In PIENTER2 24,147 persons were invited and 7904 (33%) donated a blood sample (Figs ?(Figs11 and ?and2)2) [6C9]. Open in a separate window Fig 1 Flowchart of LY2140023 (LY404039) the PIENTER1 study population.The number of persons invited to participate in the PIENTER1 study and the number actually included in the GMC ratio (dashed line) and the determinant calculations (dotted line). Open in a separate window Fig 2 Flowchart of the PIENTER2 study population.The number of persons invited to participate in the PIENTER2 study and the number of participants actually included in the GMC ratio (dashed line) and the determinant calculations (dotted line). a blood sample and completed a questionnaire. Pneumococcal antibodies of serotypes included in PCV13 were measured with a fluorescent-bead based multiplex immunoassay. Geometric mean antibody concentrations (GMCs) and determinants of pneumococcal antibody levels were investigated. Results GMCs were higher in PIENTER2 for serotypes 1, 6A, 6B, 9V, 18C, 19F and 23F and lower for 3 and 5. Age, day care attendance, household size, vaccination coverage, and urbanisation rate were associated with pneumococcal antibodies in children. Education level, ethnicity, age, low vaccination coverage sample, urbanisation rate, and asthma/COPD were associated with pneumococcal antibodies in elderly. The determinants significantly associated with pneumococcal IgG were slightly different for the elderly in PIENTER1 compared to the elderly in PIENTER2. Conclusion Although most of the serotype antibody levels remained stable, some of the serotype-specific antibody levels varied during the pre-vaccine era, indicating that exposure of certain serotypes changes without interference of PCVs. Introduction is an important cause of meningitis, pneumonia and bacteraemia in young children and elderly [1C3]. The pneumococcus is usually a common resident of the nasopharynx of humans and especially in children. Colonisation can precede transmission from human to human, an antibody response against the colonising serotype, and development of pneumococcal disease [4]. Children are the most important reservoir of this pathogen; they can transmit the pneumococcus to other children, adults and elderly [4]. In order to prevent invasive pneumococcal disease (IPD) in children, many countries have added the pneumococcal conjugate vaccine (PCV) to their LY2140023 (LY404039) national immunisation program (NIP) [1C3]. The PCVs currently target a maximum of 13 serotypes, while >90 serotypes are known [4]. Vaccination of infants blocks transmission of vaccine serotypes to other age groups. PCVs are highly effective in preventing IPD caused by the vaccine serotypes, but the number of IPD cases caused by non-vaccine serotypes has been rising [1, 5]. In order LY2140023 (LY404039) to understand the effects of vaccination around the distribution of serotypes causing pneumococcal disease, it is Vezf1 important to investigate the dynamics of the different pneumococcal serotypes in the pre-vaccine era. Knowledge on serotype specific transmission over time provides information about the potential spread of non-vaccine serotypes now colonizing the infants. Also, it is relevant to investigate whether the risk factors for acquiring the pneumococcus change over time independently of vaccination to better interpret possible changes after introduction of vaccination. Serosurveillance studies conducted at different points in time in the pre-vaccine period could shed light on possible changes in the antibody levels in the absence of vaccination. Such studies provide a base line measurement before the vaccine implementation and could help to evaluate the effects observed after implementation. The presence of antibodies shows that the individual has at least once encountered the specific serotype and the serotype was able to induce an antibody response. While carriage studies provide important insights in the prevalence of serotypes in the nasopharynx they provide often more a snapshot. Also, serosurveillance studies allow for the measurement of a high number of subjects. In this study we compared the results of two serosurveillance studies conducted in the Netherlands in 1995C1996 and 2006C2007, with the aim of eventually comparing these results with post-vaccine studies for both carriage and serosurveillance. The 7-valent PCV was added to the NIP in April 2006 and no national catch-up campaign was organized. Therefore almost all participants were not vaccinated with PCV except a small group of 0C1 year aged children of whom only 9 received the booster vaccination [6]. We investigated changes.