How to increase awareness of additional vaccinations; the case of maternal pertussis vaccination.

BACKGROUND: Effective and safe vaccines are available outside national immunization programs (NIP). Increased awareness and vaccine uptake can improve public health. Before the inclusion of maternal pertussis vaccination (MPV) in the Dutch NIP in December 2019, extra communication efforts were undertaken. Here we examine the success of these efforts, investigating women's awareness of and their decision-making process regarding MPV. METHODS: Between December 2018 and January 2019, one year before the introduction of MPV in the NIP, and about three years after MPV was recommended by the Dutch Health Council, pregnant and non-pregnant women (i.e. child younger than two years) were invited to fill out an online questionnaire. Participant's decision-making processes regarding MPV were assessed with an adapted Precaution Adoption Process Model (PAPM), including stages of awareness, engagement, information-seeking, and vaccination behaviour. Furthermore, factors related to the decision-making process were examined. RESULTS: In total, 942 women were included, of whom 62% were non-pregnant. Most of the pregnant and nonpregnant women were aware of MPV during pregnancy (respectively 69 and 56%). Most aware women had heard about MPV through their midwife and the Public Health Institute (PHI) website. Women unaware of MPV reported a need for information, preferably from their midwives. Most aware women felt MPV was important to them (88%) and were classified as "engaged". Of the eligible and "engaged" pregnant women, 58% were vaccinated, versus 38% of "engaged" non-pregnant women. CONCLUSIONS: As the most preferred and trusted source of information, midwives are essential to increasing awareness of MPV. The PHI website is considered to be a reliable information source and is often consulted. To increase awareness, appropriate healthcare workers should be encouraged to actively inform target groups about available, additional vaccinations.

Determinants of HPV-vaccination uptake and subgroups with a lower uptake in the Netherlands.

BACKGROUND: In the Netherlands, the HPV-vaccine uptake was 52% during the 2009 catch-up campaign (birth cohorts 1993-1996). This increased to 61% in the regular immunization program (birth cohorts 2000-2001). However for birth cohorts 2003-2004 the uptake declined to 45.5%. With this study we aimed to gain insight into social, economic and cultural determinants that are associated with HPV-vaccination uptake and which subgroups with a lower HPV-vaccination uptake can be identified. In addition, we investigated whether the influence of these factors changed over time. METHODS: To study the determinants of HPV-vaccine uptake we performed a database study using different aggregation levels, i.e. individual level, postal code level and municipality level. All Dutch girls who were invited for HPV-vaccination through the National Immunization Program in the years 2012, 2014 and 2017 (i.e. birth cohorts 1999, 2001 and 2004, respectively) were included in the study population. We conducted multilevel logistic regression analyses to analyze the influence of the determinants on HPV-vaccination uptake, taking into account that the delivery of HPV-vaccine was nested within municipalities. RESULTS: Results showed that in particular having not received a MMR-vaccination, having one or two parents born in Morocco or Turkey, living in an area with lower socioeconomic status and higher municipal voting proportions for Christian political parties or populist parties with liberal-conservative views were associated with a lower HPV-vaccination uptake. Besides some changes in political preferences of the population and changes in the association between HPV uptake and urbanization level we found no clear determinants which could possibly explain the decrease in the HPV-vaccination uptake. CONCLUSIONS: In this study we identified current social, economic and cultural determinants that are associated with HPV-vaccination uptake and which low-vaccination subgroups can be identified. However, no clear determinants were found which could explain the decrease in the HPV-vaccination uptake. Tailored information and/or consultation for groups that are associated with a lower HPV-vaccination uptake might help to increase the HPV-vaccination uptake in the future.

Effect of vaccination on severity and infectiousness of measles during an outbreak in the Netherlands, 2013-2014.

An outbreak of measles in the Netherlands in 2013-2014 provided an opportunity to assess the effect of MMR vaccination on severity and infectiousness of measles.Measles is notifiable in the Netherlands. We used information on vaccination, hospitalisation, complications, and most likely source(s) of infection from cases notified during the outbreak. When a case was indicated as a likely source for at least one other notified case, we defined it as infectious. We estimated the age-adjusted effect of vaccination on severity and infectiousness with logistic regression.Of 2676 notified cases, 2539 (94.9%) were unvaccinated, 121 (4.5%) were once-vaccinated and 16 (0.6%) were at least twice-vaccinated; 328 (12.3%) cases were reported to have complications and 172 (6.4%) cases were hospitalised. Measles in twice-vaccinated cases led less often to complications and/or hospitalisation than measles in unvaccinated cases (0% and 14.5%, respectively, aOR 0.1 (95% CI 0-0.89), P = 0.03). Of unvaccinated, once-vaccinated and twice-vaccinated cases, respectively, 194 (7.6%), seven (5.1%) and 0 (0%) were infectious. These differences were not statistically significant (P > 0.05).Our findings suggest a protective effect of vaccination on the occurrence of complications and/or hospitalisation as a result of measles and support the WHO recommendation of a two-dose MMR vaccination schedule.

Measuring vaccine effectiveness against persistent HPV infections: a comparison of different statistical approaches.

BACKGROUND: Persistent high-risk human papillomavirus (HPV) infection is endorsed by the World Health Organization as an intermediate endpoint for evaluating HPV vaccine effectiveness/efficacy. There are different approaches to estimate the vaccine effectiveness/efficacy against persistent HPV infections. METHODS: We performed a systematic literature search in Pubmed to identify statistical approaches that have been used to estimate the vaccine effectiveness/efficacy against persistent HPV infections. We applied these methods to data of a longitudinal observational study to assess their performance and compare the obtained vaccine effectiveness (VE) estimates. RESULTS: Our literature search identified four approaches: the conditional exact test for comparing two independent Poisson rates using a binomial distribution, Generalized Estimating Equations for Poisson regression, Prentice Williams and Peterson total time (PWP-TT) and Cox proportional hazards regression. These approaches differ regarding underlying assumptions and provide different effect measures. However, they provided similar effectiveness estimates against HPV16/18 and HPV31/33/45 persistent infections in a cohort of young women eligible for routine HPV vaccination (range VE 93.7-95.1% and 60.4-67.7%, respectively) and seemed robust to violations of underlying assumptions. CONCLUSIONS: As the rate of subsequent infections increased in our observational cohort, we recommend PWP-TT as the optimal approach to estimate the vaccine effectiveness against persistent HPV infections in young women. Confirmation of our findings should be undertaken by applying these methods after longer follow-up in our study, as well as in different populations.

High Effectiveness of the Bivalent Human Papillomavirus (HPV) Vaccine Against Incident and Persistent HPV Infections up to 6 Years After Vaccination in Young Dutch Women.

Background: Monitoring vaccine effectiveness (VE) in vaccination programs is of importance for assessing the impact of immunization. This study aimed to estimate the VE of the bivalent human papillomavirus (HPV) vaccine against incident and 12-month persistent infections up to 6 years after vaccination. Methods: In 2009-2010, girls eligible for the vaccination catch-up campaign (ie, those aged 14-16 years) were enrolled into a prospective cohort. Annually, participants completed a questionnaire and submitted a self-collected vaginal swab sample for HPV testing by the SPF10-LiPA25 assay. We compared sociodemographic characteristics and infection rates between vaccinated and unvaccinated girls. The VE was adjusted for characteristics related to HPV vaccination status. We used combined end points for VE estimation. Results: In total, 1635 women, of whom 54% were fully vaccinated, were included for VE estimation. The adjusted VE against HPV16 and 18 persistent infections amounted to 97.7% (95% confidence interval [CI], 83.5%-99.7%). We found a VE against HPV31, 33, and 45 persistent infections of 61.8% (95% CI, 16.7%-82.5%). We found no indications that the protection against vaccine or cross-protective types changes over time. Conclusion: Our findings of nearly full protection against vaccine-type persistent infections and significant cross-protection to nonvaccine types in a population-based cohort study confirm the effectiveness of the bivalent HPV vaccine as estimated in trials. We found no indications for waning protection up to 6 years after vaccination.

Updated cost-effectiveness and risk-benefit analysis of two infant rotavirus vaccination strategies in a high-income, low-endemic setting.

BACKGROUND AND OBJECTIVE: Since 2013, a biennial rotavirus pattern has emerged in the Netherlands with alternating high and low endemic years and a nearly 50% reduction in rotavirus hospitalization rates overall, while infant rotavirus vaccination has remained below 1% throughout. As the rotavirus vaccination cost-effectiveness and risk-benefit ratio in high-income settings is highly influenced by the total rotavirus disease burden, we re-evaluated two infant vaccination strategies, taking into account this recent change in rotavirus epidemiology. METHODS: We used updated rotavirus disease burden estimates derived from (active) surveillance to evaluate (1) a targeted strategy with selective vaccination of infants with medical risk conditions (prematurity, low birth weight, or congenital conditions) and (2) universal vaccination including all infants. In addition, we added herd protection as well as vaccine-induced intussusception risk to our previous cost-effectiveness model. An age- and risk-group structured, discrete-time event, stochastic multi-cohort model of the Dutch pediatric population was used to estimate the costs and effects of each vaccination strategy. RESULTS: The targeted vaccination was cost-saving under all scenarios tested from both the healthcare payer and societal perspective at rotavirus vaccine market prices (€135/child). The cost-effectiveness ratio for universal vaccination was €51,277 at the assumed vaccine price of €75/child, using a societal perspective and 3% discount rates. Universal vaccination became cost-neutral at €32/child. At an assumed vaccine-induced intussusception rate of 1/50,000, an estimated 1707 hospitalizations and 21 fatal rotavirus cases were averted by targeted vaccination per vaccine-induced intussusception case. Applying universal vaccination, an additional 571 hospitalizations and <  1 additional rotavirus death were averted in healthy children per vaccine-induced intussusception case. CONCLUSION: While universal infant rotavirus vaccination results in the highest reductions in the population burden of rotavirus, targeted vaccination should be considered as a cost-saving alternative with a favorable risk-benefit ratio for high-income settings where universal implementation is unfeasible because of budget restrictions, low rotavirus endemicity, and/or public acceptance.

Quantifying the impact of mass vaccination programmes on notified cases in the Netherlands.

Vaccination programmes are considered a main contributor to the decline of infectious diseases over the 20th century. In recent years, the national vaccination coverage in the Netherlands has been declining, highlighting the need for continuous monitoring and evaluation of vaccination programmes. Our aim was to quantify the impact of long-standing vaccination programmes on notified cases in the Netherlands. We collected and digitised previously unavailable monthly case notifications of diphtheria, poliomyelitis, mumps and rubella in the Netherlands over the period 1919-2015. Poisson regression models accounting for seasonality, multi-year cycles, secular trends and auto-correlation were fit to pre-vaccination periods. Cases averted were calculated as the difference between observed and expected cases based on model projections. In the first 13 years of mass vaccinations, case notifications declined rapidly with 82.4% (95% credible interval (CI): 74.9-87.6) of notified cases of diphtheria averted, 92.9% (95% CI 85.0-97.2) cases of poliomyelitis, and 79.1% (95% CI 67.1-87.4) cases of mumps. Vaccination of 11-year-old girls against rubella averted 49.9% (95% CI 9.3-73.5) of cases, while universal vaccination averted 68.1% (95% CI 19.4-87.3) of cases. These findings show that vaccination programmes have contributed substantially to the reduction of infectious diseases in the Netherlands.

Tolerability of Early Measles-Mumps-Rubella Vaccination in Infants Aged 6-14 Months During a Measles Outbreak in The Netherlands in 2013-2014.

BACKGROUND: In 2013-2014, a measles outbreak spread through the Netherlands. To protect young infants, measles-mumps-rubella (MMR) vaccination was offered to those aged 6-14 months in municipalities with routine first-dose MMR vaccine coverage of <90%. We assessed the tolerability of this early administration of MMR vaccine. METHODS: After study entry (n = 1866), parents of eligible infants (n = 10 097) completed a questionnaire (n = 1304). For infants who received an early MMR vaccine dose (n = 962), we asked for information about adverse events (AEs) associated with the dose. AE frequencies were compared between infants aged 6-8, 9-11, and 12-14 months. Using multivariable logistic regression, we assessed the association between the risk of AEs and age at early MMR vaccination. RESULTS: The response rate was 13%. Parents of 59 infants (6.1%) and 350 infants (36.4%) who received early MMR vaccination reported local and systemic AEs, respectively. Parents of infants vaccinated at 6-8 months of age reported systemic AEs less frequently (32%) than parents of children vaccinated at 9-11 months (45%) and 12-14 months (43%) of age (P= <.001). For local AEs, there were no differences (5%, 7%, and 10%, respectively;P= .08). Compared with vaccination at 6 months, all older infants except those aged 14 months showed an increased risk for any AE and for systemic AEs starting 5-12 days after vaccination. CONCLUSIONS: Early MMR vaccination is well tolerated, with the lowest AE frequencies found in infants aged 6-8 months. It is a safe intervention for protecting young infants against measles.

Disease burden of congenital cytomegalovirus infection at school entry age: study design, participation rate and birth prevalence.

Congenital cytomegalovirus infection (cCMV) may lead to symptoms at birth and long-term consequences. We present a nationwide, retrospective cohort study on the outcome of cCMV up to age 6 years. For this study we identified cCMV, using polymerase chain reaction, by analysing dried blood spots, which are taken shortly after birth for neonatal screening. The group of children with cCMV were compared to a group of children who were cCMV negative at birth. Data were collected about their health and development up to age 6 years. Parents of 73 693 children were invited to participate, and 32 486 (44·1%) gave informed consent for testing of their child's dried blood spot for CMV. Of the 31 484 dried blood spots tested, 156 (0·5%) were positive for cCMV. Of these, four (2·6%) children had been diagnosed with cCMV prior to this study. This unique retrospective nationwide study permits the estimation of long-term sequelae of cCMV up to the age of 6 years. The birth prevalence of cCMV in this study was 0·5%, which is in line with prior estimates. Most (97·4%) children with cCMV had not been diagnosed earlier, indicating under-diagnosis of cCMV.

Performance of a bedside test for tetanus immunity: results of a cross-sectional study among three EDs in the Netherlands in 2012-2013.

INTRODUCTION: Despite sustained high vaccination coverage and a national guideline by the Health Council (HC-guideline) on tetanus postexposure prophylaxis (T-PEP), tetanus sporadically occurs in the Netherlands. This study aims to assess the added value of a bedside test for tetanus immunity (Tetanos Quick Stick (TQS); Ingen BioSciences Group, France), in the context of routine T-PEP in two adult cohorts: those born before introduction of tetanus toxoid vaccination in the National Immunization Programme (NIP) in 1957 (pre-NIP-cohort; n=196) and those born after (NIP-cohort; n=405). METHODS: Adults included at the time of visiting one of three participating EDs received T-PEP as per routine recommendations. Subsequently, a nurse performed the TQS and filled in a questionnaire. We compared the indication for T-PEP based on TQS results with those based on the HC-guideline and with actually administration of T-PEP, stratified by cohort. RESULTS: Among the pre-NIP and NIP-cohort, 16% and 9%, respectively, received T-PEP, while this was not indicated based on the HC-guideline. Furthermore, 8% and 7%, respectively, did not get T-PEP, although it was indicated by the guideline. Comparing the indication derived from the HC-guideline with TQS result found that 22% (pre-NIP-cohort) and 8% (NIP-cohort) were not eligible for T-PEP according to the HC-guideline but had a negative TQS. Conversely, 36% (pre-NIP-cohort) and 73% (NIP-cohort) were eligible for T-PEP according to the HC-guideline but had positive TQS, indicating sufficient tetanus protection. CONCLUSION: Use of the TQS would allow better targeting of T-PEP. Furthermore, stricter adherence to the HC-guideline can prevent overimmunisation and decrease the risk of tetanus.

Bacteraemic and non-bacteraemic/urinary antigen-positive pneumococcal community-acquired pneumonia compared.

The diagnosis of invasive pneumococcal pneumonia is based mainly on bacteraemia. Episodes without bacteraemia, but with a positive urinary antigen test (UAT), are considered non-invasive. We determined differences in outcome between patients with bacteraemic and non-bacteraemic/UAT-positive pneumococcal community-acquired pneumonia (CAP). Adult patients with clinical and radiological evidence of CAP with blood cultures and UAT tests performed at presentation in three Dutch laboratories between June 2008 and May 2010 were included. Clinical characteristics were retrospectively extracted from hospital records. Overall, 168 patients had non-bacteraemic/UAT-positive pneumococcal CAP and 123 had bacteraemic pneumococcal CAP. The day-30 mortality was 9% and 13% for non-bacteraemic/UAT-positive and bacteraemic pneumococcal CAP patients, respectively [risk difference -4%, 95% confidence interval (CI) -11% to +3%, p = 0.28]. In a multivariable logistic regression model, age ≥ 65 years, admission to the intensive care unit/coronary care unit (ICU/CCU) and presence of an immunocompromising condition were associated with day-30 mortality. A non-significant association with mortality was found for bacteraemia [odds ratio (OR) 2.21, 95% CI 0.94-5.21, p = 0.07). No such trend was found for UAT positivity. The median lengths of hospital stay were 8 [interquartile range (IQR) 5-14] and 10 (IQR 6-18) days for non-bacteraemic/UAT-positive and bacteraemic pneumococcal CAP patients, respectively (p = 0.05). As compared to non-bacteraemic/UAT-positive pneumococcal CAP, bacteraemic pneumococcal CAP has a stronger association with day-30 mortality.

Examining a possible association between human papilloma virus (HPV) vaccination and migraine: results of a cohort study in the Netherlands.

UNLABELLED: Since the introduction of the bivalent human papilloma virus (HPV) vaccine in the Netherlands, migraine has been reported as a notable event in the passive safety surveillance system. Research on the association between HPV vaccination and migraine is needed. Therefore, potential migraine cases in 2008-2010 were selected from a group of general practitioners and linked to the vaccination registry. Data were analysed in three ways: (i) incidences of migraine postvaccination (2009/2010) were compared to pre-vaccination incidences (2008); (ii) in a cohort, incidence rates of migraine in vaccinated and unvaccinated girls were compared and (iii) in a self-controlled case series analysis, the relative incidence of migraine in potentially high-risk periods was compared to non-high-risk periods. Incidence rates of migraine for 12- to 16-year-old girls and boys postvaccination were slightly higher than pre-vaccination incidence rates. Incidence rate ratios (IRRs) for vaccinated compared to unvaccinated girls were not statistically significantly higher. Furthermore, the RR for migraine in the high-risk period of 6 weeks following each dose versus non-high-risk period was 4.3 (95% confidence interval (CI) 0.69-26.6) for certain migraine. CONCLUSION: Using different methods, no statistically significant association between HPV vaccination and incident migraine was found. However, the number of cases was low; to definitively exclude the risk, an increased sample size is needed.

Factors affecting the uptake of vaccination by the elderly in Western society.

OBJECTIVE: To present the results of a literature review on factors related to vaccine uptake by elderly persons. METHODS: A systematic literature search was performed using Medline, Embase, and SciSearch to collect all publications available on factors related to vaccine uptake from 1966 until October 2012 for West European and North American societies. In total, 1001 articles were identified and 60 were included in the review. RESULTS: We identified six main themes that influence the willingness to be vaccinated: 1) attitudes and beliefs regarding vaccination in general including positive and negative attitudes and beliefs; 2) perceived risk and severity including knowledge, perceived susceptibility and severity and personal experience; 3) vaccine characteristics including side-effects, effectiveness, content of the vaccine and knowledge; 4) advice and information including influence of the healthcare worker and relatives and the information source and format; 5) general health-related behavior including previous vaccinations, visiting GP or senior center and other preventive behaviors; and 6) accessibility and affordability including logistics, combinations of vaccines and costs. CONCLUSION: The most important factors related to vaccine uptake are people's attitudes and beliefs regarding vaccination (especially their negative attitudes), recommendations of healthcare workers, side effects and effectiveness of the vaccine, and perceived susceptibility.

Pertussis resurgence: waning immunity and pathogen adaptation - two sides of the same coin.

Pertussis or whooping cough has persisted and resurged in the face of vaccination and has become one of the most prevalent vaccine-preventable diseases in Western countries. The high circulation rate of Bordetella pertussis poses a threat to infants that have not been (completely) vaccinated and for whom pertussis is a severe, life-threatening, disease. The increase in pertussis is mainly found in age groups in which immunity has waned and this has resulted in the perception that waning immunity is the main or exclusive cause for the resurgence of pertussis. However, significant changes in B. pertussis populations have been observed after the introduction of vaccinations, suggesting a role for pathogen adaptation in the persistence and resurgence of pertussis. These changes include antigenic divergence with vaccine strains and increased production of pertussis toxin. Antigenic divergence will affect both memory recall and the efficacy of antibodies, while higher levels of pertussis toxin may increase suppression of the innate and acquired immune system. We propose these adaptations of B. pertussis have decreased the period in which pertussis vaccines are effective and thus enhanced the waning of immunity. We plead for a more integrated approach to the pertussis problem which includes the characteristics of the vaccines, the B. pertussis populations and the interaction between the two.

High risk of a large measles outbreak despite 30 years of measles vaccination in The Netherlands.

Our aim was to assess progress towards measles elimination from The Netherlands by studying humoral measles immunity in the Dutch population. A population-based seroepidemiological study was conducted in 2006-2007 (N = 7900). Serum samples were analysed by a bead-based multiplex immunoassay. IgG levels ⩾0·2 IU/ml were considered protective. The overall seroprevalence in the Dutch population was 96%. However, 51% of socio-geographically clustered orthodox Protestant individuals aged <10 years were susceptible. Infants might be susceptible to measles between ages 4 months and 14 months, the age at which maternal antibodies have disappeared and the first measles, mumps, rubella (MMR) vaccination is administered, respectively. Waning of antibody concentrations was slower after the second MMR vaccination than after the first. The Netherlands is at an imminent risk of a measles outbreak in the orthodox Protestant minority. To prevent subsequent transmission to the general population, efforts to protect susceptible age groups are needed.

Increased incidence of serotype-1 invasive pneumococcal disease in young female adults in The Netherlands.

Analysis of the Dutch national invasive pneumococcal disease (IPD) surveillance data by sex reveals an increase in the incidence of serotype-1 disease in young female adults in The Netherlands after the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in the national immunization schedule. This has led to an overall increase in IPD in women aged 20-45 years, which was not observed in men of the same age. No other differences in serotype shifts possibly induced by the introduction of PCV7 were observed between the sexes in this age group. Serotype 1 is a naturally fluctuating serotype in Europe and it has been associated with disease in young healthy adults before. It remains uncertain whether or not there is an association between the observed increase in serotype-1 disease in young female adults and the implementation of PCV7 in The Netherlands.

Immunity against poliomyelitis in the Netherlands, assessed in 2006 to 2007: the importance of completing a vaccination series.

Europe has been declared polio-free since 2002. Here we describe the seroprotection against poliomyelitis in the Dutch population using banked serum samples. Samples from 1,581 inhabitants of eight municipalities with low vaccination coverage (LVC) and an additional 6,386 samples from a nationwide (NS) group (clinical trial number: ISRCTN20164309; collected in 2006­07) were tested for neutralising antibodies (log² reciprocal titres (GMT); non-protection <3) against all three poliomyelitis serotypes. Demographic and epidemiological data were used for statistical regression analysis. Seroprevalence in the NS was 94.6% (type 1), 91.8% (type 2) and 84.0% (type 3). Infants (0­7 months-old) had ≥80% seroprevalence for all serotypes. The highest seroprevalence was found in children, with type 1 and type 2 in five year-olds and type 3 in nine to 10 year-olds. In the LVC group, orthodox protestants, many of whom refuse vaccination, showed seroprevalence rates of 64.9% (type 1), 61.0% (type 2) and 62.1% (type 3). In the NS group, non-Western immigrants and travellers to non-European continents had higher seroprevalences compared to Western immigrants and travellers within Europe, respectively. The Dutch National Immunisation Programme against poliomyelitis has provided good seroprotection, with high and long-lasting GMTs against all serotypes upon completion. The unvaccinated population remains at risk.

COVID-19 vaccination-induced antibody responses and waning by age and comorbidity status in a large population-based prospective cohort study.

BACKGROUND: Information on the magnitude and duration of antibody levels after COVID-19 vaccination in different groups may be useful for prioritizing of additional vaccinations. METHODS: Serum samples were collected every six months in a prospective cohort study among adults in the Netherlands. Geometric mean concentrations (GMCs) of antibodies against the receptor binding domain of the SARS-CoV-2 spike protein were calculated after the primary series, first, and second booster vaccinations. Effects of age (18-59 vs 60-85 years) and medical risk conditions on GMC 2-6 weeks and 21-25 weeks after each vaccination, and on waning during 3-25 weeks after each vaccination, were estimated by linear regression. RESULTS: We included 20,640, 15,229 and 8,392 samples collected after primary, first and second booster vaccination, respectively. GMCs at 2-6 and 21-25 weeks after primary series were lower in participants with older age or medical risk conditions. After the first booster, older age was associated with lower GMC at 2-6 weeks and at 21-25 weeks. Waning after the first and second boosters (only 60-85) was not associated with age or medical risk conditions. CONCLUSIONS: Since antibody differences by age and medical risk groups have become small with increasing number of doses, other factors such as COVID-19 disease severity rather than antibody levels are useful for prioritization of additional vaccinations.

Incidence of multiple sclerosis in the general population in the Netherlands, 1996-2008.

BACKGROUND: We estimated the multiple sclerosis (MS) incidence in the Netherlands for better active monitoring of potential vaccine safety signals. METHODS: A retrospective cohort study (1996-2008) was conducted using a population-based general practice research database containing electronic medical records. Additional information was collected to validate incident probable cases. RESULTS: In the source population (648,656 persons), 146 incident probable MS cases were identified. Overall incidence rate was 6.3/100,000 person years (py; 95% CI, 5.2-7.2). In the subgroup in which MS could be fully validated, the incidence increased from 4/100,000 py (95% CI, 3-5) in 1996-2004 to 9/100,000 py in 2007/8 (95% CI, 6-16). This increase was highest among women, but not statistically significantly different by gender. The median lag time between first recorded symptoms and MS diagnosis decreased from 32 months (<1998) to 2 months (>2005). CONCLUSIONS: MS is rare in the Netherlands. In recent years, there was a slight increase in the incidence especially among women during the fertile age. This increase coincided with a decrease in lag time between symptoms and diagnosis, both for men and women. This trend should be taken into account in the interpretation of MS cases occurring in a population where new vaccinations will be introduced shortly.

Prevalence of hepatitis B virus infection in The Netherlands in 1996 and 2007.

We aimed to assess differences in the prevalence of hepatitis B virus (HBV) infection in The Netherlands between 1996 and 2007, and to identify risk factors for HBV infection in 2007. Representative samples of the Dutch population in 1996 and 2007 were tested for antibodies to hepatitis B core antigen (anti-HBc), hepatitis B surface antigen (HBsAg) and HBV-DNA. In 2007, the weighted anti-HBc prevalence was 3·5% (95% CI 2·2-5·5) and the HBsAg prevalence was 0·2% (95% CI 0·1-0·4). In indigenous Dutch participants, the anti-HBc prevalence was lower in 2007 than in 1996 (P=0·06). First-generation migrants (FGMs) had a 13-fold greater risk of being HBsAg- and/or HBV-DNA-positive than indigenous Dutch participants. In indigenous Dutch participants, risk factors for anti-HBc positivity were older age and having received a blood product before 1990. In FGMs, being of Asian origin was a risk factor. In second-generation migrants, having a foreign-born partner and injecting drug use were risk factors. FGMs are the main target group for secondary HBV prevention in The Netherlands.