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Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

ABSTRACT: Several outbreaks of hepatitis A in men who have sex with men (MSM) were reported in the 1980s and 1990s in Australia and other countries. An effective hepatitis A virus (HAV) vaccine has been available in Australia since 1994 and is recommended for high-risk groups including MSM. No outbreaks of hepatitis A in Australian MSM have been reported since 1996. In this study, we aimed to estimate HAV transmissibility in MSM populations in order to inform targets for vaccine coverage in such populations. We used mathematical models of HAV transmission in a MSM population to estimate the basic reproduction number (R 0) and the probability of an HAV epidemic occurring as a function of the immune proportion. We estimated a plausible range for R 0 of 1·71-3·67 for HAV in MSM and that sustained epidemics cannot occur once the proportion immune to HAV is greater than ~70%. To our knowledge this is the first estimate of R 0 and the critical population immunity threshold for HAV transmission in MSM. As HAV is no longer endemic in Australia or in most other developed countries, vaccination is the only means of maintaining population immunity >70%. Our findings provide impetus to promote HAV vaccination in high-risk groups such as MSM.

SUBMITTER: Regan DG

PROVIDER: S-EPMC9150569 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

Regan D G DG Wood J G JG Benevent C C Ali H H Smith L Watchirs LW Robertson P W PW Ferson M J MJ Fairley C K CK Donovan B B Law M G MG

Epidemiology and infection 20151113 7

Several outbreaks of hepatitis A in men who have sex with men (MSM) were reported in the 1980s and 1990s in Australia and other countries. An effective hepatitis A virus (HAV) vaccine has been available in Australia since 1994 and is recommended for high-risk groups including MSM. No outbreaks of hepatitis A in Australian MSM have been reported since 1996. In this study, we aimed to estimate HAV transmissibility in MSM populations in order to inform targets for vaccine coverage in such populatio ...[more]

PMID: 26566273

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Project description:BackgroundTo combat the hesitancy towards implementing a hepatitis A universal mass vaccination (UMV) strategy and to provide healthcare authorities with a comprehensive analysis of the potential outcomes and benefits of the implementation of such a vaccination program, we projected HAV seroprevalence and incidence rates in the total population of the Russian Federation and estimated the pediatric vaccination threshold required to achieve an incidence level of less than 1 case per 100,000 using a new mathematical model.MethodsA dynamic age-structured SEIRV (susceptible-exposed-infectious-recovered-vaccinated) compartmental model was developed and calibrated using demographic, seroprevalence, vaccination, and epidemiological data from different regions of the Russian Federation. This model was used to project various epidemiological measures.ResultsThe projected national average age at the midpoint of population immunity increases from 40 years old in 2020 to 50 years old in 2036 and is shifted even further to the age of 70 years in some regions of the country. An increase of varying magnitude in the incidence of symptomatic HAV infections is predicted for all study regions and for the Russian Federation as a whole between 2028 and 2032, if the HAV vaccination coverage level remains at the level of 2022. The national average vaccination coverage level required to achieve a symptomatic HAV incidence rate below 1 case per 100,000 by 2032 was calculated to be 69.8% if children aged 1-6 years are vaccinated following the implementation of a UMV program or 34.8% if immunization is expanded to children aged 1-17 years.ConclusionThe developed model provides insights into a further decline of herd immunity to HAV against the background of ongoing viral transmission. The current favorable situation regarding hepatitis A morbidity is projected to be replaced by an increase in incidence rates if vaccination coverage remains at the current levels. The obtained results support the introduction of a hepatitis A UMV strategy in the Russian Federation.

Project description:INTRODUCTION:HIV testing is an essential prerequisite for accessing treatment with antiretroviral therapy or prevention using pre-exposure prophylaxis. Internet distribution of HIV self-tests is a novel approach, and data on the programmatic cost of this approach are limited. We analyse the costs and cost-effectiveness of a self-testing programme. METHODS:Men who have sex with men (MSM) reporting unknown or negative HIV status were enrolled from March to August 2015 into a 12-month trial of HIV self-testing in the United States. Participants were randomly assigned either to the self-testing arm or the control arm. All participants received information on HIV testing services and locations in their community. Self-testing participants received up to four self-tests each quarter, which they could use themselves or distribute to their social network associates. Quarterly follow-up surveys collected testing outcomes, including number of tests used and new HIV diagnoses. Using trial expenditure data, we estimated the cost of implementing a self-testing programme. Primary outcomes of this analysis included total programme implementation costs, cost per self-test completed, cost per person tested, cost per new HIV diagnosis among those self-tested and cost per quality adjusted life year (QALY) saved. RESULTS:A total of 2665 men were assigned either to the self-testing arm (n = 1325) or the control arm (n = 1340). HIV testing was reported by 971 self-testing participants who completed a total of 5368 tests. In the control arm, 619 participants completed 1463 HIV tests. The self-testing participants additionally distributed 2864 self-tests to 2152 social network associates. Testing during the trial identified 59 participants and social network associates with newly diagnosed HIV infection in the self-testing arm; 11 control participants were newly diagnosed with HIV. The implementation cost of the HIV self-testing programme was $449,510. The cost per self-test completed, cost per person tested at least once, and incremental cost per new HIV diagnosis was $61, $145 and $9365 respectively. We estimated that self-testing programme potentially averted 3.34 transmissions, saved 14.86 QALYs and nearly $1.6 million lifetime HIV treatment costs. CONCLUSIONS:The HIV self-testing programme identified persons with newly diagnosed HIV infection at low cost, and the programme is cost saving.

Dataset Information

Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

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Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

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