Background An estimated 2·1 million individuals are newly infected with HIV every year. Cross-sectional and
longitudinal studies have reported confl icting evidence for the association between education and HIV risk, and no
randomised trial has identifi ed a causal eff ect for education on HIV incidence. We aimed to use a policy reform in
secondary schooling in Botswana to identify the causal eff ect of length of schooling on new HIV infection.
Methods Data for HIV biomarkers and demographics were obtained from the nationally representative household
2004 and 2008 Botswana AIDS Impact Surveys (N=7018). In 1996, Botswana reformed the grade structure of
secondary school, expanding access to grade ten and increasing educational attainment for aff ected cohorts. Using
exposure to the policy reform as an instrumental variable, we used two-stage least squares to estimate the causal eff ect
of years of schooling on the cumulative probability that an individual contracted HIV up to their age at the time of the
survey. We also assessed the cost-eff ectiveness of secondary schooling as an HIV prevention intervention in
comparison to other established interventions.
Findings Each additional year of secondary schooling caused by the policy change led to an absolute reduction in the
cumulative risk of HIV infection of 8·1 percentage points (p=0·008), relative to a baseline prevalence of 25·5% in the
pre-reform 1980 birth cohort. Eff ects were particularly large in women (11·6 percentage points, p=0·046). Results
were robust to a wide array of sensitivity analyses. Secondary school was cost eff ective as an HIV prevention
intervention by standard metrics (cost per HIV infection averted was US$27 753).
Interpretation Additional years of secondary schooling had a large protective eff ect against HIV risk in Botswana,
particularly for women. Increasing progression through secondary school could be a cost-eff ective HIV prevention
measure in HIV-endemic settings, in addition to yielding other societal benefi ts.
Funding Takemi Program in International Health at the Harvard T.H.Chan School of Public Health, Belgian American
Educational Foundation, Fernand Lazard Foundation, Boston University, National Institutes of Health
