Risk factors for persisting measles susceptibility: a case-control study among unvaccinated orthodox Protestants.

Background: Measles is an infectious disease providing lifelong immunity. Epidemics periodically occur among unvaccinated orthodox Protestants in the Netherlands. During the 2013/2014 epidemic, 17% of the reported patients was over 14 years old. Apparently, they did not catch measles during the previous 1999/2000 epidemic and remained susceptible. We wanted to identify risk factors for this so-called persisting measles susceptibility, and thus risk factors for acquiring measles at older age with increased risk of complications. Methods: A case-control study was performed among unvaccinated orthodox Protestants born between 1988 and 1998; cases had measles in 2013/2014, controls during or before 1999/2000. Associations between demographic, geographical and religion-related determinants and persisting measles susceptibility were determined using univariate and multivariable logistic regression. Analyses were stratified in two age-groups: infants/toddlers and primary school-aged children during the 1999/2000 measles epidemic. Results: In total, 204 cases and 563 controls were included. Risk factors for persisting measles susceptibility for infants/toddlers in 1999/2000 were belonging to a moderately conservative church, absence of older siblings and residency outside low vaccination coverage (LVC)-municipalities. Risk factors for primary school-aged children were residency outside LVC-municipalities and attendance of non-orthodox Protestant primary school. Conclusion: Unvaccinated orthodox Protestant adolescents and adults who resided outside the LVC-municipalities, did not attend an orthodox Protestant primary school, had no older siblings and belonged to a moderately conservative church were at risk for persisting measles susceptibility and, thus, for acquiring measles at older age with increased risk of complications. For this subgroup of orthodox Protestants targeted information on vaccination is recommended.

Increase in vaccination coverage between subsequent generations of orthodox Protestants in The Netherlands.

Background: The Netherlands experienced several outbreaks of vaccine preventable diseases, largely confined to an orthodox Protestant minority group. Based on religious arguments some orthodox Protestants accept vaccination, while others refuse. Their acceptance of vaccination, however, seems to be changing over time. We estimated vaccination coverage in subsequent generations of orthodox Protestants and identified determinants of the intention to vaccinate their (future) children. In 2013 orthodox Protestants in the age of 18-40 years were invited to fill out an online questionnaire on their own vaccination status, vaccination status of their parents, the vaccination status or vaccination intention for their (future) children, and possible determinants of the intention to vaccinate (future) children. Vaccination coverage of respondents' parents and respondents was compared using chi-square tests. Logistic regression was used to identify determinants associated with vaccination of (future) children. In total, 981 orthodox Protestant respondents were included in the study. Vaccination coverage among the parents of respondents was 40.1% (95% CI 37.8-42.5%), among respondents 55.3% (95% CI 52.2-58.4%). This means an increase of 15.2% in one generation ( P < 0.001). About 65% of respondents vaccinated or intends to vaccinate their (future) children. Multivariate logistic regression showed that strongest predictors for vaccinating (future) children were low or moderate level of religious conservatism (OR 10.4 [95% CI 5.7-18.9] and 4.6 [95% CI 2.9-7.4], respectively), being vaccinated themselves (OR 6.0 [95% CI 4.3-8.5]) and high educational level (OR 2.5 [95% CI 1.6-4.0]). Vaccination coverage among Dutch orthodox Protestants is increasing over time.