A comparative analysis of influenza vaccination programs.
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BACKGROUND: The threat of avian influenza and the 2004-2005 influenza vaccine supply shortage in the United States have sparked a debate about optimal vaccination strategies to reduce the burden of morbidity and mortality caused by the influenza virus. METHODS AND FINDINGS: We present a comparative analysis of two classes of suggested vaccination strategies: mortality-based strategies that target high-risk populations and morbidity-based strategies that target high-prevalence populations. Applying the methods of contact network epidemiology to a model of disease transmission in a large urban population, we assume that vaccine supplies are limited and then evaluate the efficacy of these strategies across a wide range of viral transmission rates and for two different age-specific mortality distributions. We find that the optimal strategy depends critically on the viral transmission level (reproductive rate) of the virus: morbidity-based strategies outperform mortality-based strategies for moderately transmissible strains, while the reverse is true for highly transmissible strains. These results hold for a range of mortality rates reported for prior influenza epidemics and pandemics. Furthermore, we show that vaccination delays and multiple introductions of disease into the community have a more detrimental impact on morbidity-based strategies than mortality-based strategies. CONCLUSIONS: If public health officials have reasonable estimates of the viral transmission rate and the frequency of new introductions into the community prior to an outbreak, then these methods can guide the design of optimal vaccination priorities. When such information is unreliable or not available, as is often the case, this study recommends mortality-based vaccination priorities. (+info)
Free-riding, fairness and the rights of minority groups in exemption from mandatory childhood vaccination.
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The authority of government to require participation in mandatory childhood vaccination programs may not target specific groups for either participation or exemption on a discriminatory basis. This poses difficulties when allowing religious or philosophical exemptions to mandatory vaccination, because certain groups are more likely to appeal for exemption. Avoiding loss of herd immunity, then, may require either discrimination against these groups by disallowing an exemption option that is available to others, or by denying the good of an exemption option to the entire population because of the action of certain groups. To avoid this unacceptable choice, steps must be taken now to more stringently enforce exemption requirements. (+info)
The effects of socioeconomic factors on the decision to be vaccinated: the case of flu shot vaccination.
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BACKGROUND: Anti-influenza vaccination has proven cost-effective for society. In Israel, however, vaccination rates remain relatively low in comparison to other countries. OBJECTIVES: To analyze the socioeconomic and health status factors affecting the decision to be vaccinated against flu and to compare these factors to results from other countries in order to determine which segments of the adult population should be targeted for increased coverage in influenza vaccination programs. METHODS: Our source was the 1999/2000 Health Survey of the Central Bureau of Statistics for the group aged 25 and above, comprising 16,033 individuals. We used statistical methods such as the Probit regression model to estimate the effects of socioeconomic and health status variables on the decision to get a flu shot. The variables included gender, age, marital status, education, ethnic origin, religious affiliation and housing density, as well as chronic illnesses, smoking, hospitalizations, membership in health management organizations and kibbutz membership. RESULTS: Our findings indicate that being a post-1990 immigrant from the former Soviet Union, living in a densely populated house, being unmarried and smoking heavily are important factors in predicting the decision not to be vaccinated. In contrast, chronic illness, previous hospitalizations, older age, and kibbutz membership positively affected the decision to take the vaccine. CONCLUSIONS: It is necessary to identify the socioeconomic and health variables marking population sectors that are less likely to be vaccinated in order to design a suitable policy to encourage vaccination. (+info)
A 'small-world-like' model for comparing interventions aimed at preventing and controlling influenza pandemics.
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BACKGROUND: With an influenza pandemic seemingly imminent, we constructed a model simulating the spread of influenza within the community, in order to test the impact of various interventions. METHODS: The model includes an individual level, in which the risk of influenza virus infection and the dynamics of viral shedding are simulated according to age, treatment, and vaccination status; and a community level, in which meetings between individuals are simulated on randomly generated graphs. We used data on real pandemics to calibrate some parameters of the model. The reference scenario assumes no vaccination, no use of antiviral drugs, and no preexisting herd immunity. We explored the impact of interventions such as vaccination, treatment/prophylaxis with neuraminidase inhibitors, quarantine, and closure of schools or workplaces. RESULTS: In the reference scenario, 57% of realizations lead to an explosive outbreak, lasting a mean of 82 days (standard deviation (SD) 12 days) and affecting 46.8% of the population on average. Interventions aimed at reducing the number of meetings, combined with measures reducing individual transmissibility, would be partly effective: coverage of 70% of affected households, with treatment of the index patient, prophylaxis of household contacts, and confinement to home of all household members, would reduce the probability of an outbreak by 52%, and the remaining outbreaks would be limited to 17% of the population (range 0.8%-25%). Reactive vaccination of 70% of the susceptible population would significantly reduce the frequency, size, and mean duration of outbreaks, but the benefit would depend markedly on the interval between identification of the first case and the beginning of mass vaccination. The epidemic would affect 4% of the population if vaccination started immediately, 17% if there was a 14-day delay, and 36% if there was a 28-day delay. Closing schools when the number of infections in the community exceeded 50 would be very effective, limiting the size of outbreaks to 10% of the population (range 0.9%-22%). CONCLUSION: This flexible tool can help to determine the interventions most likely to contain an influenza pandemic. These results support the stockpiling of antiviral drugs and accelerated vaccine development. (+info)
Developing audit standards required for outbreaks of communicable diseases-lessons from a mumps outbreak.
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BACKGROUND: A mumps outbreak occurred in 2004-05 in England and Wales. The outbreak in the Avon area of England led to mass vaccination of 16- to 24-year-olds with the measles, mumps and rubella vaccine (MMR). The response to the outbreak was audited. Literature and web searches for audit standards were undertaken, and experts in the field were contacted. No comprehensive audit standards for outbreaks of communicable diseases were found. This article describes an approach to developing audit standards for outbreaks of communicable diseases. METHODS: Audit standards were developed based on the memorandum of understanding between the National Health Service (NHS) and Health Protection Agency. The audit was undertaken involving 25 staff. RESULTS: The audit standards developed identified many areas for improvement including training, strategic co-ordination, inter-organizational communication, consistency and timeliness of communication. Conducting the audit was problematic because there were not pre-defined audit standards. CONCLUSIONS: Audit standards should be developed, which include issues relating to the structure, process and outcome of responses to outbreaks. The development of audit standards for the management of outbreaks is crucial to evaluate outbreak control and make necessary improvements. (+info)
Neurologic adverse events associated with smallpox vaccination in the United States--response and comment on reporting of headaches as adverse events after smallpox vaccination among military and civilian personnel.
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BACKGROUND: Accurate reporting of adverse events occurring after vaccination is an important component of determining risk-benefit ratios for vaccinations. Controversy has developed over alleged underreporting of adverse events within U.S. military samples. This report examines the accuracy of adverse event rates recently published for headaches, and examines the issue of underreporting of headaches as a function of civilian or military sources and as a function of passive versus active surveillance. METHODS: A report by Sejvar et al was examined closely for accuracy with respect to the reporting of neurologic adverse events associated with smallpox vaccination in the United States. Rates for headaches were reported by several scholarly sources, in addition to Sejvar et al, permitting a comparison of reporting rates as a function of source and type of surveillance. RESULTS: Several major errors or omissions were identified in Sejvar et al. The count of civilian subjects vaccinated and the totals of both civilians and military personnel vaccinated were reported incorrectly by Sejvar et al. Counts of headaches reported in VAERS were lower (n = 95) for Sejvar et al than for Casey et al (n = 111) even though the former allegedly used 665,000 subjects while the latter used fewer than 40,000 subjects, with both using approximately the same civilian sources. Consequently, rates of nearly 20 neurologic adverse events reported by Sejvar et al were also incorrectly calculated. Underreporting of headaches after smallpox vaccination appears to increase for military samples and for passive adverse event reporting systems. CONCLUSION: Until revised or corrected, the rates of neurologic adverse events after smallpox vaccinated reported by Sejvar et al must be deemed invalid. The concept of determining overall rates of adverse events by combining small civilian samples with large military samples appears to be invalid. Reports of headaches as adverse events after smallpox vaccination appear to be have occurred much less frequently using passive surveillance systems and by members of the U.S. military compared to civilians, especially those employed in healthcare occupations. Such concerns impact risk-benefit ratios associated with vaccines and weigh against making vaccinations mandatory, without informed consent, even among military members. Because of the issues raised here, adverse event rates derived solely or primarily from U.S. Department of Defense reporting systems, especially passive surveillance systems, should not be used, given better alternatives, for making public health policy decisions. (+info)
Health benefits, risks, and cost-effectiveness of influenza vaccination of children.
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We estimated cost-effectiveness of annually vaccinating children not at high risk with inactivated influenza vaccine (IIV) to range from US $12,000 per quality-adjusted life year (QALY) saved for children ages 6-23 months to $119,000 per QALY saved for children ages 12-17 years. For children at high risk (preexisting medical conditions) ages 6-35 months, vaccination with IIV was cost saving. For children at high risk ages 3-17 years, vaccination cost $1,000-$10,000 per QALY. Among children notat high risk ages 5-17 years, live, attenuated influenza vaccine had a similar cost-effectiveness as IIV. Risk status was more important than age in determining the economic effects of annual vaccination, and vaccination was less cost-effective as the child's age increased. Thus, routine vaccination of all children is likely less cost-effective than vaccination of all children ages 6-23 months plus all other children at high risk. (+info)
An approach to prevention of infectious diseases during military deployments.
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The US military conducts missions that range from major ground combat operations to disaster and humanitarian relief efforts. A primary goal of military medical professionals is disease prevention, which can be made more difficult in the context of short preparation times and prolonged deployment duration. The military uses a 6-component approach to deployment medicine, emphasizing preparation, education, personal protective measures, vaccines, chemoprophylaxis, and surveillance in an attempt to prevent infectious diseases. Many of the components of military deployment medicine are applicable to civilian disaster relief and humanitarian missions. (+info)