Susan Hahné

Effectiveness of antibiotics in preventing meningococcal disease after a case: systematic review

Objective To summarise the evidence for the role of antibiotics in preventing further cases of meningococcal disease through chemoprophylaxis given to the index patient, household contacts, and children in day care settings after a single case. Design Systematic review. Methods Studies were identified by searching Embase (1983-2003), Medline (1965-2003), and CAB Health (1973-2003) and by contacting the World Health Organization and the European meningococcal disease surveillance network and examining references of identified papers. The review included all studies with at least 10 cases in which outcomes were compared between treated and untreated groups. Main outcome measure Subsequent cases of meningococcal disease 1-30 days after onset of disease in the index patient. Results Four observational studies and one small trial met the inclusion criteria. Meta-analysis of studies on chemoprophylaxis given to household contacts showed a significant reduction in risk (risk ratio 0.11, 95% confidence interval 0.02 to 0.58). The number needed to treat to prevent a case was estimated as 218 (121 to 1135). Primary outcome data were not available in studies of chemoprophylaxis given to the index patient: when prophylaxis had not been given, rate of carriage after discharge from hospital was estimated as 3% (0 to 6), probably an underestimate of the true rate. No studies of chemoprophylaxis in day care settings were identified that met the inclusion criteria. Conclusion There have been no high quality experimental trials looking at control policies for meningococcal disease. The best available evidence is from retrospective studies. The risk of meningococcal disease in household contacts of a patient can be reduced by an estimated 89% if they take antibiotics known to eradicate meningococcal carriage. Chemoprophylaxis should be recommended for the index patient and all household contacts.

Large ongoing measles outbreak in a religious community in the Netherlands since May 2013

Despite vaccination coverage over 95%, a measles outbreak started in May 2013 in the Netherlands. As of 28 August, there were 1,226 reported cases, including 82 hospitalisations. It is anticipated that the outbreak will continue. Most cases were orthodox Protestants (n=1,087/1,186; 91.7%) and unvaccinated (n=1,174/1,217; 96.5%). A unique outbreak control intervention was implemented: a personal invitation for measles-mumps-rubella (MMR) vaccination was sent for all children aged 6–14 months living in municipalities with MMR vaccination coverage below 90%.

Mumps outbreak among vaccinated university students associated with a large party, The Netherlands, 2010

We investigated a mumps outbreak within a highly vaccinated university student population in the Netherlands by conducting a retrospective cohort study among members of university societies in Delft, Leiden and Utrecht. We used an online questionnaire asking for demographic information, potential behavioural risk factors for mumps and the occurrence of mumps. Vaccine status from the national vaccination register was used. Overall, 989 students participated (20% response rate). Registered vaccination status was available for 776 individuals, of whom 760 (98%) had been vaccinated at least once and 729 (94%) at least twice. The mumps attack rate (AR) was 13.2% (95%CI 11.1-15.5%). Attending a large student party, being unvaccinated and living with more than 15 housemates were independently associated with mumps ((RR 42 (95%CI 10.1-172.4); 3.1 (95%CI 1.7-5.6) and 1.8 (95%CI 1.1-3.1), respectively). The adjusted VE estimate for two doses of MMR was 68% (95%CI 41-82%). We did not identify additional risk factors for mumps among party attendees. The most likely cause of this outbreak was intense social mixing during the party and the dense communal living environment of the students. High coverage of MMR vaccination in childhood did not prevent an outbreak of mumps in this student population.

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.

Hepatitis B vaccination targeted at behavioural risk groups in the Netherlands: does it work?

In November 2002, the Netherlands adopted a vaccination program targeted at behavioural risk groups. Between January 2003 and December 2007, 1386 patients acutely infected with HBV were reported. Reported cases declined from 326 in 2003 to 220 in 2007. Sexual intercourse was the most frequently reported mode of transmission (65%), especially among men having sex with men. Genotypes A and D remained predominant. In total, 40,600 participants were fully vaccinated, the overall compliance was 62%, and the estimated overall program coverage was 12% of the at-risk population. With more effort, more susceptibles may be reached, but the program will not be sufficient to substantially reduce HBV in the Netherlands. Therefore, universal vaccination should be considered.

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.

Exceptionally low rotavirus incidence in the Netherlands in 2013/14 in the absence of rotavirus vaccination

An unexpected drop in rotavirus (RV) detections was observed in the Netherlands in 2014, without RV vaccination. The estimated decrease in RV detections and gastroenteritis consultations in under five year-olds, in January-April 2014, compared to the same months in previous years, was 72% and 36%, respectively. The low birth rate, mild winter, high RV incidence in the previous year and the introduction of RV vaccination in neighbouring countries may have contributed to this decrease.

Persistent and transient hepatitis B virus (HBV) infections in children born to HBV-infected mothers despite active and passive vaccination.

Summary.  Combined passive and active immunization for newborns very effectively prevents perinatal hepatitis B virus (HBV) infections. In the Netherlands, babies born to hepatitis B surface antigen (HBsAg)‐positive women receive passive immunization with hepatitis B and at least three active HBsAg vaccinations. Serological testing for the presence of HBV markers was offered for all infants born to HBsAg‐positive mothers between January 2003 and July 2007, after completion of their vaccination schedule. About 75% of the infants (n = 1743) completed their HB‐vaccination schedule and participated in the serologic evaluation. Twelve of them (0.7%) were found to be HBV infected. Furthermore, we identified three older children with high levels of anti‐HBc, anti‐HBs and anti‐HBe, while they were HBsAg and HBV DNA negative. This serologic profile is evidence for a resolved HBV infection. In the group of older children (1.5–5 years of age, n = 728), about half of the HBV‐infected children (3 of 7) had already cleared their infection at the time of sampling. For a proper evaluation of the efficacy of a new intervention programme to prevent vertical HBV transmission, it is also important to analyse the HBV markers in serum collected when the children are older than 1.5 years. In a programmatic setting, all children born to HBV‐infected mothers should be tested not only for the level of anti‐HBs but also for the absence of HBsAg, because 2 of the 12 HBV‐infected children (17%) had a high level of anti‐HBs.

Air travel as a risk factor for introduction of measles in a highly vaccinated population

Epidemiological and molecular investigation of two small measles clusters in The Netherlands in July/August 2007 revealed an association with travel by air of the index cases and nosocomial spread in the first cluster. Although these importations did not result in an outbreak among unvaccinated subjects, the observations illustrate the challenges for measles control in a country with high measles vaccination coverage (> 95%) but with pockets of low coverage.

Hepatitis B vaccination of men who have sex with men in the Netherlands: should we vaccinate more men, younger men or high-risk men?

Objectives The selective vaccination programme against hepatitis B virus (HBV) was introduced in the Netherlands in 2002 targeting high-risk groups, including men who have sex with men (MSM). Despite the high average age of vaccination in MSM, the number of notifications of acute HBV recently declined. We investigate whether this can be attributed to the selective vaccination programme. We examine how vaccination strategies could be improved and the impact of universal infant vaccination introduced in 2011. Methods We use a mathematical model for HBV transmission among MSM. The incidence of HBV was calculated from the model and from notification data of acute HBV. Results A decline was observed in the incidence of HBV since 2006, as calculated from the model; this decline was smaller than that observed in data if all MSM were equally likely to be vaccinated. Assuming that high-risk MSM were more likely to be vaccinated than low-risk MSM resulted in a steeper decline in modelled incidence and better agreement with observed incidence. Vaccinating MSM at a younger age or doubling the vaccination rate would increase the impact of selective vaccination, but is less effective than vaccinating high-risk MSM. Conclusions Selective HBV vaccination of MSM in the Netherlands has had a substantial impact in reducing HBV incidence. The reduction suggests that vaccination rates among high-risk MSM were higher than those among low-risk MSM. Countries that have not yet reached 35-year cohorts with universal childhood vaccination should actively implement or continue selective high-risk MSM vaccination.