Drivers, barriers, and implications of mpox vaccine uptake in Australia among gay, bisexual, and other men who have sex with men: results from a prospective observational mixed-methods study (2022-2024)

Abstract

Background: Unlike other high-income countries that experienced mpox outbreaks in 2022, Australia had low case numbers before a significant resurgence in 2024, with 99 % of cases occurring in males. Vaccine coverage among gay, bisexual, and other men who have sex with men (GBMSM) was estimated at 50 %. We identified drivers and barriers to vaccine uptake and discuss implications for mpox control in Australia.

Methods: The TraX study, established in 2022, was a mixed-method prospective observational study of GBMSM and their sexual partners tracking mpox vaccine uptake through weekly surveys. Two multivariable logistic regression models identified predictors of receiving one and two doses. We analyzed qualitative responses from unvaccinated participants using the Framework Method.

Results: A total of 3596 participants were recruited through a waitlist, vaccine hubs, and community networks. In 2024, 1224 responded and were included in this analysis. Among community-recruited participants, 82.8 % had received at least one dose, associated with living in areas where ≥5 % of residents were gay men, living with HIV, recent sexually transmitted infections (STIs), greater COVID-19 vaccine history, non-relationship sex, group sex, international travel, and mpox concern. Among all participants, 83.7 % had completed the second dose, associated with older age and non-relationship sex. In qualitative analysis of 57 unvaccinated participants, most cited low perceived risk based on geography or sexual behavior. Reported barriers included difficulty accessing services, limited vaccine knowledge, and concerns about side effects.

Conclusions: This study found high uptake of the first mpox vaccine dose and a high rate of second dose completion. Most participants made decisions aligned with public health guidance, though some underestimated their risk. With low vaccine coverage and natural immunity, Australia's 2024 mpox outbreak likely reflected insufficient population-level protection. Australia likely entered 2024 with little infection induced immunity because few cases had occurred in 2022-2023, and with incomplete vaccine coverage among people at ongoing risk. Our findings point to practical steps to prevent future outbreaks by increasing vaccination rates, including addressing side-effect concerns, streamlining vaccination, and improving awareness of personal risk factors.

Keywords: Gay, bisexual, and other men who have sex with men (GBMSM); Mpox (formerly monkeypox); Mpox resurgence; Vaccine barriers; Vaccine drivers; Vaccine uptake.