Two doses of pandemic influenza A(H1N1) vaccine: tolerability in healthy young children in the Netherlands.

During the 2009 influenza pandemic, children aged 6 months up to and including 4 years, without chronic illness, were vaccinated with two doses of Pandemrix(®) through mass vaccination in the Netherlands. During the vaccination campaign a warning was issued about fever after the second dose of Pandemrix(®). Therefore, we investigated the tolerability of both doses Pandemrix(®) in these children. Among parents of children eligible for vaccination, 1500 questionnaires were distributed during both, the first and second mass vaccination session. We asked for the occurrence, time interval, and duration of local reactions and systemic adverse events (AEs). The responses were 36.7% and 29.5% after each dose, respectively. Local reactions were reported in 40.4% and 39.3%, most frequently, pain at the injection site. After the first and second dose, 29.6% and 30.7% of all children experienced fever (mean temperature 38.8{degree sign}C). Other systemic AEs were reported in 41.6% and 42.9% of the children. No differences were seen between the first and second dose for all reported AEs except for pallor. One child was hospitalized after the first dose, but a causal relation to the vaccination was considered improbable. In conclusion, fever was frequently reported in children 6 months up to and including 4 years of age after the first and second dose of Pandemrix(®). However, for almost all AEs, including fever, no dose effect was observed. Reported AEs were mostly mild and all were transient.

Discolored leg syndrome after vaccination--descriptive epidemiology.

Discoloration of the leg following vaccination is a relatively unknown entity. We carried out a study of discolored leg syndrome (DLS) during a 10-year consecutive period with the objective of characterizing DLS in infants following vaccination received in the Dutch National Vaccination Program as well as its occurrence and association with different vaccines. Discolored leg syndrome was defined as an even or patchy red, blue or purple discoloration of the leg(s) and/or leg petechiae with or without swelling. All reports of adverse events following immunization that were made to the passive surveillance system between 1994 and 2003 were included-a total of 1162 identified cases. Red, blue, purple discoloration and isolated petechiae were reported in 39, 19, 27 and 14% of these cases, respectively. Of these 1162 cases, 1105 were considered to be related to the vaccination, based on a predefined risk window with symptom onset after vaccination (48 h for discolorations and 2 weeks for petechiae). Of the 1105 cases, about 50% occurred after DTP-IPV+Hib1 vaccinations, and 30% occurred after DTP-IPV+Hib2 vaccinations. Discolored leg syndrome was frequently accompanied by fierce crying (78%). The median time interval between vaccination and the occurrence of DLS was 3.8 +/- 46.7 h, and the median duration was short (2 +/- 61.7 h). Advancing the vaccination schedule from 3 to 2 months of age caused a small increase in DLS. Discolored leg syndrome manifested mainly after the first and/or second vaccination. In addition to dose, the occurrence of DLS may be slightly age-dependent and self-limiting. The pathophysiology is unknown but may be the result of a vasomotor reaction. Future studies should elucidate the recurrence rate, identify risk factors and assess late outcomes.

The effect of age and dose number on the risk of collapse (hypotonic-hyporesponsive episode) after pertussis vaccination.

The Netherlands vaccination schedule has been advanced by 1 month. The reporting rate of collapse or hypotonic-hyporesponsive episode increased from 5.2 [95% confidence interval (CI): 4.8-5.7] to 8.5 (95% CI: 8.0-9.1) and from 1.2 (95% CI: 1.0-1.4) to 2.5 (95% CI: 2.2-2.8) per 10,000 first and second doses, respectively. At 3 months of age it fell from 5.2 to 2.5. This suggests some protection by the first dose. Different mediators in primary and secondary immune response may play a role.

Coverage of the 2011 Q fever vaccination campaign in the Netherlands, using retrospective population-based prevalence estimation of cardiovascular risk-conditions for chronic Q fever.

BACKGROUND: In 2011, a unique Q fever vaccination campaign targeted people at risk for chronic Q fever in the southeast of the Netherlands. General practitioners referred patients with defined cardiovascular risk-conditions (age >15 years). Prevalence rates of those risk-conditions were lacking, standing in the way of adequate planning and coverage estimation. We aimed to obtain prevalence rates retrospectively in order to estimate coverage of the Q fever vaccination campaign. METHODS: With broad search terms for these predefined risk-conditions, we extracted patient-records from a large longitudinal general-practice research-database in the Netherlands (IPCI-database). After validation of these records, obtained prevalence rates (stratified for age and sex) extrapolated to the Q fever high-incidence area population, gave an approximation of the size of the targeted patient-group. Coverage calculation addressed people actually screened by a pre-vaccination Q fever skin test and serology (coverage) and patients referred by their general practitioners (adjusted-coverage) in the 2011 campaign. RESULTS: Our prevalence estimate of any risk-condition was 3.1% (lower-upper limits 2.9-3.3%). For heart valve defects, aorta aneurysm/prosthesis, congenital anomalies and endocarditis, prevalence was 2.4%, 0.6%, 0.4% and 0.1%, respectively. Estimated number of eligible people in the Q fever high-incidence area was 11,724 (10,965-12,532). With 1330 people screened for vaccination, coverage of the vaccination campaign was 11%. For referred people, the adjusted coverage was 18%. Coverage was lowest among the very-old and highest for people aged 50-70 years. CONCLUSION: The estimated coverage of the vaccination campaign was limited. This should be interpreted in the light of the complexity of this target-group with much co-morbidity, and of the vaccine that required invasive pre-vaccination screening. Calculation of prevalence rates of risk-conditions based on the IPCI-database was feasible. This procedure proved an efficient tool for future use, when prevalence estimates for policy, implementation or surveillance of subgroup-vaccination or other health-care interventions are needed.

Effect of vaccinations on seizure risk and disease course in Dravet syndrome.

OBJECTIVE: To study the effect of vaccination-associated seizure onset on disease course and estimate the risk of subsequent seizures after infant pertussis combination and measles, mumps, and rubella (MMR) vaccinations in Dravet syndrome (DS). METHODS: We retrospectively analyzed data from hospital medical files, child health clinics, and the vaccination register for children with DS and pathogenic SCN1A mutations. Seizures within 24 hours after infant whole-cell, acellular, or nonpertussis combination vaccination or within 5 to 12 days after MMR vaccination were defined as "vaccination-associated." Risks of vaccination-associated seizures for the different vaccines were analyzed in univariable and in multivariable logistic regression for pertussis combination vaccines and by a self-controlled case series analysis using parental seizure registries for MMR vaccines. Disease courses of children with and without vaccination-associated seizure onset were compared. RESULTS: Children who had DS (n = 77) with and without vaccination-associated seizure onset (21% and 79%, respectively) differed in age at first seizure (median 3.7 vs 6.1 months, p < 0.001) but not in age at first nonvaccination-associated seizure, age at first report of developmental delay, or cognitive outcome. The risk of subsequent vaccination-associated seizures was significantly lower for acellular pertussis (9%; odds ratio 0.18, 95% confidence interval [CI] 0.05-0.71) and nonpertussis (8%; odds ratio 0.11, 95% CI 0.02-0.59) than whole-cell pertussis (37%; reference) vaccines. Self-controlled case series analysis showed an increased incidence rate ratio of seizures of 2.3 (95% CI 1.5-3.4) within the risk period of 5 to 12 days following MMR vaccination. CONCLUSIONS: Our results suggest that vaccination-associated earlier seizure onset does not alter disease course in DS, while the risk of subsequent vaccination-associated seizures is probably vaccine-specific.

Adverse events and association with age, sex and immunological parameters of Q fever vaccination in patients at risk for chronic Q fever in the Netherlands 2011.

BACKGROUND: Following a large Q fever outbreak in the Netherlands, patients at risk for chronic Q fever received a whole-cell Q fever vaccine. Sensitized people were excluded based on pre-vaccination screening with skin test (ST) and serology. An investigational IFN-γ-production assay was added. No previous experience existed for Q fever vaccination in this patient risk-group with predefined cardiac valvular anomalies or aortic aneurysm/prosthesis and many co-morbidities. We studied the adverse events (AE) and their association with patient characteristics and immunological parameters. METHODS: AE registration covered the week after skin test and 90 days following vaccination, with the use of diaries, interviews and spontaneous reports. Serious (S)AE were assessed immediately to ensure safety. We coded AE according to reported severity. Univariate and multivariate analysis addressed associations. RESULTS: Pre-vaccination screening led to exclusion of 182 patients with positive serology and 207 patients with positive skin test-reading. The skin test did not lead to any causally related SAE. Subsequent vaccination of 1370 patients did not reveal unexpected AE; however, 80% of vaccinees reported local AE (in 26% of these pronounced or extensive). The two causally related SAE (0.1%) both concerned a persistent subcutaneous injection site mass. AE were more frequent in women, younger patients, and those without immunosuppressive co-morbidity/medication. The occurrence of local AE after skin test was associated with pre-vaccination positive serology and high IFN-γ production. This was also true for local AE following vaccination, with a strong association with local AE after skin test as well. The proportion of vaccinees with positive serology and positive IFN-γ values 6 months after vaccination was higher in those with local AE after skin test or after vaccination (non-significant, probably due to small numbers). CONCLUSION: Q fever vaccination was safe but reactogenic in this high-risk patient-group. Rates of local AE were higher in women, younger age groups and in those with positive immunological parameters. Vaccinees with local AE after skin test or after vaccination appear to have more pronounced post-vaccination immune responses.

Etiologies for seizures around the time of vaccination.

OBJECTIVES: This study was an assessment of the incidence, course, and etiology of epilepsy with vaccination-related seizure onset in a population-based cohort of children. METHODS: The medical data of 990 children with seizures after vaccination in the first 2 years of life, reported to the National Institute for Public Health and Environment in the Netherlands in 1997 through 2006, were reviewed. Follow-up data were obtained of children who were subsequently diagnosed with epilepsy and had had seizure onset within 24 hours after administration of an inactivated vaccine or 5 to 12 days after a live attenuated vaccine. RESULTS: Follow-up was available for 23 of 26 children (median age: 10.6 years) with epilepsy onset after vaccination. Twelve children developed epileptic encephalopathy, 8 had benign epilepsy, and 3 had encephalopathy before seizure onset. Underlying causes were identified in 15 children (65%) and included SCN1A-related Dravet syndrome (formerly severe myoclonic epilepsy of infancy) or genetic epilepsy with febrile seizures plus syndrome (n = 8 and n = 1, respectively), a protocadherin 19 mutation, a 1qter microdeletion, neuronal migration disorders (n = 2), and other monogenic familial epilepsy (n = 2). CONCLUSIONS: Our results suggest that in most cases, genetic or structural defects are the underlying cause of epilepsy with onset after vaccination, including both cases with preexistent encephalopathy or benign epilepsy with good outcome. These results have significant added value in counseling of parents of children with vaccination-related first seizures, and they might help to support public faith in vaccination programs.

Implementation of a Q fever vaccination program for high-risk patients in the Netherlands.

BACKGROUND: Between 2007 and 2011 the Netherlands was faced with an unprecedented Q fever outbreak with more than 4000 people affected. Dairy goats were considered the main source of infection. In addition to taking veterinary measures, the Dutch government offered an unlicensed vaccine against the causative bacterium Coxiella burnetii to patient groups at high-risk of Q fever complications. This article describes the complexity of the vaccination program for Q fever in 2010-2011. METHODS: High-risk patients were selected and referred mainly by their general practitioner to a publicly funded centralized screening and vaccination program. In addition, cardiovascular specialists and the public were informed. Patients were screened for previous infection with C. burnetii by serology and skin-tests. Patients who tested positive were excluded from vaccination. RESULTS: Of the 2741 referred high-risk patients (1669 male, 1957 from the high-risk area), 955 were excluded because vaccination was considered unnecessary or the distance to the vaccination clinic too far. 388 (22% of those screened) were excluded because of a positive skin-test or serology. 1368 patients (77% of those screened) were vaccinated between January and June 2011. Two-thirds of the vaccinees reported an adverse event. 89 patients (6.6%) reported serious adverse events. In just one patient, with an injection site reaction, a possible causal relationship was considered. CONCLUSION: This Q fever vaccination program posed challenges to the Dutch Health Care system. Creating clarity on the roles and responsibilities of those involved precluded timely vaccination. Targeting the high-risk population through GPs was challenging but appeared to be efficient. The vaccination was considered to be safe and compliance of the screened patients was high.

Reactogenicity of infant whole cell pertussis combination vaccine compared with acellular pertussis vaccines with or without simultaneous pneumococcal vaccine in the Netherlands.

BACKGROUND: In addition to the routine enhanced passive safety surveillance of the Dutch National Vaccination Programme, RIVM (National Institute for Public Health and the Environment) started a large questionnaire study enrolling approximately 53,000 children from December 2003 until September 2007. AIM: We intended to establish accurate frequency estimates for several more severe adverse events and to compare the incidence rates of three different infant vaccines that were used consecutively. METHODS: Whole cell pertussis (wP) DTP-IPV-Hib vaccine (NVI) was replaced by acellulair pertussis (aP) in 2005, first Infanrix-IPV-Hib (GSK) followed by Pediacel (Sanofi) in 2006. Pneumococcal vaccine, Prevenar (Wyeth), was added for children born from April 2006. RESULTS: Parents returned 28,796 questionnaires (response 54%), 15,069 for whole cell pertussis and 13,727 for acellular pertussis vaccine, including 4485 with pneumococcal vaccine. The OR for reported events was 3-6 for whole cell pertussis vaccine compared with acellular vaccine. This was true for prolonged crying for 3h and more after the first dose (1.5% versus 0.4%; 95 CI 1.1-1.9 and 95% CI 0.2-0.7, respectively), and very high fever of 40.5 degrees C and over following the fourth dose (0.8% versus 0.2%; 95% CI 0.5-1.1 and 0.06-0.3, respectively), while possible febrile convulsions were diagnosed only twice after the fourth dose in the whole cell vaccine group and one after acellular pertussis vaccine. Pallor was significantly more frequent after the first dose of whole cell pertussis than after acellulair pertussis vaccination (18.3% versus 3.4%; 95% CI 17.2-19.5 and 95% CI 2.8-4.0 respectively) Collapse after the first dose was rare in both vaccine groups (5 after whole cell vaccine and 1 after acellular vaccine). The addition of conjugated pneumococcal vaccine did not result in statistically significant increased rates of adverse events in the acellular vaccine group. CONCLUSION: Whole cell pertussis vaccine showed a significantly higher reactogenicity regarding the adverse events analysed, while addition of conjugated pneumococcal vaccine administered simultaneously with acellular pertussis showed no statistically different adverse event profile.

Safety and efficacy of meningococcal c vaccination in juvenile idiopathic arthritis.

OBJECTIVE: To determine whether vaccinations aggravate the course of autoimmune diseases such as juvenile idiopathic arthritis (JIA) and whether the immune response to vaccinations may be hampered by immunosuppressive therapy for the underlying disease. METHODS: In this multicenter cohort study, 234 patients with JIA (ages 1-19 years) were vaccinated with meningococcal serogroup C (MenC) conjugate to protect against serogroup C disease (caused by Neisseria meningitidis). Patients were followed up for disease activity for 1 year, from 6 months before until 6 months after vaccination. IgG antibody titers against MenC polysaccharide and the tetanus carrier protein were determined by enzyme-linked immunosorbent assay and toxin binding inhibition assay, respectively. A serum bactericidal assay was performed to determine the function of the anti-MenC antibodies. RESULTS: No change in values for any of the 6 components of the core set criteria for juvenile arthritis disease activity was seen after MenC vaccination. Moreover, no increase in the frequency of disease relapse was detected. Mean anti-MenC IgG concentrations in JIA patients rose significantly within 6-12 weeks after vaccination. Of 157 patients tested, 153 were able to mount anti-MenC IgG serum levels >2 micro g/ml, including patients receiving highly immunosuppressive medication. The 4 patients with a lower anti-MenC antibody response displayed sufficient bactericidal activity despite receiving highly immunosuppressive medication. CONCLUSION: The MenC conjugate vaccine does not aggravate JIA disease activity or increase relapse frequency and results in adequate antibody levels, even in patients receiving highly immunosuppressive medication. Therefore, patients with JIA can be vaccinated safely and effectively with the MenC conjugate.

Performance of the Brighton collaboration case definition for hypotonic-hyporesponsive episode (HHE) on reported collapse reactions following infant vaccinations in the Netherlands.

We reviewed collapse (sudden onset of pallor, limpness and hyporesponsiveness) following the first infant (DPTP+Hib) vaccination reported to the enhanced passive surveillance system of the Netherlands in 1994-2003. All 1303 reports identified by the current RIVM (National Institute for Public Health and Environment) case definition were captured by the Brighton Collaboration (BC) case definition, with in 17 (1.3%) reports insufficient information. Over the years the proportion of the highest level of diagnostic certainty (level 1) increased due to more complete data from 70% to over 90%. We checked the BC case definition also on a sample of cases (with pallor or hyporesponsiveness) not meeting RIVM's case definition for collapse at the time. Sixty out of 200 cases were captured by BC but again rejected by RIVM. The sensitivity BC levels 2 and 3 appeared too high. We recommend a more restrict case definition by the Brighton Collaboration with certain exclusion criteria to make it more specific. Furthermore a change in the specifications for levels 2 and 3 will increase specificity and accommodate for the loss of sensitivity.

Developing a vaccination evaluation model to support evidence-based decision making on national immunization programs.

Among all public health provisions national immunization programs (NIPs) are beyond doubt one of the most effective in reducing mortality, morbidity, and costs associated with major infectious diseases. To maintain their success, NIPs have to modernize in response to many new and old demands regarding efficacy, safety, availability of new vaccines, emerging and evolving pathogens, waning immunity, altered epidemiological situations, and the public's trust in the program. In this paper we present an evaluation model in the form of a checklist that may help in collecting relevant scientific information that is necessary for evaluation and decision making when considering changes in a NIP. Such a checklist points to relevant information on the vaccine-preventable disease, the pathogen causing it, the vaccine, and the cost-effectiveness ratio of the vaccine. However, the final judgment on a potential change in the NIP cannot be based on a simple algorithm, as the relevant information reflects factors of a very different kind and magnitude, to which different value judgements may be added, and which may have certain degrees of uncertainty. Because any change in the NIP may be accompanied by more or less unforeseen changes in the vaccine's efficacy, evolutionary consequences, including the antigenic composition of the pathogen, and the vaccine's safety profile, an intensive surveillance program should accompany any NIP. Elements thereof include clinical-epidemiological surveillance, surveillance of vaccination coverage, immune surveillance, surveillance of microbial population dynamics, and surveillance of adverse events and safety issues. We emphasize that the decision to introduce a vaccine in the NIP should be taken as seriously, both scientifically and ethically, as the decision to withhold a vaccine from the NIP. In the latter case one might be responsible for vaccine-preventable disease and mortality.