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.

[The control of pertussis after half a century of vaccination]. / De bestrijding van kinkhoest na een halve eeuw vaccineren.

Notification of laboratory-confirmed pertussis is mandatory in the Netherlands. Thus, the public health service can see to it that timely chemoprophylaxis (within 3 weeks after the onset of symptoms in the index case) is prescribed for all members of the household, should there be a vulnerable non-vaccinated or insufficiently vaccinated newborn in the family. However, it was shown that the delay in this notification was so long that intervention by the prescription of chemoprophylaxis could take place in time to protect a newborn infant in only 10% of the cases. The effectiveness of the notification system in facilitating timely chemoprophylaxis is therefore questioned and it is concluded that other ways to achieve such intervention, independent of notification, are needed. Doctors should always ascertain the presence of a newborn infant in the household of pertussis patients and consider chemoprophylaxis immediately, even ahead of notification. Even if not in time for effective prophylaxis, mandatory notification is still of utmost importance for the evaluation of pertussis immunisation. Surveillance data obtained from notification are used in scenario analysis and contribute to the underpinning of alternative immunisation policies. After all, major improvements in pertussis control can be expected from the addition of (re)vaccination of other target groups, such as mothers of newborns, adolescents or adults, to the national immunisation programme.

[Adverse events following influenza vaccination: reaction to specific reports and the necessity of a central registration system]. / Bijwerkingen na influenzavaccinatie: reactie op enkele incidenten en het belang van centrale registratie.

The influenza vaccine is considered safe, but information on vaccine-related adverse events is limited and a nationwide overview of adverse events is lacking. In 2006, after deaths occurred in Israel and the Netherlands following influenza vaccination, the Dutch Ministry of Health, Welfare and Sport (VWS) asked the National Institute for Public Health and the Environment (RIVM) twice for a recommendation regarding the continuation of the national vaccination campaign. After 4 deaths were reported in Israel in October 2006 following administration of Vaxigrip, the Dutch vaccination campaign was suspended for one week. One month later, 4 additional deaths were reported after influenza vaccination in the Netherlands. The newly appointed outbreak management team concluded that a causal relationship between vaccination and the deaths was highly unlikely, based on data regarding the individual cases, background mortality rates and prior reports of adverse events. Further suspension of the vaccination campaign was deemed unnecessary this time. A centralised nationwide registry of adverse events has since been established to provide further insight into the incidence of adverse events following influenza vaccination. Physicians are advised to report potential adverse events following influenza vaccination to the Netherlands Pharmacovigilance Centre Lareb (www.lareb.nl).

Public health implications of using various case definitions in The Netherlands during the worldwide SARS outbreak.

This study analysed the consequences of deviation from the WHO case definition for the assessment of patients with suspected severe acute respiratory syndrome (SARS) in The Netherlands during 2003. Between 17 March and 7 July 2003, as a result of dilemmas in balancing sensitivity and specificity, five different case definitions were used. The patients referred for SARS assessment were analysed from a public health perspective. None of the patients referred had SARS, based on serological and virological criteria. Nevertheless, all 72 patients required thorough assessment and, depending on the results of the assessment, institution of appropriate prevention and control measures. Changing case definitions caused confusion in classifying cases. A centralised assessment of the reported cases by a team with clinical and public health expertise (epidemiological and geographical risk assessment) is a practical solution for addressing differences in applying case definitions. The burden of managing non-cases is an important issue when allocating public health resources, and should be taken into account during the preparation phase, rather than during an outbreak. This applies not only to SARS, but also to other public health threats, such as pandemic influenza or a bioterrorist episode.

Meningococcal carriage in relation to an outbreak of invasive disease due to Neisseria meningitidis serogroup C in the Netherlands.

BACKGROUND: a cross-sectional study on meningococcal carriage was performed in Putten, a small rural town in the Netherlands where an unusual high incidence of invasive meningococcal disease (IMD) due to Neisseria meningitidis C:2a:P1.5 occurred. The outbreak was controlled by mass vaccination of all inhabitants aged 2 to 20 years. METHODS: meningococcal carriage was studied in three groups: (1) a systematic age-specific sample of 2-20 year olds who visited the immunization clinic in Putten (January 1998: n=411); (2) children and adolescents in the same age range recruited through a kindergarten and schools in Venlo, a town where the causative strain of IMD had not been encountered (February 1998; n=374); (3) all initial carriers in Putten and a sample of non-carriers in that town (March 1998: n=145). Oropharyngeal swabs were taken for the purpose of isolating N. menigitidis. RESULTS: the prevalence of carriage was 12.4% in Putten and 18.2%, in Venlo, but the prevalence of group C meningococci was higher in Putten (1.7%) than Venlo (0.5%). N. meningitidis C:2a:P1.5 was isolated twice in Putten and not at all in Venlo. A second examination in Putten showed that 18 of the 22 repeatedly tested carriers were still carriers, and six new carriers were found among the 55 initial non-carriers. Of the two known carriers of C:2a:P1.5, one was still carrying the same strain, and the other did not participate in the second investigation. Carriage was associated with increasing family size, discotheque visits and visits to youth clubs and sports clubs. In contrast, visits to the swimming pool appeared to be related to a lower risk, as was recent antibiotic use. CONCLUSION: the prevalence of carriage with the invasive strain C:2a:P1.5 was low in the population that experienced a community-wide outbreak recently: the specific strain was not found in the reference population. This indicates a relatively high risk of developing the invasive disease for those who become infected with such strains.

Descriptive epidemiology of exanthems in the Rotterdam region January 1997 to June 1998.

The European Advisory Group on Immunisation has recommended that measles should be eliminated from Europe by the year 2007, a target accepted by National Immunisation Programme Managers for the World Health Organization (WHO) European Region countries. I

The incidence of pertussis in the Netherlands has remained high since an outbreak occurred in 1996.

The incidence of pertussis throughout the Netherlands, determined by notifications, rose suddenly in 1996 to reach 27.2 cases per 100 000 population, compared with 2.3/100 000 on average from 1989 to 1995. Earlier increases in 1989-1990 and 1994 reflected

Programme for preventing perinatal hepatitis B infection through screening of pregnant women and immunisation of infants of infected mothers in The Netherlands, 1989-92. National Hepatitis B Steering Committee.

OBJECTIVES: To launch a programme for the prevention of perinatal infection with hepatitis B in the Netherlands. DESIGN: Routine antenatal screening and intervention programme. SETTING: Community antenatal programme, the Netherlands. SUBJECTS: Infants of mothers who were carriers of hepatitis B detected by routine screening. INTERVENTIONS: Infants of infected mothers received hepatitis B immunoglobulin at birth and four doses of hepatitis B vaccine in conjunction with routine immunisation at 3, 4, 5, and 11 months of age. MAIN OUTCOME MEASURES: Results of screening and immunisation from 1989-92. RESULTS: The coverage of screening increased from 46% in 1989 to 84% in 1992. Hepatitis B surface antigen was detected in 2145 women (0.44%). The coverage of postnatal immunoprophylaxis in 1645 neonates born to mothers who were carriers of hepatitis B was 85% (1391); in 3% (42) there was a delay in administration of immunoglobulin of over 24 hours. In 1991, 96% (537), 95% (532), 94% (525), and 87% (489) of the infants received the first, second, third, and fourth dose of vaccine, respectively. There was considerable variation in the timing of vaccination; 17% (258) of the infants received their first dose more than two weeks late. Of the 59% (583) of infants who received the fourth dose more than two weeks beyond target age, 14% (141) also received their first dose too late. CONCLUSIONS: A prevention programme for perinatal hepatitis B in an area of low prevalence, when incorporated into existing health care, is feasible and achieves satisfactory coverage rates. Intensive follow up is needed to improve adherence to the immunisation schedule.

[Measles in The Netherlands; epidemiology and the effect of vaccination]. / Mazelen in Nederland; epidemiologie en de invloed van vaccinatie.

OBJECTIVE: To estimate the incidence of measles in the Netherlands and assess the effect of vaccination with regard to vaccination status. DESIGN: Retrospective study. METHOD: Data were collected from the Central Bureau for Statistics (CBS), reported cases at the National Health Department (NHD), data from hospitals concerning admissions, morbidity data from the General Practitioner Networks, serological data from virology laboratories and serological data from several other studies. RESULTS: After introduction of the measles vaccination in 1976, morbidity and reported cases decreased dramatically. Some data suggest that measles in children over 10 years old are reported more frequently. Death caused by measles did not occur after 1988. CONCLUSION: The massive vaccination since 1976 resulted in an initial decrease in incidence of measles. The increase in incidence thereafter was probably caused by an increase in, and crowding of vulnerable, older people. No effect on the severity of the complications were seen so far. Surveillance is necessary to follow groups at risk and to take proper preventive measures.

[Pediatric surveillance of invasive infections caused by Haemophilus influenzae type b in children in the period following introduction of vaccination]. / Pediatrische surveillance van invasieve infecties door Haemophilus influenzae type b bij kinderen in de periode na introductie van de vaccinatie.

OBJECTIVE: Evaluation of the effect of vaccination against Haemophilus influenzae type b (Hib) on the occurrence of invasive Hib infections in children since its introduction into the national immunization programme in April 1993. DESIGN: Observational study. SETTING: Nationwide investigation. METHOD: Data collected through active surveillance of invasive Hib infections by paediatricians for the period from October 1993 to September 1994 (11 months) were compared with data from the meningitis surveillance by the Netherlands Reference Laboratory for Bacterial Meningitis. RESULTS: A total of 139 paediatric reports of invasive disease by H. influenzae concerned 57 cases of only meningitis, 35 of meningitis with sepsis, 2 of meningitis with arthritis, one of meningitis with arthritis and osteomyelitis, 34 of epiglottitis including one case with sepsis, 8 of only sepsis and 2 of only arthritis. All proven infections by Hib occurred in children who had not or incompletely been vaccinated. One child with sepsis had had three vaccinations and became ill five months later; the isolated bacterial strain was not serotyped. Typing was performed in only 80% of the isolates, of which 98% were of type b. Appropriate culturing and typing was often omitted in case of epiglottitis. CONCLUSION: The effect of vaccination against Hib became apparent in a small number of cases of invasive Hib disease reported by paediatricians; the peak incidence of meningitis no longer occurred in children under one year of age but in children aged one year. The paediatric surveillance described offers possibilities for monitoring Hib epidemiology.

[Significant decline of the number of invasive Haemophilus influenzae infections in the first 4 years after introduction of vaccination against H. influenzae type B in children]. / Sterke daling van het aantal invasieve infecties door Haemophilus influenzae in de eerste 4 jaar na de introductie van de vaccinatie van kinderen tegen H. influenzae type b.

OBJECTIVE: To evaluate the effect of four years of immunisation against Haemophilus influenzae type b (Hib) on the occurrence of invasive H. influenzae infection and of vaccine failure in children. DESIGN: Descriptive. METHOD: Through the Nederlands Signalerings-Centrum Kindergeneeskunde (NSCK; Dutch Paediatric Surveillance Unit), invasive H. influenzae infections in children under 15 years of age reported by paediatricians were registered from October 1993 until December 1997. On the basis of the NSCK data the incidence of invasive H. influenzae infections was determined for 1994-1997 in relation to the children's age. RESULTS: The numbers of cases of invasive H. influenzae infection were 129 in 1994, 41 in 1995, 24 in 1996 and 8 in 1997. The decrease mainly concerned type b infections. The mean age at infection increased in the first two years after the introduction of vaccination. No apparent change in the clinical presentation of infection was observed. In four years of surveillance a total of nine cases of vaccine failure was reported. CONCLUSION: The progressive effect of vaccination against Hib was reflected in the strong decline of the number of invasive Hib infections, mainly in the youngest children. In accordance with the high level of voluntary vaccination in the Netherlands (95.5% as of January 1st 1997) and the expected high vaccine efficacy the number of vaccine failures was low. A further beneficial effect for the youngest children may be expected from starting the vaccination scheme at a still earlier age.

[Evaluation of the hepatitis B prevention program in newborn infants. I. National data, 1990]. / Evaluatie van het hepatitis B-preventieprogramma bij pasgeborenen. I. Landelijke gegevens, 1990.

OBJECTIVE: To evaluate the effectiveness of the national programme for prevention of perinatal hepatitis B infections. SETTING: The regional public health laboratories and provincial immunization administrations in the Netherlands. DESIGN: Retrospective evaluation. METHODS: Starting October 1989 routine screening of pregnant women for HBsAg was performed and passive-active immunisation of infants of HBsAg-positive mothers was added to the national immunisation programme. Infants receive hepatitis B immunoglobulin at birth and hepatitis B vaccine at 3,4,5, and 11 months of age, concomitant with the DTP-polio vaccine. The effectiveness of screening and intervention in 1990 was evaluated. RESULTS: Screening covered about 85% of the pregnant population and the prevalence (0.44%) was less than expected. About 60% of the infants born to HBsAg-positive mothers were registered for vaccination. Of these infants the average coverage was 83% for immunoglobulin, and 90%, 86%, 80% and 55% for the four successive hepatitis B vaccinations. There was considerable delay in vaccine administration; frequently doses were administered later than recommended. CONCLUSION: Compliance with screening and vaccination appeared incomplete. Recommendations for the simplification of the current programme are made.

[Whooping cough in The Netherlands, 1989-1994]. / Kinkhoest in Nederland, 1989-1994.

OBJECTIVE: To obtain insight into the present incidence of pertussis. DESIGN: Observational study of data from different sources of surveillance. METHOD: For the years 1989-1994 the incidence of pertussis was estimated from the number of pertussis notifications, from laboratory data or serodiagnosis, from isolations of Bordetella and from the national registration of clinical diagnosis of hospital admissions. RESULTS: The numbers of notifications and positive serology yielded similar average yearly incidences for the period 1989-1994 (2.4 and 2.3/100.000 respectively). According to notifications and positive serodiagnosis, respectively, peak incidences occurred in 1989 (3.5 and 2.4/100.000) and 1994 (4.2 and 4.1/100.000). In 1993 the incidence of positive serodiagnosis (3.2 per 100.000) was also higher than in the other years. The incidence based on hospitalizations, notifications and positive serology was highest among children under 1 year of age. In the period 1989-1993 no deaths were recorded. The vaccine efficacy amounted to 91%. CONCLUSION: For 1989-1994 the pattern over time was mostly consistent with pertussis being an endemic disease in childhood with 4-yearly peaks. The incidence of hospitalizations emphasized the seriousness of the illness in infants. It is important that general practitioners are on the alert for the occurrence of pertussis in vaccinated and unvaccinated children and adults.

[Measles epidemic in the Netherlands, 1999-2000]. / Mazelenepidemie in Nederland, 1999-2000.

OBJECTIVE: Description of measles epidemic in the Netherlands, 1999-2000. DESIGN: Observational descriptive study. METHODS: Intensified surveillance of measles cases by means of a case register established at the 'Landelijke Coördinatiestructuur Infectieziektebestrijding (LCI)' [National Co-ordination Centre for Communicable Disease Outbreak Management]. RESULTS: There were 3,292 reported measles patients, most of whom came from areas with low vaccine coverage. Of these patients, 94% had not been vaccinated; in 85% of cases this was for religious reasons. Of the 158 (5%) vaccinated patients, 157 had not (yet) received a second dose of vaccine. The incidence of measles increased with decreasing vaccine coverage in a municipality, both for unvaccinated and vaccinated persons. Three of the reported patients died. The percentage of patients with one or more complications was 22% in the group < 15 months of age, 19% in the group 15 months-4 years, 16% in the group 5-9 years, 11% in the group 10-19 years, and 15% in the group > 19 years of age. CONCLUSION: Considering the complications observed, the epidemic described involved a serious disease. Vaccination was accompanied by effective protection against measles infection and its complications. Herd immunity outside the unvaccinated groups was sufficient to prevent an epidemic there. However, incidental spread to vaccinated children did occur; the greatest risk factor for acquiring measles for vaccinated children is a stay in an area with low vaccine coverage.

[Congenital toxoplasmosis]. / Congenitale toxoplasmose.

Congenital toxoplasmosis is characterized by the classical triads: hydrocephaly, chorioretinitis and intracerebral calcifications. In fact it is an uncommon manifestation of congenital infection with the parasite Toxoplasma gondii, that is generally subclinical in the neonatal period. But there is a substantial risk of delayed clinical manifestation due to exacerbation of infection: chorioretinitis with loss of vision. With some case histories the interpretation of serodiagnostic techniques is explained and the necessity of repeated tests up to the age of one year in order to exclude a congenital infection definitely, is emphasized.