Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Observational Study
. 2021 Jul;8(7):e429-e439.
doi: 10.1016/S2352-3018(21)00069-2.

Age patterns of HIV incidence in eastern and southern Africa: a modelling analysis of observational population-based cohort studies

Kathryn A Risher  1 , Anne Cori  2 , Georges Reniers  3 , Milly Marston  4 , Clara Calvert  4 , Amelia Crampin  5 , Tawanda Dadirai  6 , Albert Dube  7 , Simon Gregson  8 , Kobus Herbst  9 , Tom Lutalo  10 , Louisa Moorhouse  2 , Baltazar Mtenga  11 , Dorean Nabukalu  10 , Robert Newton  12 , Alison J Price  4 , Malebogo Tlhajoane  4 , Jim Todd  4 , Keith Tomlin  4 , Mark Urassa  11 , Alain Vandormael  13 , Christophe Fraser  14 , Emma Slaymaker  4 , Jeffrey W Eaton  15 ; ALPHA Network
Affiliations
Observational Study

Age patterns of HIV incidence in eastern and southern Africa: a modelling analysis of observational population-based cohort studies

Kathryn A Risher et al. Lancet HIV. 2021 Jul.

Abstract

Background: As the HIV epidemic in sub-Saharan Africa matures, evidence about the age distribution of new HIV infections and how this distribution has changed over the epidemic is needed to guide HIV prevention. We aimed to assess trends in age-specific HIV incidence in six population-based cohort studies in eastern and southern Africa, reporting changes in mean age at infection, age distribution of new infections, and birth cohort cumulative incidence.

Methods: We used a Bayesian model to reconstruct age-specific HIV incidence from repeated observations of individuals' HIV serostatus and survival collected among population HIV cohorts in rural Malawi, South Africa, Tanzania, Uganda, and Zimbabwe, in a collaborative analysis of the ALPHA network. We modelled HIV incidence rates by age, time, and sex using smoothing splines functions. We estimated incidence trends separately by sex and study. We used estimated incidence and prevalence results for 2000-17, standardised to study population distribution, to estimate mean age at infection and proportion of new infections by age. We also estimated cumulative incidence (lifetime risk of infection) by birth cohort.

Findings: Age-specific incidence declined at all ages, although the timing and pattern of decline varied by study. The mean age at infection was higher in men (cohort mean 27·8-34·6 years) than in women (24·8-29·6 years). Between 2000 and 2017, the mean age at infection per cohort increased slightly: 0·5 to 2·8 years among men and -0·2 to 2·5 years among women. Across studies, between 38% and 63% (cohort medians) of the infections in women were among those aged 15-24 years and between 30% and 63% of infections in men were in those aged 20-29 years. Lifetime risk of HIV declined for successive birth cohorts.

Interpretation: HIV incidence declined in all age groups and shifted slightly to older ages. Disproportionate new HIV infections occur among women aged 15-24 years and men aged 20-29 years, supporting focused prevention in these groups. However, 40-60% of infections were outside these ages, emphasising the importance of providing appropriate HIV prevention to adults of all ages.

Funding: Bill & Melinda Gates Foundation.

PubMed Disclaimer

Conflict of interest statement

Declaration of interests SG, MT, ES, and JWE report grants from the Gates Foundation. SG also reports grants from the Wellcome Trust, UK Medical Research Council/Department for International Development, US National Institutes of Health, and WHO, and dividends on ordinary shares in AstraZeneca and GlaxoSmithKline, outside of the submitted work. JWE also reports grants from the UNAIDS, US NIH, and WHO, and personal fees from WHO. LM reports grants from the London School of Hygiene & Tropical Medicine. All other authors declare no competing interests.

Figures

Figure 1
Figure 1
Age-specific HIV incidence modelled estimates in six ALPHA network studies by age group (A) and by year (B) (A) Rakai does not include a line for age 45–54 years because the cohort has largely not done HIV tests in individuals older than 49 years. (B) Karonga, Manicaland, and uMkhanyakude do not include results for 2000 and 2015, 2015, and 2000, respectively, due to different start and end dates of HIV testing rounds. More details on serosurvey years are given in the appendix (p 17).
Figure 2
Figure 2
Mean age at infection in six ALPHA network studies by sex
Figure 3
Figure 3
Proportion of new HIV infections in six ALPHA network studies by age group
Figure 4
Figure 4
Narrowest age bands accounting for 25%, 50%, and 75% of new HIV infections in six ALPHA network studies
Figure 5
Figure 5
Cumulative incidence of HIV at ages 25, 35, and 50 years by birth cohort in six ALPHA network studies by sex Data are cumulative incidence of HIV at the specified ages, which were projected assuming current period age-specific incidence and assuming a continuation of the relative reduction seen in the past 5 years.
See this image and copyright information in PMC

Comment in

References

    1. UNAIDS Seizing the moment: tackling entrenched inequalities to end epidemics. 2020. https://www.unaids.org/en/resources/documents/2020/global-aids-report
    1. UNAIDS AIDSinfo: Africa–eastern and southern. 2020. https://aidsinfo.unaids.org/
    1. Reniers G, Wamukoya M, Urassa M. Data resource profile: network for analysing longitudinal population-based HIV/AIDS data on Africa (ALPHA Network) Int J Epidemiol. 2016;45:83–93. - PMC - PubMed
    1. Borgdorff MW, Kwaro D, Obor D. HIV incidence in western Kenya during scale-up of antiretroviral therapy and voluntary medical male circumcision: a population-based cohort analysis. Lancet HIV. 2018;5:e241–e249. - PubMed
    1. Gregson S, Garnett GP, Nyamukapa CA. HIV decline associated with behavior change in eastern Zimbabwe. Science. 2006;311:664–666. - PubMed

Publication types