Phd ceremony Ms. G. Gefenaite:Newly introduced vaccines. Effectiveness and determinants of acceptance

Since the beginning of the twentieth century, many infectious diseases have been controlled by large scale vaccination programs. Nevertheless, current vaccination programs in Europe face challenges due to concerns regarding vaccine effectiveness. In this thesis the effectiveness of newly introduced vaccination campaigns and the determinants of their acceptance were assessed. The routine assessment of influenza vaccination campaigns in the Netherlands, Lithuania and across multiple countries and years using novel methods confirmed that influenza vaccines were quite effective. For example, it prevented approximately 30% to 80% of influenza-related outcomes in senior populations. Besides influenza, Streptococcus pneumoniae is also one of the leading causes of respiratory diseases. Vaccination against this bacterium showed to be preventive against respiratory antibiotic use, especially in children aged three and four. Additionally, we found that the Q fever vaccine was nearly 100% effective in preventing the disease in relatively healthy subjects. Its effectiveness in risk groups such as pregnant women, immunocompromised persons or those with pre-existing cardiac valve- or vessel defects, is still to be determined. Despite relatively high vaccine effectiveness estimates found in the abovementioned studies, future research should focus on addressing the remaining methodological challenges to provide more accurate effectiveness estimates in different populations. Furthermore, knowing that the vaccine was effective doubled influenza vaccine acceptance in health care workers and increased acceptance of the vaccine against Human Papillomavirus by more than seven-fold in teenage girls. Information regarding vaccine effectiveness should therefore be implemented in vaccination information campaigns.