Abstract Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine ...performance under ‘real world’ conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential.
Abstract The case-control methodology is frequently used to evaluate vaccine effectiveness post-licensure. The results of such studies provide important insight into the level of protection afforded ...by vaccines in a ‘real world’ context, and are commonly used to guide vaccine policy decisions. However, the potential for bias and confounding are important limitations to this method, and the results of a poorly conducted or incorrectly interpreted case-control study can mislead policies. In 2012, a group of experts met to review recent experience with case-control studies evaluating vaccine effectiveness; we summarize the recommendations of that group regarding best practices for data collection, analysis, and presentation of the results of case-control vaccine effectiveness studies. Vaccination status is the primary exposure of interest, but can be challenging to assess accurately and with minimal bias. Investigators should understand factors associated with vaccination as well as the availability of documented vaccination status in the study context; case-control studies may not be a valid method for evaluating vaccine effectiveness in settings where many children lack a documented immunization history. To avoid bias, it is essential to use the same methods and effort gathering vaccination data from cases and controls. Variables that may confound the association between illness and vaccination are also important to capture as completely as possible, and where relevant, adjust for in the analysis according to the analytic plan. In presenting results from case-control vaccine effectiveness studies, investigators should describe enrollment among eligible cases and controls as well as the proportion with no documented vaccine history. Emphasis should be placed on confidence intervals, rather than point estimates, of vaccine effectiveness. Case-control studies are a useful approach for evaluating vaccine effectiveness; however careful attention must be paid to the collection, analysis and presentation of the data in order to best inform evidence-based vaccine policies.
To determine pneumococcal polysaccharide vaccine efficacy in selected populations at risk for serious pneumococcal infection for whom vaccination is currently recommended and to assess duration of ...protection after vaccination.
Vaccine efficacy was estimated using indirect cohort analysis to compare the proportion of pneumococcal infections caused by serotypes included in the vaccines of vaccinated and unvaccinated persons who were identified during 14 years of national surveillance.
Hospital laboratories in the United States that submitted pneumococcal isolates to the Centers for Disease Control and Prevention between May 1978 and April 1992.
A total of 2837 persons older than 5 years who had pneumococcus isolated from blood or cerebrospinal fluid.
Overall efficacy for preventing infection caused by serotypes included in the vaccine was 57% (95% confidence interval CI, 45% to 66%). Efficacy among persons with diabetes mellitus was 84% (95% CI, 50% to 95%); with coronary vascular disease, 73% (95% CI, 23% to 90%); with congestive heart failure, 69% (95% CI, 17% to 88%); with chronic pulmonary diseases, 65% (95% CI, 26% to 83%); and with anatomic asplenia, 77% (95% CI, 14% to 95%). Efficacy was not documented for patients with alcoholism or cirrhosis, sickle cell disease, chronic renal failure, lymphoma, leukemia, or multiple myeloma, although sample sizes were small for these groups. Efficacy for immunocompetent persons older than 65 years was 75% (95% CI, 57% to 85%). Efficacy did not decline with increasing interval after vaccination: 5 to 8 years after vaccination it was 71% (95% CI, 24% to 89%), and 9 years or more after vaccination it was 80% (95% CI, 16% to 95%).
Intensified efforts to improve pneumococcal vaccine coverage among certain populations for whom vaccination is currently recommended is indicated, but universal revaccination is not warranted at this time.
Two hundred twenty-one Gambian children vaccinated previously with one, two, or three doses of a meningococcal conjugate vaccine or two doses of polysaccharide vaccine before the age of 6 months were ...revaccinated at the age of 18-24 months with either meningococcal polysaccharide, conjugate, or inactivated polio vaccines. Children who had previously received one, two, or three doses of conjugate vaccine had significantly (P < .001) higher anti-group C meningococcal antibody levels following revaccination than did children vaccinated with a polysaccharide vaccine for the first time. Children vaccinated previously with two doses of polysaccharide vaccine had a lower group C antibody response than did control children. Group A antibody responses following revaccination of children who had previously received polysaccharide or conjugate vaccine were not significantly higher than those in control children. Thus, immunologic memory was probably induced by the group C but not by the group A component of the conjugate vaccine.
Effective Haemophilus influenzae type b (Hib) conjugate vaccines were first licensed for use in US children at least 18 months old in December 1987 and for infants at least 2 months old in October ...1990. We evaluated trends in Hib disease associated with licensure of Hib conjugate vaccines.
Data from two sources, an intensive laboratory-based active surveillance system and the National Bacterial Meningitis Reporting System (NBMRS), were used separately to evaluate disease incidence. Data from vaccine manufacturers on Hib vaccine doses distributed in the United States were compared with trends in Hib disease incidence.
The age-specific incidence of Hib disease among children less than 5 years old decreased by 71% from 37 per 100,000 persons in 1989 to 11 per 100,000 persons in 1991 (active surveillance data). Haemophilus influenzae meningitis incidence decreased by 82% between 1985 and 1991 (NBMRS data). Increases in doses of Hib vaccine distributed in the United States coincided with steep declines in Hib disease. Both surveillance systems showed decreased rates of Hib disease in infants less than 1 year old before vaccine was licensed for use in this age group. Haemophilus influenzae type b disease incidence in persons at least 12 years old and pneumococcal meningitis incidence in children less than 5 years old did not change substantially during the same period; therefore, decreased Hib disease in children less than 5 years old is not likely to be explained solely by changes in surveillance sensitivity or decreases in bacterial disease due to changes in medical practice.
Our data suggest that conjugate vaccines have already had a marked impact on the incidence of Hib disease in the United States, preventing an estimated 10,000 to 16,000 cases of Hib disease in 1991. The decline of disease in infants less than 1 year old before licensure for this age group warrants further investigation.
Listeriosis Gellin, B.G; Broome, C.V
JAMA : the journal of the American Medical Association,
03/1989, Letnik:
261, Številka:
9
Journal Article
Recenzirano
This article reviews the history, microbiology, ecology, pathogenesis, epidemiology, and clinical spectrum of human illnesses caused by L monocytogenes and highlights areas in which further research ...efforts are particularly important
The current epidemic of violence in America threatens not only our physical health but also the integrity of basic social institutions such as the family, the communities in which we live, and our ...health care system. Public health brings a new vision of how Americans can work together to prevent violence. This new vision places emphasis on preventing violence before it occurs, making science integral to identifying effective policies and programs, and integrating the efforts of diverse scientific disciplines, organizations, and communities. A sustained effort at all levels of society will be required to successfully address this complex and deeply rooted problem.
In Los Angeles County, California, 142 cases of human listeriosis were reported from January 1 through August 15, 1985. Ninety-three cases (65.5 percent) occurred in pregnant women or their ...offspring, and 49 (34.5 percent) in nonpregnant adults. There were 48 deaths: 20 fetuses, 10 neonates, and 18 nonpregnant adults. Of the nonpregnant adults, 98 percent (48 of 49) had a known predisposing condition. Eighty-seven percent (81 of 93) of the maternal/neonatal cases were Hispanic. Of the Listeria monocytogenes isolates available for study, 82 percent (86 of 105) were serotype 4b, of which 63 of 86 (73 percent) were the same phage type. A case-control study implicated Mexican-style soft cheese (odds ratio, 5.5; 95 percent confidence interval, 1.2 to 24.8) as the vehicle of infection; a second case-control study showed an association with one brand (Brand A) of Mexican-style soft cheese (odds ratio, 8.5; 95 percent confidence interval, 2.4 to 26.2). Laboratory study confirmed the presence of L. monocytogenes serogroup 4b of the epidemic phage type in Brand A Mexican-style cheese. In mid-June, all Brand A cheese was recalled and the factory was closed. An investigation of the cheese plant suggested that the cheese was commonly contaminated with unpasteurized milk. We conclude that the epidemic of listeriosis was caused by ingestion of Brand A cheese contaminated by one phage type of L. monocytogenes serotype 4b.
Between June 30th and August 30th, 1983, 49 patients in Massachusetts acquired listeriosis. Seven cases occurred in fetuses or infants and 42 in immunosuppressed adults; 14 patients (29 per cent) ...died. Of 40 Listeria monocytogenes isolates available for testing, 32 were serotype 4b. Two case-control studies, one matching for neighborhood of residence and the other for underlying disease, revealed that the illness was strongly associated with drinking a specific brand of pasteurized whole or 2 per cent milk (odds ratio = 9, P less than 0.01 for the neighborhood-matched study; odds ratio = 11.5, P less than 0.001 for the illness-matched study). The association with milk was further substantiated by four additional analyses that suggested the presence of a dose-response effect, demonstrated a protective effect of skim milk, associated cases with the same product in an independent study in another state, and linked a specific phage type with the disease associated with milk. The milk associated with disease came from a group of farms on which listeriosis in dairy cows was known to have occurred at the time of the outbreak. Multiple serotypes of L. monocytogenes were isolated from raw milk obtained from these farms after the outbreak. At the plant where the milk was processed, inspections revealed no evidence of improper pasteurization. These results support the hypothesis that human listeriosis can be a foodborne disease and raise questions about the ability of pasteurization to eradicate a large inoculum of L. monocytogenes from contaminated raw milk.
More than two decades have passed since the development of the first successful polysaccharide vaccines for the prevention of group A and C meningococcal disease. Since then additional polysaccharide ...vaccines have been developed for serogroups Y and W135. These vaccines are poorly immunogenic in infants and small children and have a limited duration of protection in children. Substantial progress in the field of immunology has enhanced our ability to make polysaccharide antigens immunogenic in infants. Because disease caused by Neisseria meningitidis continues to cause substantial morbidity and mortality, particularly in the developing countries of the African meningitis belt, it is important that these advances be applied to the production of new effective meningococcal vaccines that could be incorporated into routine infant immunization programs. Although individual host risk factors such as complement component deficiencies have been described, risk factors for epidemic disease remain poorly understood. This review will focus on the epidemiology and prevention of meningococcal disease with an emphasis on the epidemiology of meningococcal disease in Africa and the progress in vaccine development in recent years.
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