title: 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.
authors.affiliation: The Kirby Institute,UNSW Australia,Sydney,NSW,Australia.
authors.forename: D G
authors.identifier: 0000-0002-2893-0969
authors.initials: DG
authors.lastname: Regan
authors.affiliation: The School of Public Health and Community Medicine,UNSW Australia,Sydney,NSW,Australia.
authors.forename: J G
authors.initials: JG
authors.lastname: Wood
authors.affiliation: École Nationale Supérieure de Techniques Avanceés,Palaiseau Cedex,France.
authors.forename: C
authors.initials: C
authors.lastname: Benevent
authors.affiliation: The Kirby Institute,UNSW Australia,Sydney,NSW,Australia.
authors.forename: H
authors.initials: H
authors.lastname: Ali
authors.affiliation: The Kirby Institute,UNSW Australia,Sydney,NSW,Australia.
authors.forename: L Watchirs
authors.initials: LW
authors.lastname: Smith
authors.affiliation: South Eastern Area Laboratory Services,Prince of Wales Hospital,Sydney,NSW,Australia.
authors.forename: P W
authors.initials: PW
authors.lastname: Robertson
authors.affiliation: The School of Public Health and Community Medicine,UNSW Australia,Sydney,NSW,Australia.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ferson
authors.affiliation: Central Clinical School,Monash University,Melbourne,VIC,Australia.
authors.forename: C K
authors.initials: CK
authors.lastname: Fairley
authors.affiliation: The Kirby Institute,UNSW Australia,Sydney,NSW,Australia.
authors.forename: B
authors.initials: B
authors.lastname: Donovan
authors.affiliation: The Kirby Institute,UNSW Australia,Sydney,NSW,Australia.
authors.forename: M G
authors.initials: MG
authors.lastname: Law
mesh_terms: D000293:Adolescent; D000328:Adult; D050936:Basic Reproduction Number; D004196:Disease Outbreaks; D006506:Hepatitis A / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology; D022362:Hepatitis A Vaccines / Q000008:administration & dosage*; D017957:Hepatitis A Virus, Human / Q000276:immunology*; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009517:New South Wales / Q000453:epidemiology; D014611:Vaccination; D055815:Young Adult
chemical_list: D022362:Hepatitis A Vaccines
keywords: Immunity threshold; men who have sex with men; reproduction number; transmission