Union (EU) member states to estimate 2010/11 influenza vaccine effectiveness (VE) against medically-attended influenza-like illness (ILI) laboratory-confirmed as influenza. Methods Using systematic sampling, practitioners swabbed ILI/ARI patients within seven days of symptom onset. We compared influenza-positive to influenza laboratory-negative patients among those meeting the EU ILI case definition. A valid vaccination corresponded to > 14 days between receiving a dose of vaccine and symptom onset. We used multiple imputation with chained equations to estimate missing values. Using logistic regression with study as fixed effect we calculated influenza VE adjusting for potential confounders. We estimated influenza VE overall, by influenza type, age group and among the target group for vaccination. Results We included 2019 cases and 2391 controls in the analysis. Adjusted VE was 52% (95% CI 30-67) overall (N = 4410), 55% (95% CI 29-72) against A(H1N1) and 50% (95% CI 14-71) against influenza B. Adjusted VE against all influenza subtypes was 66% (95% CI 15-86), 41% (95% CI -3-66) and 60% (95% CI 17-81) among those aged 0-14, 15-59 and ≥60 respectively. Among target groups for vaccination (N = 1004), VE was 56% (95% CI 34-71) overall, 59% (95% CI 32-75) against A(H1N1) and 63% (95% CI 31-81) against influenza B. Conclusions Results suggest moderate protection from 2010-11 trivalent influenza vaccines against medically-attended ILI laboratory-confirmed as influenza across Europe. Adjusted and stratified influenza VE estimates are possible with the large sample size of this multi-centre case-control. I-MOVE shows how a network can provide precise summary VE measures across Europe.

The importance of influenza prevention for public health

Annual epidemics of seasonal (inter-pandemic) influenza represent a significant burden on society in terms of morbidity, mortality, hospitalizations and lost working time. The impact of influenza depends on a mix of direct and indirect effects and is not easy to assess. Nevertheless there is a consensus in considering influenza prevention and mitigation high priorities for public health. We review the available evidence to assess the impact of influenza prevention focusing especially on vaccines and immunization strategies.

Monitoring and assessing vaccine safety: a European perspective

The success of vaccination programs is an uncontroversial reality – in Europe as well as worldwide. On the other hand, the perceived risk of adverse events in the general public is the most important threat for implementing successful vaccination programs in Europe. For this reason, monitoring and assessing vaccine safety is a priority for public health. Vaccine safety is assessed both before and after vaccine authorization. In postmarketing settings, different activities related to vaccine safety usually involve several different stakeholders. In 2005, a new EU agency, the European Centre for Disease Prevention and Control, was established with the aim to strengthen Europe’s defences against infectious diseases. Implementing stable links between different stakeholders and defining clear roles in the EU is paramount in order to provide optimal and transparent information on adverse reactions following immunization, with the final goal of increasing compliance to safe and effective vaccination programs.

Costs and benefits of influenza vaccination: more evidence, same challenges

Seasonal influenza vaccination coverage in most EU/EEA remains suboptimal. Providers’ and users’ confidence in influenza vaccines is undermined by reports of moderate to low vaccine effectiveness and by the lack of solid evidence on disease burden. A study from Preaud and co. indicates that even with current levels of vaccine effectiveness, increasing vaccination coverage would significantly reduce disease burden and health cost. The results of the study should be interpreted cautiously because some of the assumptions are not generalizable or are imprecise, especially those on vaccine coverage, disease burden and health cost. Increasing vaccination coverage in EU/EEA countries is very challenging. Multifaceted approaches and country specific strategies are needed to address vaccine hesitancy in health care workers and in the population, and to manage organisational and financial obstacles. One key element for increasing vaccination coverage is the development of better influenza vaccines, e.g. vaccines that are more effective, provide longer lasting immunity and do not require annual administration. Vaccine producers should consider this as the highest research priority in the field of influenza vaccine development.

Neuraminidase inhibitors in pandemic A/H1N1 flu

Jefferson and colleagues describe the effectiveness of neuraminidase inhibitors in otherwise healthy adults infected with seasonal flu virus,1 but it is mainly the A/H1N1 flu virus that is currently in circulation. Given the limited availability of vaccine against 2009 pandemic A/H1N1 flu, antiviral drugs have assumed a prominent role in reducing severe flu …