Seroepidemiology of diphtheria, tetanus, poliomyelitis and pertussis : evaluation of the national immunisation programme in the Netherlands

In view of the evaluation of the National Immunisation Programme in the Netherlands the main objectives were to obtain insight into the immunity to diphtheria, tetanus and poliomyelitis, into the occurrence of pertussis and to improve serodiagnosis of pertussis.In a population-based nationwide sampling, 8359 sera (response 55%) were collected, and to gain access to orthodox reformed individuals refusing vaccination, in a sample from municipalities with low vaccine coverage 1589 sera (response 52.5%). In the nationwide sample, the prevalence of diphtheria and tetanus antibodies (≥0.01 IU/ml in toxin inhibition assay) was 88% and 84%, resp. In at least 90% antibodies (titre≥1:8 in neutralisation assay) against poliovirus types 1, 2 and 3 were measured. For those born after mass vaccination was introduced (&lt;45 years) the prevalence of antibodies to diphtheria, tetanus, poliovirus types 1 and 2 was at least 92.5% and for poliovirus type 3 at least 80%. Diphtheria and tetanus antibodies decreased with age for those born before vaccination was introduced (≥45 years). Only 40% of orthodox reformed individuals had diphtheria and 60% had tetanus antibodies. Less than 70% had poliovirus type 1, 2 and/or 3 antibodies. We concluded that the Dutch immunisation programme induced long-term diphtheria, tetanus and poliomyelitis immunity. While adults are very well protected against poliomyelitis, a great number of adults lack diphtheria or tetanus antitoxin antibodies. These adults might benefit from diphtheria (re)vaccination; however, offering a primary tetanus vaccination to cohorts born before the introduction of vaccination would probably be more effective than routine revaccination. Introduction of C. diphtheriae or poliovirus in socio-geographically clustered orthodox reformed groups might constitute a danger of spread of these pathogens.Pertussis surveillance data from notifications, positive serology and hospital admissions (1976-98) showed a sudden increase in the number of pertussis cases in 1996-97. According to notifications and serology data, the increase among, mostly unvaccinated, children less than 1 year was similar to the increase in hospital admissions. For older, mostly vaccinated, individuals the increase in hospital admissions was relatively small. The increase of reported vaccinated patients of all ages was higher than for unvaccinated patients. We postulated that the proportion of pertussis infections resulting in recognizable symptoms has increased among vaccinated individuals due to a mismatch of the vaccine strain and circulating B. pertussis strains.To investigate at which level IgG antibodies against pertussis toxin (IgG-PT) in a single serum sample are indicative for recent pertussis, IgG-PT was analysed in 7756 population-based sera, in sera of 3491 patients with at least a fourfold IgG-PT increase, in paired sera of 89 patients with positive cultures or polymerase chain reactions and in sera of 57 pertussis patients with a median follow-up of 1.4 years. IgG-PT levels of at least 100 U/ml were present in less than 1% of the population, are reached by most pertussis patients within 4 weeks after disease onset and persist only temporarily. We concluded that such levels are diagnostic for recent or actual infection with B. pertussis .Our results not only show that childhood vaccination should be sustained, but that adult vaccination could be considered. We have to anticipate long-term effects of mass vaccination, such as gaps in immunity as a result of decreased circulation of the pathogens and waning immunity. Epidemiological studies directed towards evaluation of vaccination should continue to provide a scientific basis for vaccination strategy.</p

Estimation of age-specific rates of reactivation and immune boosting of the varicella zoster virus

Studies into the impact of vaccination against the varicella zoster virus (VZV) have increasingly focused on herpes zoster (HZ), which is believed to be increasing in vaccinated populations with decreasing infection pressure. This idea can be traced back to Hope-Simpson's hypothesis, in which a person's immune status determines the likelihood that he/she will develop HZ. Immunity decreases over time, and can be boosted by contact with a person experiencing varicella (exogenous boosting) or by a reactivation attempt of the virus (endogenous boosting). Here we use transmission models to estimate age-specific rates of reactivation and immune boosting, exogenous as well as endogenous, using zoster incidence data from the Netherlands (2002–2011, n = 7026). The boosting and reactivation rates are estimated with splines, enabling these quantities to be optimally informed by the data. The analyses show that models with high levels of exogenous boosting and estimated or zero endogenous boosting, constant rate of loss of immunity, and reactivation rate increasing with age (to more than 5% per year in the elderly) give the best fit to the data. Estimates of the rates of immune boosting and reactivation are strongly correlated. This has important implications as these parameters determine the fraction of the population with waned immunity. We conclude that independent evidence on rates of immune boosting and reactivation in persons with waned immunity are needed to robustly predict the impact of varicella vaccination on the incidence of HZ.PIENTER2 serological stud

Diphtheria antitoxin levels in the Netherlands: a population-based study.

In a population-based study in the Netherlands, diphtheria antitoxin antibodies were measured with a toxin-binding inhibition assay in 9, 134 sera from the general population and religious communities refusing vaccination. The Dutch immunization program appears to induce long-term protection against diphtheria. However, a substantial number of adults born before the program was introduced had no protective diphtheria antibody levels. Although herd immunity seems adequate, long-term population protection cannot be assured. As more than 60% of orthodox reformed persons have antibody levels lower than 0.01 IU/ml, introduction of diphtheria into religious communities refusing vaccination may constitute a danger of spread of the bacterium

Reemergence of pertussis in the highly vaccinated population of the Netherlands: observations on surveillance data.

We analyzed pertussis reporting, death, hospitalization, and serodiagnostic data from 1976 to 1998 to help explain the cause of the 1996 pertussis outbreak in the Netherlands. The unexpected outbreak was detected by an increase in pertussis reporting and by other surveillance methods. In 1996, according to reporting and serologic data, the increase in pertussis incidence among (mostly unvaccinated) children less than 1 year of age was similar to the increase in hospital admissions. Among older (mostly vaccinated) persons, the increase in hospital admissions was relatively small. The increase in pertussis incidence was higher among vaccinated than among unvaccinated persons of all ages. This resulted in lower estimates of vaccine effectiveness. The proportion of pertussis infections resulting in recognizable symptoms may have increased among vaccinated persons because of a mismatch of the vaccine strain and circulating Bordetella pertussis strains. The small immunogenicity profile of the Dutch vaccine may have resulted in greater vulnerability to antigenic changes in B. pertussis

Pertussis in The Netherlands: an outbreak despite high levels of immunization with whole-cell vaccine.

In 1996, a sudden increase in pertussis incidence was reported in the Netherlands (2.1 per 100,000 in 1995, 18 per 100,000 in 1996). Although not all potential surveillance artifacts could be excluded, it is highly probable that the data reflect a true outbreak. However, the cause of this increase has not yet been determined. Further research is directed to the severity of disease and a possible mismatch between the vaccine and the circulating Bordetella strains

Hospitalization due to varicella in the Netherlands

<p>Abstract</p> <p>Background</p> <p>In the Netherlands, incidence of physician's consultations and hospitalizations for varicella is low compared to other countries. Better knowledge about the severity of varicella among Dutch hospitalized patients is needed. Therefore, a medical record research was conducted among hospitalized patients with diagnosis varicella.</p> <p>Methods</p> <p>Hospital admissions due to varicella in 2003-2006 were obtained from the National Medical Register. Retrospectively, additional data were retrieved from the medical record of patients hospitalized with varicella in 23 Dutch hospitals using a standardized form. Analyses were performed using descriptive statistics.</p> <p>Results</p> <p>The study population (N = 296) was representative for all varicella admissions in the Netherlands (N = 1,658) regarding age, sex, duration of admission and type of diagnosis. Complications were recorded in 76% of the patients (37% had at least one relatively severe complication). Bacterial super infections of skin lesions (28%), (imminent) dehydration (19%), febrile convulsions (7%), pneumonia (7%) and gastroenteritis (7%) were most frequently reported. No varicella-related death occurred within the study population and 3% of the patients had serious rest symptoms.</p> <p>Conclusions</p> <p>It is not likely that the severity of varicella among hospitalized patients in the Netherlands differs from other countries. A considerable part of the varicella complications among hospitalized patients was rather moderate and can be treated effectively, although in a third of the hospitalized cases with complications, severe complications occurred. These data are relevant in the decision-making process regarding whether or not to introduce routine varicella vaccination in the Netherlands.</p