Extending recommendations for respiratory vaccines : experimental and non-experimental studies

Abstract

Context: * Many European countries are considering to extend recommendations for influenza vaccination to include otherwise healthy persons aged <65 years. However information about the potential impact of such extension is scarce, particularly for adults. Furthermore, the development of vaccines against RSV has progressed, and therefore insight into the RSV-associated burden is required. * Especially young children suffer from recurrent respiratory tract infections (RTI), with influenza viruses and Streptococcus pneumoniae as frequent pathogens. Evaluation of influenza vaccination with or without pneumococcal conjugate vaccination is therefore needed. Objectives: * To estimate the influenza- and RSV-associated mortality, hospitalisations and primary care burden in order to support national vaccination policies. * To evaluate the effects of influenza vaccination with or without pneumococcal conjugate vaccination on RTI in preschool children. Methods: * Using data from death registries, hospital admissions, primary care consultations, and virus surveillance during 1997-2003 in the Netherlands, the annual average influenza- and RSV-associated excesses of mortality, hospitalisations, and primary care consultations were estimated using rate difference methods. * The effects of influenza vaccination with or without pneumococcal conjugate vaccination were assessed in a randomised double-blind controlled trial among 579 children aged 18-72 months with a prior history of physician-diagnosed RTI (the ‘PRIMAKid’-trial). Results and conclusions: * In young children the highest influenza-associated excesses of hospitalisations and primary visits were observed. However, information about the effects of influenza vaccination among young children is lacking and further research should first address this prior to consideration to include this group in the recommendations for influenza vaccinations. In adults younger than 65 years of age, influenza-associated hospitalisations and primary care visits roughly increased with age, with the highest excess in the 60-64-year-olds; also influenza-associated mortality was highest in this age group. * RSV-associated hospitalisation rates were highest for the youngest children, although the excess was also substantial in 50-64-year-olds with high-risk conditions and the elderly. In elderly persons, RSV-active periods were associated with excess mortality. * The PRIMAKid-trial demonstrated that influenza vaccination with or without pneumococcal conjugate vaccination reduced confirmed influenza by about 50% and AOM episodes by 57 to 71% during influenza season. This means that between 20 and 25 children are required to be vaccinated in order to prevent one influenza episode; for AOM this number is 19-22 during the influenza season. The effects on febrile RTI in general appeared less during influenza seasons and effects of vaccinations were absent outside the influenza seasons.