Chlamydia vaccine willingness among young adults in Australia

Sexually transmitted infections (STIs) are among the most frequently reported diseases to Australia's National Notifiable Diseases Surveillance System, with chlamydia being notably prevalent among individuals aged 15-29 years. The study aims to assess the acceptability of chlamydia vaccine and the factors influencing it by investigating the awareness, knowledge and sexual behaviours of sexually active young adults in Australia.

In August 2024, an online survey was administered to sexually active young Australians aged 18-29 years using Life in Australia, a probability-based panel of the Social Research Centre, and the i-Link non-probability panel. Data from both samples were statistically blended and weighted to represent this population. A total of 1002 surveys were completed and included in the analysis.

Despite high awareness of STIs (93.3 %), particularly regarding chlamydia (88.4 %), there were misconceptions about transmission. Overall, 46.1 % had undergone STI testing, and 27.9 % considered themselves at-risk. Among those tested, chlamydia (14.7 %) was the most frequently reported infection. Human immunodeficiency virus was the greatest concern among those perceiving themselves at risk (43.0 %), followed by genital herpes (15.8 %). Notably, 84.1 % expressed willingness to receive a multi-STI vaccine, and 79.7 % were willing to take a chlamydia-only vaccine. Odds of willingness to get vaccinated were higher for 18-24-year-olds compared with 25-29-year-olds (adjusted odds ratio [aOR] = 2.5; 95 % confidence interval [CI]: 1.4, 4.2) and higher for those who had been vaccinated against human papillomavirus (aOR = 2.9; 95 % CI: 1.7, 5.0). Prevention of new infections and reduction in transmission were the main reasons for vaccination interest.

Young Australians were highly aware of STIs but demonstrated specific knowledge gaps. Despite moderate testing rates, the relatively low risk perception suggests the need for better public health communication and knowledge-raising campaigns. A strong willingness to get vaccinated against multiple STIs, particularly chlamydia, indicates potential for future vaccine development and research.