Considerable doubt about rubella screening and vaccination among unvaccinated orthodox protestant women: a mixed-methods study.

BACKGROUND: Women who are susceptible to rubella are advised to vaccinate against rubella to prevent infection in future pregnancies, and thus avert the risk of congenital rubella syndrome in their unborn child. Rubella outbreaks periodically occur in the under-vaccinated orthodox Protestant community in the Netherlands. The objective of this mixed-methods study was to determine and understand personal experience with rubella, perceived rubella susceptibility, and intention to accept rubella screening and vaccination among unvaccinated orthodox Protestant women. The ultimate aim of this study was to inform policy and practice and contribute to the prevention of cases of congenital rubella syndrome. METHODS: A mixed-methods study was conducted combining an online survey and semi-structured interviews among unvaccinated Dutch orthodox Protestant women aged 18-40 years. Descriptive analysis was used for quantitative data. Qualitative data was analysed using codes and categories. RESULTS: Results of the survey (167 participants) showed that most participants had personal experience with rubella (74%, 123/167) and 101 women (61%, 101/167) indicated they had had rubella themselves. More than half of the women were undecided whether to accept rubella susceptibility screening (56%; 87/156) or rubella vaccination (55%; 80/146). Qualitative findings (10 participants) showed that most women thought they were not susceptible to rubella. Indecisiveness and negative attitudes to accept rubella vaccination were related with religious arguments to object vaccination and with women's perception of absence of imminent threat of rubella. Furthermore, results showed presence of misconceptions among women in the interpretation of their susceptibility and high confidence in their parents' memory that they had experienced rubella as a child although no laboratory screening had been conducted. CONCLUSIONS: In light of an imminent rubella outbreak in the Netherlands, a tailored education campaign should be prepared aimed at and established in cooperation with the under-vaccinated orthodox Protestant community. Health care providers should provide adequate information on rubella and support decision-making in order to stimulate women to make a deliberate and informed decision on rubella screening and, if necessary, subsequent vaccination.

Vaccine Impact and Effectiveness of Meningococcal Serogroup ACWY Conjugate Vaccine Implementation in the Netherlands: A Nationwide Surveillance Study.

BACKGROUND: In response to the recent serogroup W invasive meningococcal disease (IMD-W) epidemic in the Netherlands, meningococcal serogroup C (MenC) conjugate vaccination for children aged 14 months was replaced with a MenACWY conjugate vaccination, and a mass campaign targeting individuals aged 14-18 years was executed. We investigated the impact of MenACWY vaccination implementation in 2018-2020 on incidence rates and estimated vaccine effectiveness (VE). METHODS: We extracted IMD cases diagnosed between July 2014 and December 2020 from the national surveillance system. We calculated age group-specific incidence rate ratios by comparing incidence rates before (July 2017-March 2018) and after (July 2019-March 2020) MenACWY vaccination implementation. We estimated VE in vaccine-eligible cases using the screening method. RESULTS: Overall, the IMD-W incidence rate declined by 61% (95% confidence interval [CI], 40 to 74). It declined by 82% (95% CI, 18 to 96) in the vaccine-eligible age group (individuals aged 15-36 months and 14-18 years) and by 57% (95% CI, 34 to 72) in vaccine-noneligible age groups. VE was 92% (95% CI, -20 to 99.5) in vaccine-eligible toddlers (aged 15-36 months). No IMD-W cases were reported in vaccine-eligible teenagers after the campaign. CONCLUSIONS: The MenACWY vaccination program was effective in preventing IMD-W in the target population. The IMD-W incidence reduction in vaccine-noneligible age groups may be caused by indirect effects of the vaccination program. However, disentangling natural fluctuation from vaccine effect was not possible. Our findings encourage the use of toddler and teenager MenACWY vaccination in national immunization programs.

An unusual outbreak in the Netherlands: community-onset impetigo caused by a meticillin-resistant Staphylococcus aureus with additional resistance to fusidic acid, June 2018 to January 2020.

In this retrospective observational study, we analysed a community outbreak of impetigo with meticillin-resistant Staphylococcus aureus (MRSA), with additional resistance to fusidic acid (first-line treatment). The outbreak occurred between June 2018 and January 2020 in the eastern part of the Netherlands with an epidemiological link to three cases from the north-western part. Forty nine impetigo cases and eight carrier cases were identified, including 47 children. All but one impetigo case had community-onset of symptoms. Pharmacy prescription data for topical mupirocin and fusidic acid and GP questionnaires suggested an underestimated outbreak size. The 57 outbreak isolates were identified by the Dutch MRSA surveillance as MLVA-type MT4627 and sequence type 121, previously reported only once in 2014. Next-generation sequencing revealed they contained a fusidic acid resistance gene, exfoliative toxin genes and an epidermal cell differentiation inhibitor gene. Whole-genome multilocus sequence typing revealed genetic clustering of all 19 sequenced isolates from the outbreak region and isolates from the three north-western cases. The allelic distances between these Dutch isolates and international isolates were high. This outbreak shows the appearance of community-onset MRSA strains with additional drug resistance and virulence factors in a country with a low prevalence of antimicrobial resistance.

Evaluation of the surveillance system for invasive meningococcal disease (IMD) in the Netherlands, 2004-2016.

BACKGROUND: Enhanced surveillance for confirmed cases of invasive meningococcal disease (IMD) was introduced in the Netherlands in 2003, in which reference laboratory data (NRLBM) are linked with notification data (OSIRIS). The quality of surveillance information is important for public health decision making. Our objective was to describe the system and evaluate it for data completeness and timeliness. METHODS: Cases reported in the surveillance system from 2004 to 2016 were included. For the notification data, we used information on serogroup, vaccination status, mortality, and country of infection as indicators for record completeness. Notification times to regional and national level were calculated using the reported dates available in the notification database. RESULTS: A total of 2123 cases were reported in the years 2004-2016, of which 1.968 (93%) were reported by the reference laboratory and 1.995 (94%) in the notification system. Of all cases, 1.840 cases (87%) were reported in both systems and could be linked. The serogroup was known in 86% of the notified cases, and was significantly higher (94%) in the years 2013-2016. Information on vaccination status, mortality and country of infection was available in 88, 99 and 97% of notified cases, respectively. Regional notification of cases occurred within one working day for 86% of cases and 98% were notified nationally within three days. CONCLUSIONS: A well performing IMD surveillance system was demonstrated and serogroup completeness has improved over the years. Underlining the need for reporting to both the clinical and laboratory surveillance system remains important to further improve the overall performance in supporting public health response and vaccination policy.

Two Community Clusters of Legionnaires' Disease Directly Linked to a Biologic Wastewater Treatment Plant, the Netherlands.

A biologic wastewater treatment plant was identified as a common source for 2 consecutive Legionnaires' disease clusters in the Netherlands in 2016 and 2017. Sequence typing and transmission modeling indicated direct and long-distance transmission of Legionella, indicating this source type should also be investigated in sporadic Legionnaires' disease cases.

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.

Large measles epidemic in the Netherlands, May 2013 to March 2014: changing epidemiology.

Since the early 1990s, the Netherlands has experienced several large measles epidemics, in 1992-94, 1999-2000 and in 2013-14. These outbreaks mainly affected orthodox Protestants, a geographically clustered population with overall lower measles-mumps-rubella first dose (MMR-1) vaccination coverage (60%) than the rest of the country (> 95%). In the 2013-14 epidemic described here, which occurred between 27 May 2013 and 12 March 2014, 2,700 cases were reported. Several control measures were implemented including MMR vaccination for 6-14-month-olds and recommendations to reduce the risk in healthcare workers. The vast majority of reported cases were unvaccinated (94%, n = 2,539), mostly for religious reasons (84%, n = 2,135). The median age in the epidemic was 10 years, 4 years older than in the previous epidemic in 1999-2000. A likely explanation is that the inter-epidemic interval before the 2013-2014 epidemic was longer than the interval before the 1999-2000 epidemic. The size of the unvaccinated orthodox Protestant community is insufficient to allow endemic transmission of measles in the Netherlands. However, large epidemics are expected in the future, which is likely to interfere with measles elimination in the Netherlands and elsewhere.

Negative attitude and low intention to vaccinate universally against varicella among public health professionals and parents in the Netherlands: two internet surveys.

BACKGROUND: Prior to introduction of universal varicella vaccination, it is crucial to gain insight into the willingness to vaccinate among the population. This is because suboptimal national vaccination coverage might increase the age of infection in children, which will lead to higher complication rates. We studied the attitude and intention to vaccinate against varicella among Dutch public health professionals who execute the National Immunisation Programme (NIP), and parents. METHODS: Medical doctors and nurses of regional public health services (RPHS) and child health clinics (CHC), and a random sample of parents received an internet survey on varicella vaccination. Separate logistic regression models were used to identify determinants for a positive attitude (professionals) or a positive intention (parents) to vaccinate against varicella within the NIP (free of charge). RESULTS: The questionnaire was completed by 181 RPHS professionals (67%), 260 CHC professionals (46%), and 491 parents (33%). Of professionals, 21% had a positive attitude towards universal varicella vaccination, while 72% preferred to limit vaccination to high-risk groups only. Of parents, 28% had a positive intention to vaccinate their child against varicella within the NIP. The strongest determinant for a positive attitude or intention to vaccinate against varicella among professionals and parents was the belief that varicella is a disease serious enough to vaccinate against. CONCLUSIONS: We showed that a majority of the Dutch public health professionals and parents in this study have a negative attitude or low intention to vaccinate universally against varicella, as a result of the perceived low severity of the disease. Most participating professionals support selective vaccination to prevent varicella among high-risk groups.

Economic Costs of Measles Outbreak in the Netherlands, 2013-2014.

In 2013 and 2014, the Netherlands experienced a measles outbreak in orthodox Protestant communities with low measles-mumps-rubella vaccination coverage. Assessing total outbreak costs is needed for public health outbreak preparedness and control. Total costs of this outbreak were an estimated $4.7 million.

Determinants of students' willingness to accept a measles-mumps-rubella booster vaccination during a mumps outbreak: a cross-sectional study.

BACKGROUND: Despite high vaccination coverage, a mumps outbreak that affected mainly vaccinated university students and their contacts took place in the Netherlands in the period 2009-2012. We presented university students with a hypothetical case in which we offered them a measles, mumps, and rubella (MMR) booster vaccination to control the mumps outbreak. The aim of this study was to get insight into the determinants of university students' willingness to accept this vaccination. METHODS: A questionnaire containing 38 items was developed for the purpose of assessing students' willingness and the psychosocial and social demographic determinants influencing their willingness to accept an MMR booster vaccination. In addition, we explored how organisational characteristics influenced the willingness to be vaccinated. Data were collected at six Dutch universities; a total of 790 students from various faculties were invited to participate. This was a convenience sampling procedure. RESULTS: 687 university students participated (response rate 87.0%) and 60.4% of the participants said they would be willing accept the hypothetical MMR booster vaccination. The perceived seriousness of mumps (OR 6.1) was the most important predictor of willingness to accept vaccination. Students who expected the MMR vaccination to be effective and to prevent individual illness and who believed their own vaccination would help stop the epidemic were more likely to be willing than others. The students were more willing to accept vaccination when they perceived that the social norms of significant others and the government favoured vaccination. Organisational characteristics, such as offering vaccination cost free and offering it at the university site, increased students' willingness. CONCLUSION: During a mumps outbreak, university students were generally willing to accept a hypothetical MMR booster vaccination. Risk perception, outcome expectations, perceived social norms, and organisational characteristics should be taken into account in the planning of any vaccination campaign for university students during an outbreak of an infectious disease.

Vaccination coverage for measles, mumps and rubella in anthroposophical schools in Gelderland, The Netherlands.

BACKGROUND: Social clustering of unvaccinated children in anthroposophical schools occurs, as inferred from various measles outbreaks that can be traced to these schools. However, accurate vaccination coverage data of anthroposophical schools are not widely available. METHODS: In 2012, we performed a survey to estimate the vaccination coverage in three different grades of 11 anthroposophical schools in Gelderland, The Netherlands. We also gauged the opinion on childhood vaccination of the parents and compared these with the results of a national survey. In 2014, we were also able to obtain the registered total vaccination coverage per school from the national vaccination register to compare this with our survey data. RESULTS: The self-reported MMR vaccination coverage (2012) in the three grades of the schools in our study was 83% (range 45-100% per school). The registered total vaccination coverage (2014) was 78% (range 59-88% per school). The 95% confidence intervals of the two different vaccination coverages overlap for all schools. The parents in this study were less convinced about the beneficial effect of vaccinations and more worried about the possible side effects of vaccination compared with parents in general. CONCLUSION: Despite high overall vaccination coverage, the WHO goal to eliminate measles and rubella will not easily be achieved when social clustering of unvaccinated children in anthroposophical schools remains.

Estimation of vaccine efficacy and critical vaccination coverage in partially observed outbreaks.

Classical approaches to estimate vaccine efficacy are based on the assumption that a person's risk of infection does not depend on the infection status of others. This assumption is untenable for infectious disease data where such dependencies abound. We present a novel approach to estimating vaccine efficacy in a Bayesian framework using disease transmission models. The methodology is applied to outbreaks of mumps in primary schools in the Netherlands. The total study population consisted of 2,493 children in ten primary schools, of which 510 (20%) were known to have been infected, and 832 (33%) had unknown infection status. The apparent vaccination coverage ranged from 12% to 93%, and the apparent infection attack rate varied from 1% to 76%. Our analyses show that vaccination reduces the probability of infection per contact substantially but not perfectly ([Formula: see text] = 0.933; 95CrI: 0.908-0.954). Mumps virus appears to be moderately transmissible in the school setting, with each case yielding an estimated 2.5 secondary cases in an unvaccinated population ([Formula: see text] = 2.49; 95%CrI: 2.36-2.63), resulting in moderate estimates of the critical vaccination coverage (64.2%; 95%CrI: 61.7-66.7%). The indirect benefits of vaccination are highest in populations with vaccination coverage just below the critical vaccination coverage. In these populations, it is estimated that almost two infections can be prevented per vaccination. We discuss the implications for the optimal control of mumps in heterogeneously vaccinated populations.

The role of religious leaders in promoting acceptance of vaccination within a minority group: a qualitative study.

BACKGROUND: Although childhood vaccination programs have been very successful, vaccination coverage in minority groups may be considerably lower than in the general population. In order to increase vaccination coverage in such minority groups involvement of faith-based organizations and religious leaders has been advocated. We assessed the role of religious leaders in promoting acceptance or refusal of vaccination within an orthodox Protestant minority group with low vaccination coverage in The Netherlands. METHODS: Semi-structured interviews were conducted with orthodox Protestant religious leaders from various denominations, who were selected via purposeful sampling. Transcripts of the interviews were thematically analyzed, and emerging concepts were assessed for consistency using the constant comparative method from grounded theory. RESULTS: Data saturation was reached after 12 interviews. Three subgroups of religious leaders stood out: those who fully accepted vaccination and did not address the subject, those who had religious objections to vaccination but focused on a deliberate choice, and those who had religious objections to vaccination and preached against vaccination. The various approaches of the religious leaders seemed to be determined by the acceptance of vaccination in their congregation as well as by their personal point of view. All religious leaders emphasized the importance of voluntary vaccination programs and religious exemptions from vaccination requirements. In case of an epidemic of a vaccine preventable disease, they would appreciate a dialogue with the authorities. However, they were not willing to promote vaccination on behalf of authorities. CONCLUSION: Religious leaders' attitudes towards vaccination vary from full acceptance to clear refusal. According to orthodox Protestant church order, local congregation members appoint their religious leaders themselves. Obviously they choose leaders whose views are compatible with the views of the congregation members. Moreover, the positions of orthodox Protestant religious leaders on vaccination will not change easily, as their objections to vaccination are rooted in religious doctrine and they owe their authority to their interpretation and application of this doctrine. Although the dialogue with religious leaders that is pursued by the Dutch government may be helpful in controlling epidemics by other means than vaccination, it is unlikely to increase vaccination coverage.

How orthodox protestant parents decide on the vaccination of their children: a qualitative study.

BACKGROUND: Despite high vaccination coverage, there have recently been epidemics of vaccine preventable diseases in the Netherlands, largely confined to an orthodox protestant minority with religious objections to vaccination. The orthodox protestant minority consists of various denominations with either low, intermediate or high vaccination coverage. All orthodox protestant denominations leave the final decision to vaccinate or not up to their individual members. METHODS: To gain insight into how orthodox protestant parents decide on vaccination, what arguments they use, and the consequences of their decisions, we conducted an in-depth interview study of both vaccinating and non-vaccinating orthodox protestant parents selected via purposeful sampling. The interviews were thematically coded by two analysts using the software program Atlas.ti. The initial coding results were reviewed, discussed, and refined by the analysts until consensus was reached. Emerging concepts were assessed for consistency using the constant comparative method from grounded theory. RESULTS: After 27 interviews, data saturation was reached. Based on characteristics of the decision-making process (tradition vs. deliberation) and outcome (vaccinate or not), 4 subgroups of parents could be distinguished: traditionally non-vaccinating parents, deliberately non-vaccinating parents, deliberately vaccinating parents, and traditionally vaccinating parents. Except for the traditionally vaccinating parents, all used predominantly religious arguments to justify their vaccination decisions. Also with the exception of the traditionally vaccinating parents, all reported facing fears that they had made the wrong decision. This fear was most tangible among the deliberately vaccinating parents who thought they might be punished immediately by God for vaccinating their children and interpreted any side effects as a sign to stop vaccinating. CONCLUSIONS: Policy makers and health care professionals should stimulate orthodox protestant parents to make a deliberate vaccination choice but also realize that a deliberate choice does not necessarily mean a choice to vaccinate.

Measuring vaccination coverage in a hard to reach minority.

BACKGROUND: Although childhood vaccination programmes have been very successful, there are some hard to reach minority groups that object to vaccination. The Netherlands has experienced several epidemics of vaccine-preventable diseases, confined to the orthodox Protestant minority. However, vaccination coverage in this minority is still unknown and this hampers prevention and control of epidemics. METHODS: We estimated vaccination coverage among the orthodox Protestant minority and its various subgroups (denominations), using two sub-studies with different design and study population. For both sub-studies separately, we determined overall vaccination coverage and vaccination coverage per denomination. The results were compared and discussed. RESULTS: An online survey was filled out by 1778 orthodox Protestant youngsters, invited via orthodox Protestant media using a snowball method. Next to that, results of a national sample study on vaccination were used, of which only orthodox Protestant respondents were included in our analyses (N = 2129). Overall vaccination coverage among orthodox Protestants in The Netherlands was estimated to be at minimum 60%. Moreover, in both sub-studies three clusters of denominations could be identified, with high (>85%), intermediate (50-75%) and low (<25%) vaccination coverage. CONCLUSION: The integration of both sub-studies, with their own specific strengths and weaknesses, added to our insight in the vaccination coverage in this minority. Based on these results, we recommend to focus prevention and control of vaccine-preventable diseases on the orthodox Protestant subgroups with intermediate and low vaccination coverage.

How healthcare professionals respond to parents with religious objections to vaccination: a qualitative study.

BACKGROUND: In recent years healthcare professionals have faced increasing concerns about the value of childhood vaccination and many find it difficult to deal with parents who object to vaccination. In general, healthcare professionals are advised to listen respectfully to the objections of parents, provide honest information, and attempt to correct any misperceptions regarding vaccination. Religious objections are one of the possible reasons for refusing vaccination. Although religious objections have a long history, little is known about the way healthcare professionals deal with these specific objections. The aim of this study is to gain insight into the responding of healthcare professionals to parents with religious objections to the vaccination of their children. METHODS: A qualitative interview study was conducted with health care professionals (HCPs) in the Netherlands who had ample experience with religious objections to vaccination. Purposeful sampling was applied in order to include HCPs with different professional and religious backgrounds. Data saturation was reached after 22 interviews, with 7 child health clinic doctors, 5 child health clinic nurses and 10 general practitioners. The interviews were thematically analyzed. Two analysts coded, reviewed, discussed, and refined the coding of the transcripts until consensus was reached. Emerging concepts were assessed using the constant comparative method from grounded theory. RESULTS: Three manners of responding to religious objections to vaccination were identified: providing medical information, discussion of the decision-making process, and adoption of an authoritarian stance. All of the HCPs provided the parents with medical information. In addition, some HCPs discussed the decision-making process. They verified how the decision was made and if possible consequences were realized. Sometimes they also discussed religious considerations. Whether the decision-making process was discussed depended on the willingness of the parents to engage in such a discussion and on the religious background, attitudes, and communication skills of the HCPs. Only in cases of tetanus post-exposure-prophylaxis, general practitioners reported adoption of an authoritarian stance. CONCLUSION: Given that the provision of medical information is generally not decisive for parents with religious objections to vaccination, we recommend HCPs to discuss the vaccination decision-making process, rather than to provide them with extra medical information.

The role of schools in the spread of mumps among unvaccinated children: a retrospective cohort study.

BACKGROUND: In the Netherlands, epidemics of vaccine preventable diseases are largely confined to an orthodox protestant minority with religious objections to vaccination. The clustering of unvaccinated children in orthodox protestant schools can foster the spread of epidemics. School closure has nevertheless not been practiced up until now. A mumps epidemic in 2007-2008 gave us an opportunity to study the role of schools in the spread of a vaccine preventable disease in a village with low vaccination coverage. METHODS: A retrospective cohort study was conducted among the students in four elementary schools and their siblings. The following information was collected for each child: having had the mumps or not and when, school, age, MMR vaccination status, household size, presence of high school students in the household, religious denomination, and home village. The spread of mumps among unvaccinated children was compared for the four schools in a Kaplan-Meier analysis using a log-rank test. Cox proportional hazard analyses were performed to test for the influence of other factors. To correct for confounding, a univariate Cox regression model with only school included as a determinant was compared to a multivariate regression model containing all possible confounders. RESULTS: Out of 650 households with children at the schools, 54% completed a questionnaire, which provided information on 1191 children. For the unvaccinated children (N = 769), the Kaplan-Meier curves showed significant differences among the schools in their cumulative attack rates. After correction for confounding, the Cox regression analysis showed the hazard of mumps to be higher in one orthodox protestant school compared to the other (hazard ratio 1.43, p < 0.001). Household size independently influenced the hazard of mumps (hazard ratio 1.44, p < 0.005) with children in larger households running a greater risk. CONCLUSION: If and when unvaccinated children got mumps was determined by the particular school the children and their siblings attended, and by the household size. This finding suggests that school closure can influence the spread of an epidemic among orthodox protestant populations, provided that social distancing is adhered to as well. Further research on the effects of school closure on the final attack rate is nevertheless recommended.

Religious subgroups influencing vaccination coverage in the Dutch Bible belt: an ecological study.

BACKGROUND: The Netherlands has experienced epidemics of vaccine preventable diseases largely confined to the Bible belt, an area where -among others- orthodox protestant groups are living. Lacking information on the vaccination coverage in this minority, and its various subgroups, control of vaccine preventable diseases is focused on the geographical area of the Bible belt. However, the adequacy of this strategy is questionable. This study assesses the influence of presence of various orthodox protestant subgroups (orthodox protestant denominations, OPDs) on municipal vaccination coverage in the Bible belt. METHODS: We performed an ecological study at municipality level. Data on number of inhabitants, urbanization level, socio-economical status, immigration and vaccination coverage were obtained from national databases. As religion is not registered in the Netherlands, membership numbers of the OPDs had to be obtained from church year books and via church offices. For all municipalities in the Netherlands, the effect of presence or absence of OPDs on vaccination coverage was assessed by comparing mean vaccination coverage. For municipalities where OPDs were present, the effect of each of them (measured as membership ratio, the number of members proportional to total number of inhabitants) on vaccination coverage was assessed by bivariate correlation and multiple regression analysis in a model containing the determinants immigration, socio-economical status and urbanization as well. RESULTS: Mean vaccination coverage (93.5% ± 4.7) in municipalities with OPDs (n = 135) was significantly lower (p < 0.001) than in 297 municipalities without OPDs (96.9% ± 2.1). Multiple regression analyses showed that in municipalities with OPDs 84% of the variance in vaccination coverage was explained by the presence of these OPDs. Immigration had a significant, but small explanatory effect as well. Membership ratios of all OPDs were negatively related to vaccination coverage; this relationship was strongest for two very conservative OPDs. CONCLUSION: As variance in municipal vaccination coverage in the Bible belt is largely explained by membership ratios of the various OPDs, control of vaccine preventable diseases should be focused on these specific risk groups. In current policy part of the orthodox protestant risk group is missed.