6.1 HIV prevalence among population aged 15-24 years

Modified on 2012/10/01 14:30 by MDG Wiki Handbook — Categorized as: Uncategorized



Goal 6. Combat HIV/AIDS, malaria and other diseases
Target 6.A. Have halted by 2015 and begun to reverse the spread of HIV/AIDS


The prevalence of Human Immunodeficiency Virus (HIV) among the population 15–24 years of age is the number of individuals aged 15–24 living with HIV expressed as a percentage of the total population aged 15-24.

Human Immunodeficiency Virus (HIV) is a virus that weakens the immune system, ultimately leading to Acquired Immuno Deficiency Syndrome (AIDS). HIV destroys the body’s ability to fight off infection and disease, which can ultimately lead to death. Without treatment, median survival from the time of infection is about 10.5 years for males and 11.5 years for females. Access to treatment is uneven, and no vaccine is currently available.

Method of computation
This indicator is calculated by dividing the number of cases of HIV among the population aged 15–24 years by the total population aged 15–24 and multiplying by 100.


HIV and AIDS are major public health problems in many countries. Indicators for monitoring the HIV epidemic and the impact of interventions are crucial. Since about 40 per cent of all new HIV cases are among people 15 to 24 years old, this indicator is especially important. Moreover, changes in HIV prevalence reflect changes in the rate of new infections (HIV incidence). Trends in HIV prevalence for young age groups are considered to better reflect a country’s overall trend in HIV incidence and risk behaviour.


For generalized epidemics, antenatal clinic attendees and population based surveys are the primary sources of data. In concentrated and low level epidemics (where HIV prevalence in pregnant women is below 1 per cent), surveillance should focus on populations with high risk behaviours such as injecting drug users, men who have sex with men and sex workers.

Inclusion of HIV testing is being increasingly adopted by countries in household surveys like the Demographic and Health Surveys (DHS) and AIDS Indicator Surveys (AIS).


This indicator should be disaggregated by sex, location (urban/rural, major regions/provinces), and socio-economic characteristics such as education level and wealth quintile when possible.


HIV prevalence among young people aged 15–24 years is a better proxy for monitoring overall HIV incidence than prevalence among people aged 15–49 years. Trends in HIV prevalence for older age groups are slow to reflect changes in HIV incidence because of the long average duration of HIV infection. However, comparable data for younger age groups are still limited, even as countries are increasingly collecting better data on young people, mainly by capturing data on young pregnant women attending antenatal clinics. In the meantime, HIV prevalence among 15–49 year olds is frequently used to measure HIV prevalence trends.

An important limitation of this indicator is that trends in HIV prevalence do not necessarily reflect the impacts of interventions to reduce HIV. Declines in HIV prevalence may be the result of infection saturation among the most vulnerable individuals and/or rising mortality rates rather than changes in behaviour. The use of parallel behavioural surveillance survey data is recommended to help interpret HIV prevalence trends.


Women are more likely to acquire HIV from men during sexual intercourse than vice versa. In addition to this physiological disadvantage, the unequal social status of women throughout the world places them at a higher risk of contracting HIV. Women are at a disadvantage when it comes to accessing information about HIV prevention, the ability to negotiate safe sexual encounters and access to treatment for HIV/AIDS once infected. As a result of these inequities and epidemic dynamics, the proportion of women among people living with HIV/AIDS has been rising in many regions. In sub-Saharan Africa, women and girls are affected disproportionately by HIV; they account for approximately 60 per cent of estimated HIV infections.


Data for global and regional monitoring are produced by the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS). MDG Indicator 6.1 “HIV prevalence among population aged 15-24 years” was chosen as a proxy indicator for incidence rate when the indicators for the Millennium Declaration were developed. However, data for the younger population are limited, while estimated incidence rates among people 15-49 years are now available for a larger number of countries.

Incidence is the best measure of ongoing spread of HIV in a country, while prevalence among the population aged 15-49 years can be seen as an indicator of the overall burden of HIV/AIDS in a country. However, it is important to remember that changes overtime are difficult to follow using prevalence among population 15-49 years, and will be even more difficult as coverage of antiretroviral treatment becomes wider. A stable prevalence in the population aged 15-49 is a positive trend in the short perspective; people living with HIV are not dying as they used to do.

The UNAIDS Epidemiology team collaborates with national counterparts to generate national HIV estimates for women and men. Different approaches are used for generalized epidemics (where adult HIV prevalence exceeds 1 per cent and transmission is mostly heterosexual), and low-level or concentrated epidemics (where HIV is below 1 per cent and is concentrated in groups with behaviours that expose them to a high risk of HIV infection).

For countries with generalized epidemics, surveillance data from HIV-tested blood samples of pregnant women attending antenatal clinics and HIV prevalence results from population-based surveys are entered into the UNAIDS/WHO Estimation and Projection Package software, which generates a curve that estimates the evolution of adult HIV prevalence rates over time. This adult prevalence curve, along with national population estimates obtained from the United Nations Population Division, antiretroviral therapy (ART) coverage in adults, pregnant women and children, and various epidemiological assumptions (fertility rates, male/female population ratios, survival time after HIV infection, HIV sex and age distribution) are entered into the software, which estimates numbers of adults and children infected, new infections, deaths, orphans and treatment needs.

For countries with low-level or concentrated epidemics, surveillance data are gathered for populations at high risk (such as sex workers, men who have sex with men and injecting drug users). Estimates are made of the sizes of those populations, and of the sizes of populations that are at lower but significant risk (such as the partners of sex workers and their clients, partners of injecting drug users, etc.). That information is then processed as described above.

Country estimates are collected and reviewed based on new findings at the country level, as well as previous data trends. Country data are validated by country representatives for accuracy. Regional workshops are conducted every 2 years to produce draft estimates of HIV prevalence. These are finalized through correspondence with the country. No adjustments are made for international comparability since the data are already comparable because of standardized methodologies. There is no treatment of missing values. When the information needed to calculate the indicator is not available, the indicator is not estimated.

Improved methods, enhanced data and new estimation tools are enabling a better understanding of the degrees of uncertainty that surround HIV and AIDS estimates. This is part of an ongoing process of improving estimates and developing appropriate ranges—all of which are vital for effective HIV/AIDS planning and programming at national and regional levels.

Data quality and ranges of uncertainty surrounding data estimates vary from country to country. Ranges of uncertainty define the boundaries within which actual HIV prevalence lies. The following three factors determine the extent of the ranges around HIV estimates for adults:
  1. The HIV prevalence level. Ranges tend to be relatively smaller when HIV prevalence is higher. For example, in one country with a 15 per cent prevalence the bounds of the number of adults living with HIV is + or – 9 per cent around a best estimate of 1 million people. By contrast, in one country with a 0.8 per cent prevalence, the range is + or – 51 per cent around a best estimate of 14,000 people.

  2. The quality of the data. Countries with better quality data have smaller ranges than countries with poorer quality data. The ranges for Asia and the Pacific are comparatively broad—which reflects the fact that HIV surveillance of key populations (such as injecting drug users, sex workers and men who have sex with men) is relatively poor in most countries in that region, hence resulting in more uncertainty. In general, the ranges for sub-Saharan Africa are narrower, because of recent improvements in the collection and interpretation of HIV data in that region (including the availability of national survey data for most countries).

  3. The type of epidemic (generalized or low-level/concentrated). Ranges tend to be wider in countries with low-level or concentrated epidemics than in countries with generalized epidemics because in low-level or concentrated epidemics, both the numbers of people in the groups at higher risk of HIV infection and HIV prevalence rates need to be estimated.

Assumptions, methodologies and data used to produce the estimates are gradually changing as a result of ongoing enhancement of the knowledge of the epidemic; hence comparisons of recent estimates with those published in previous years may yield misleading conclusions.

There is a lag between the reference year and the actual production of data. Regional estimates are published in December and country estimates the following July in the Global Report.




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