{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T11:44:58Z","timestamp":1791373498822,"version":"4.3.1"},"reference-count":39,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T00:00:00Z","timestamp":1758672000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Reprod. Health"],"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>Vocational high school students in China exhibit higher rates of sexual activity than their academic counterparts; however, existing studies predominantly focus on college populations, leaving a critical gap in longitudinal data tracking the evolution of sexual knowledge and behavioural patterns among vocational students. This study aimed to evaluate changes over time in sexual safety knowledge, STIs\/HIV and reproductive health-related sexual behaviours among boys who have had sex in Chinese vocational high schools.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In 2015 and 2021, an anonymous survey was conducted separately using the same questionnaire and survey method among students in Years 1\u20132 of the same vocational high school in a district of Zhejiang Province. The results of the two surveys were compared using univariate analyses, and multivariate analyses.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>In 2015 and 2021, 180 and 90 male students, respectively, had ever had sex, representing rates of 17.44% (180\/1,032) and 8.49%(90\/1,060). The results of the multivariate analysis showed that, in 2021, those who knew that sexual contact was the main mode of HIV transmission(OR\u2009=\u200914.14, 95% CI: 7.16\u201327.92), knew that contracting an STI increased the likelihood of HIV infection (OR\u2009=\u20097.83, 95% CI: 4.30\u201314.29), and knew that condom use could reduce both STIs(OR\u2009=\u200933.51, 95% CI: 15.08\u201374.49) and HIV infection(OR\u2009=\u200916.77, 95% CI: 8.58\u201332.76) were significantly more prevalent than in 2015. Furthermore, students who had received sex and STI\/HIV prevention education and rated it as \"good\" (OR\u2009=\u20095.62, 95% CI: 2.72\u201311.64), who believed they could confidently refuse sex without a condom(OR\u2009=\u20091.95, 95% CI: 1.14\u20133.32), and who reported consistent condom use(OR\u2009=\u20092.27, 95% CI: 1.21\u20134.25) were also more prevalent in 2021. Use of contraception methods such as condoms(OR\u2009=\u20092.76, 95% CI: 1.50\u20135.09), the pill(OR\u2009=\u20092.42, 95% CI: 1.35\u20134.35), extracorporeal ejaculation (OR\u2009=\u20091.77, 95% CI:1.02\u20133.09), and the safe period(OR\u2009=\u20092.22, 95% CI: 1.22\u20134.04) also increased significantly. However, the proportion of students who had their first sexual relationship with a non-regular partner decreased(OR\u2009=\u20090.47, 95% CI: 0.24\u20130.93).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>The participants' knowledge of safe sex and sexual behaviour improveed between the two surveys. However, these positive changes have not had a significant enough impact to prevent STIs\/HIV transmission and reduce pregnancy. Further efforts are needed to ensure that these changes lead to effective STIs\/HIV prevention and reduction among students.<\/jats:p><\/jats:sec>","DOI":"10.3389\/frph.2025.1653622","type":"journal-article","created":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T05:41:05Z","timestamp":1758692465000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Changes in knowledge of safe sex and sexual behaviour among male vocational high school students in Zhejiang Province, China: a 6-year cross-sectional comparison 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