HIV Prevalence in Young People
It measures progress towards reducing HIV infection.
The goal in the response to HIV is to reduce HIV infection. However, given current inability to reliably measure HIV incidence in a cross-sectional survey, proxy measures of HIV incidence are required.
HIV prevalence at any given age is the difference between the cumulative numbers of people that have become infected with HIV up to this age minus the number who have died, expressed as a percentage of the total number alive at this age. At older ages, changes in HIV prevalence are slow to reflect changes in the rate of new infections (HIV incidence) because the average duration of infection is long. Declines in HIV prevalence can reflect saturation of infection among those individuals who are most vulnerable, and rising mortality, rather than behaviour change. Increases in HIV prevalence can reflect increasing numbers of individuals receiving antiretroviral therapy, and living longer. However at younger ages, trends in HIV prevalence are a better indication of recent trends in HIV incidence and risk behaviour since young people are likely to only recently have initiated sexual or injecting drug behaviours. In addition, young people who have recently been infected with HIV are not likely to have started antiretroviral therapy. Thus, reductions in HIV incidence associated with genuine behaviour change should first become detectable in trends in HIV prevalence figures for 15–24 years olds (or even earlier in 15–19-year-olds if this age breakdown is available). Where available, parallel behavioural surveillance survey data should be used to aid interpretation of trends in HIV prevalence.
Number of antenatal clinic attendees (aged 15–24) tested whose HIV test results are positive
Number of antenatal clinic attendees (aged 15–24) tested for their HIV infection status
Numerator / Denominator
UNAIDS/WHO guidelines for HIV sentinel surveillance.
This indicator is calculated using data from pregnant women attending antenatal clinics in HIV sentinel surveillance sites in the capital city, other urban areas and rural areas.
The sentinel surveillance sites used for the calculation of this indicator should remain constant to allow for the tracking of changes over time.
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In countries where the age at which young people first have sexual intercourse is late and/or levels of contraception use are high, HIV prevalence among pregnant women of 15–24 years of age will differ from that among all women in the age group. If fertility patterns are changing this trend might be biased if women living with HIV make different fertility choices.
This indicator (using data from antenatal clinics) gives a fairly good estimate of relatively recent trends in HIV infection in locations where the epidemic is heterosexually driven. It is less reliable as an indicator of HIV-epidemic trends in locations where most infections remain temporarily confined to key populations.
To supplement data from antenatal clinics, an increasing number of countries have included HIV testing in population-based surveys. If a country has produced HIV prevalence estimates from survey data, these estimates should be included in the comments box for this indicator in order to allow for comparisons between multiple surveys. Survey-based estimates should be disaggregated by sex.
The addition of new sentinel sites will increase the samples’ representativeness and will therefore give a more robust point estimate of HIV prevalence. However, the addition of new sentinel sites reduces the comparability of values. As such it is important to use consistent sites when undertaking trend analyses.
As more children who were infected through mother to child transmission live into their reproductive years this indicator becomes less relevant. Countries should collect information on timing of infection for women with known HIV-positive sero-status to exclude these women from analyses of trends.
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