Vaccine-preventable diseases: evaluation of vaccination programmes and optimisation of surveillance

Abstract

The Netherlands has a National Immunisation Programme (NIP) and a seasonal influenza vaccination programme. Surveillance enables countries to monitor and assess the impact of these programmes. Dutch surveillance is coordinated by the Centre for Infectious Disease Control and consists of 5 pillars, i.e. assessment of vaccination coverage and safety-, disease-, pathogen- and immune-surveillance. In-depth research can be required to obtain additional data. This thesis contains epidemiological studies on several aspects of vaccine safety and surveillance of vaccine preventable diseases (VPDs) in the Netherlands. Mandatory notification data and information on hospitalisations were used to retrospectively assess trends in pertussis disease in relation to changes in the vaccination schedule. This was used to guide vaccine policy. Through linking of different data sources we studied more severe disease courses and revealed a substantial underreporting of pertussis hospitalisations and death. Unfortunately, linking was hampered by inaccurate linking variables. In a medical record study of infant pertussis hospitalisations, we found an overrepresentation of preterm infants. This group showed a more severe disease course and a lower vaccine-effectiveness. Closer monitoring of preterms is warranted but currently preterms cannot be identified with routine surveillance instruments. In studies on effectiveness and tolerability of an early Measles-Mumps-Rubella vaccination (MMR0), offered to 6-14-month-olds during the 2013-2014 measles outbreak, we used the centralized NIP vaccination registry to invite parents and verify the infant’s vaccination status, which was efficient and increased data reliability. MMR0 proved safe and effective. We also studied the safety of pandemic influenza A(H1N1) vaccination. We demonstrated that this pandemic vaccination was safe not only in combination with prior seasonal influenza vaccination but also when administered during pregnancy. Unfortunately, vaccination status could not be verified. Furthermore, linking questionnaire data of pregnant women to the national Perinatal Registry was challenging. Making use of a large electronic medical record database, we assessed background incidence (IR) of Guillain-Barré Syndrome and Multiple Sclerosis. This is important information to assess possible vaccine safety concerns. It helps to separate legitimate safety concerns from events that are temporally associated but not causally related to the vaccination. Usefulness of those registries can be increased if data become available more real-time and accurate linking to vaccination registries would be possible without great risk of bias. Using data of a nationwide serosurvey (2006-2007), we showed that the general Dutch population is well protected against poliomyelitis. In contrast, Orthodox Protestants are at risk in case poliovirus should be introduced in the area of low vaccination coverage. Likewise, a study on the added value of a bedside test to assess tetanus immunity showed good protection against tetanus with the opportunity to widen the interval of tetanus booster vaccinations. VPD surveillance in the Netherlands has a long track record of high quality data. Due to the need for more detailed and timely results and increased emphasis on privacy, VPD surveillance risks falling short of expectations. Therefore, increased efforts to renew the surveillance systems are very important.