Use of an observational cohort study to estimate the effectiveness of the New Zealand group B meningococcal vaccine in children aged under 5 years.

BACKGROUND: In July 2004 a strain-specific vaccine was introduced to combat an epidemic of group B meningococcal disease in New Zealand. We estimated the effectiveness of this vaccine in pre-school-aged children. METHODS: We conducted a cohort analysis of all children in New Zealand who were aged 6 months to <5 years at the time the vaccine became available for that age group in their area. We defined cases as children who were diagnosed with laboratory-confirmed epidemic strain meningococcal disease. We calculated person-days-at-risk using data from the National Immunization Register and population estimates from Statistics New Zealand. We estimated vaccine effectiveness as 1--relative risk. RESULTS: Compared with unvaccinated children, fully vaccinated children were five to six times less likely to contract epidemic strain meningococcal disease in the 24 months after they became eligible to receive a full vaccination series, corresponding to an estimated vaccine effectiveness of 80.0% (95% confidence interval: 52.5-91.6) for children aged 6 months to <5 years and 84.8% (95% confidence interval: 59.4-94.3) for children aged 6 months to <3 years. CONCLUSIONS: With over 3 million doses administered to individuals aged under 20 years throughout New Zealand, combined evidence from the Phase I and II clinical trials, the descriptive epidemiology of meningococcal disease, and this study provide evidence supporting the effectiveness of this vaccine in the 2 years following vaccination.

The Intensive Vaccines Monitoring Programme (IVMP): an electronic system to monitor vaccine safety in New Zealand.

New Zealand introduced a tailor-made vaccine (MeNZB) for epidemic control of Group B meningococcal disease. The Intensives Vaccine Monitoring Programme (IVMP), which prospectively collected data electronically on a cohort of children receiving vaccinations in sentinel practices across NZ, was developed as part of a national multi-faceted safety strategy. The main aim of the IVMP was to identify the presence of unexpected adverse events occurring with MeNZB vaccination. We describe the methodology and success factors plus consider the limitations encountered in this system which shows potential as a means for post-marketing vaccine and medicine surveillance in the future.

The risk of simple febrile seizures after immunisation with a new group B meningococcal vaccine, New Zealand.

As part of safety monitoring during a group B meningococcal disease vaccination campaign in New Zealand, we examined the possible excess risk of vaccine-associated simple febrile seizures (SFS). We conducted a cohort analysis using data from active hospital-based surveillance in the South Auckland area and a national immunisation register. Based on analysis of approximately 63,000 doses, we found no statistically significant increase in SFS incidence within 1, 2, 4, or 7 days after vaccination for any/all doses administered to children aged 6 months through 4 years. We concluded that the vaccine is unlikely to induce a heightened risk of SFS.

The risk of bronchiolitis hospitalisation following administration of a group B meningococcal vaccine in New Zealand.

AIM: During the Phase II clinical trials for a new group B meningococcal vaccine in New Zealand, six study participants (including five children who had been vaccinated with this vaccine) were hospitalised due to acute bronchiolitis. We examined more closely the potential association between bronchiolitis hospitalisation and this vaccine. METHODS: We used descriptive comparisons, a cohort analysis, and a matched case-control study to examine the potential association of bronchiolitis hospitalisation with the vaccine using New Zealand Health Information Service hospital discharge data and vaccination data from the National Immunisation Register. RESULTS: The distribution of hospitalised bronchiolitis cases throughout New Zealand immediately following the introduction of the vaccine was consistent with historical (pre-vaccine) patterns. Similarly, all point estimates for relative risk (cohort analysis) and odds ratio (case-control study) for assessing the potential association between bronchiolitis hospitalisation and the vaccine were less than 1.00. CONCLUSIONS: We concluded that this vaccine is not associated with an increased risk of hospitalisation for bronchiolitis.

Post-marketing safety monitoring of a new group B meningococcal vaccine in New Zealand, 2004-2006.

New Zealand introduced a new outer membrane vesicle vaccine in 2004 to combat an epidemic of group B meningococcal disease. An Independent Safety Monitoring Board oversaw intensive safety monitoring, which included hospital surveillance, health professional reporting (passive and active) and mortality monitoring. With over three million doses administered to individuals aged under 20 years, the monitoring results provide consistent evidence supporting the vaccine's safety.

Development of the Vaccine Analytic Unit's research agenda for investigating potential adverse events associated with anthrax vaccine adsorbed.

PURPOSE: In 2002, the Centers for Disease Control and Prevention established the Vaccine Analytic Unit (VAU) in collaboration with the Department of Defense (DoD). The focus of this report is to describe the process by which the VAU's anthrax vaccine safety research plan was developed following a comprehensive review of these topics. METHODS: Public health literature, surveillance data, and clinical sources were reviewed to create a list of adverse events hypothesized to be potentially related to anthrax vaccine adsorbed (AVA). From this list, a consensus process was used to select 11 important research topics. Adverse event background papers were written for each of these topics, addressing predetermined criteria. These were independently reviewed and ranked by a National Vaccine Advisory Committee (NVAC) workgroup. The adverse events included in the final priority list will be the subject of observational or other post marketing surveillance studies using the Defense Medical Surveillance System (DMSS) database. RESULTS: A review of various information sources identified over 100 potential adverse events. The review process recommended 11 topics as potentially warranting further study. The NVAC workgroup identified the following adverse event topics for study: arthritis, optic neuritis, and Stevens-Johnson syndrome/Toxic epidermal necrolysis. Two additional topics (systemic lupus erythematosus (SLE) and multiple, near-concurrent military vaccinations) were added in response to emerging public health and military concerns. CONCLUSIONS: The experience described, while specific for establishing the VAU's research agenda for the safety of the current anthrax vaccine, may be useful and adapted for research planning in other areas of public health research.

Measuring the health status gap for American Indians/Alaska Natives: getting closer to the truth.

OBJECTIVES: We compared the historical method of calculating cancer incidence rates with 2 new methods to determine which approach optimally estimates the burden of cancer among the Northwest American Indian/Alaska Native (AIAN) population. METHODS: The first method replicates the traditional way of calculating race-specific rates, and the 2 new methods use probabilistic record linkages to ascertain cancer cases. We indirectly adjusted all rates to the standard 2000 US population. RESULTS: Whereas the historical cancer incidence rates for all races are more than double those for the AIAN population, this apparent gap is considerably narrower when the all-race rates are compared with AIAN-specific rates calculated with probabilistic linkage methods. Similarly, there is no meaningful difference in incidence rates for selected site- and gender-specific cancers between the AIAN population and all races combined, and, in fact, some of these rates may be higher among the AIAN population. CONCLUSIONS: Our results suggest that the burden of cancer among the AIAN population is considerably higher than was previously understood. We recommend that a standardized approach based on probabilistic linkage methods be adopted and that adequate financial and technical support be made available for conducting routine linkage studies throughout Indian communities.

Autism and thimerosal-containing vaccines: lack of consistent evidence for an association.

BACKGROUND: In 1999, concerns were raised that vaccines containing the preservative Thimerosal might increase the risk of autism and/or other neurodevelopmental disorders. METHODS: Between the mid-1980s through the late-1990s, we compared the prevalence/incidence of autism in California, Sweden, and Denmark with average exposures to Thimerosal-containing vaccines. Graphic ecologic analyses were used to examine population-based data from the United States (national immunization coverage surveys and counts of children diagnosed with autism-like disorders seeking special education services in California); Sweden (national inpatient data on autism cases, national vaccination coverage levels, and information on use of all vaccines and vaccine-specific amounts of Thimerosal); and Denmark (national registry of inpatient/outpatient-diagnosed autism cases, national vaccination coverage levels, and information on use of all vaccines and vaccine-specific amounts of Thimerosal). RESULTS: In all three countries, the incidence and prevalence of autism-like disorders began to rise in the 1985-1989 period, and the rate of increase accelerated in the early 1990s. However, in contrast to the situation in the United States, where the average Thimerosal dose from vaccines increased throughout the 1990s, Thimerosal exposures from vaccines in both Sweden and Denmark-already low throughout the 1970s and 1980s-began to decrease in the late 1980s and were eliminated in the early 1990s. CONCLUSIONS: The body of existing data, including the ecologic data presented herein, is not consistent with the hypothesis that increased exposure to Thimerosal-containing vaccines is responsible for the apparent increase in the rates of autism in young children being observed worldwide.

Effect of racial/ethnic misclassification of American Indians and Alaskan Natives on Washington State death certificates, 1989-1997.

OBJECTIVES: This study examined effects of racial/ethnic misclassification of American Indians and Alaskan Natives on Washington State death certificates. METHODS: Probabilistic record linkage were used to match the 1989-1997 state death files to the Northwest Tribal Registry. RESULTS: We identified matches for 2819 decedents, including 414 (14.7%) who had been misclassified as non-American Indians and Alaskan Natives on the death certificates. The likelihood of being correctly classified increased 3-fold for each higher level of American Indian and Alaskan Native ancestry (odds ratio = 2.88; 95% confidence interval [CI] = 2.51, 3.30) and decreased by 6.9% per calendar year (95% CI = 2.0, 11.5). CONCLUSIONS: Systematic biases on death certificates in Washington State persist. Methods to reduce misclassification can improve data quality and enhance efforts to measure and reduce racial/ethnic health disparities.