Vertical transmission of HIV
When compared with values from previous years, this indicator shows the impact of providing women with antiretroviral medicines and retaining them in care to reduce vertical transmission of HIV.
Efforts have been made to increase access to interventions that can significantly reduce vertical transmission of HIV, including treatment regimens and strengthening counselling on infant feeding. The impact of interventions for preventing vertical transmission in reducing the number of children newly infected with HIV through vertical transmission needs to be assessed.
The percentage of children who are living with HIV should decrease as the coverage of interventions for preventing vertical transmission and the use of more effective regimens increase.
Estimated number of children newly infected with HIV in the previous 12 months from vertical transmission
(Although the denominator is limited to births in the past 12 months, the numerator can include children infected by HIV during the breastfeeding period and thus the birth might have occurred more than 12 months earlier. The indicator is thus actually a ratio and not a true percentage.)
Estimated number of births to women living with HIV in the previous 12 months
Ideally, this indicator would be measured through programmes identifying HIV infection in young children. However, these programmes often are not able to identify infections among children of (1) women who seroconvert while they are pregnant or breastfeeding, (2) women who do not continue in care during either antenatal or post natal services or (3) those women who never received services. Modelled estimates are used for global reporting in settings where final outcomes of vertical transmission at the population level are not available.
The probability of vertical transmission differs depending on the timing of initiating antiretroviral therapy, the antiretroviral drug regimen received and infant feeding practices. The transmission can be calculated using Spectrum. The Spectrum computer programme uses information on the following:
- The distribution of pregnant women living with HIV who are receiving antiretroviral medicines by the timing of treatment initiation (before conception, early in the pregnancy or late in the pregnancy).
- The proportion of pregnant women retained on antiretroviral medicines at the time of delivery.
- Estimated HIV incidence among pregnant women and breastfeeding women.
- The distribution of women receiving antiretroviral medicines after delivery (postpartum).
- Among women receiving antiretroviral medicines, the percentage whose infants have stopped breastfeeding by age of the child in months (from 0-35 months)
- Among women not receiving antiretroviral medicines, the percentage whose infants have stopped breastfeeding by age of the child in months (from 0-35 months)
- Among breastfeeding women receiving antiretroviral medicine, the percentage who drop out each month.
- Estimated incidence among breastfeeding women.
- Probabilities of vertical transmission of HIV based on various categories of antiretroviral medicine regimen and infant feeding practices.
- The estimated number of women living with HIV giving birth by age group.
The summary display for preventing vertical transmission in Spectrum reports the estimated national population-level transmission rate. This variable can also be calculated in Spectrum by dividing the number of children newly infected with HIV through vertical transmission by the number of women who need services for preventing vertical transmission.
Not enough information is available about other HIV transmission routes for children to include such infections in Spectrum. In addition, other modes of transmission are believed to cause a small fraction of the overall number of children acquiring HIV. The Spectrum output variable “new HIV infections for children 0–1 years” is not used because some children older than one year will acquire HIV from breastfeeding.
Global AIDS Monitoring users have the option to use their Spectrum estimate or to enter nationally representative population-level data. If Spectrum estimates are chosen, the values will be pulled directly from the software once the national file is finalized. If programme data are included, report the data based on equal birth cohorts for the numerator and denominator and not by the year of diagnosis.
This indicator is different from the United States Government MER indicator on PMTCT Final Outcome (PMTCT_FO), as the MER indicator is a cohort measure that does not capture child infections among women who seroconvert during breastfeeding or those who did not participate in (or who dropped out of) prevention of vertical transmisson programmes. The denominator is also different: the MER indicator attempts to estimate the number of women who will seroconvert during breastfeeding.
Strengths. Over time, this indicator assesses the ability of programmes to prevent vertical transmission. The modelled estimate is preferred as directly measuring this indicator is very difficult. The modelled estimate overcomes multiple challenges:
- Following up mother–child pairs is difficult, especially at the national level, because of the lag in reporting and the multiple health facility sites that mother–child pairs can visit for the wide range of services for preventing vertical transmission and child care interventions delivered over a time span.
- Children (especially those living with HIV) may die before they are tested to determine whether transmission has occurred.
- A directly measured indicator will not capture women and their children who do not attend programmes, possibly because of high levels of stigma.
- Most directly measured values will not include women who seroconvert while breastfeeding.
Weaknesses. This indicator is generated from a model that provides estimates of HIV infection among children. The estimated indicator is only as good as the assumptions and data used in the model. In countries where caesarean section is widely practised, the indicator will overestimate mother-to-child transmission. It also relies on programme data that often capture the antiretroviral medicine regimens provided rather than those consumed and could therefore underestimate vertical transmission.
This indicator does not capture efforts to reduce the risk of vertical transmission by reducing the number of reproductive-age women acquiring HIV or by reducing unintended pregnancies among women living with HIV.
In countries in which data are available, facility attendance is high and confirmatory tests are conducted systematically, efforts should be made to monitor the impact by directly assessing the percentage of children living with HIV among those born to mothers living with HIV. All countries should make efforts to monitor the HIV status and survival of children born to women living with HIV, gathered during follow-up health-care visits.
Consolidated HIV strategic information guidelines: Driving impact through programme monitoring and management. Geneva: World Health Organization, 2020 (https://www.who.int/publications/i/item/consolidated-hiv-strategic-information-guidelines).
BI.4 Final MTCT rate, 2020, WHO Consolidated HIV strategic information guidelines: driving impact through programme monitoring and management (https://www.who.int/publications/i/item/consolidated-hiv-strategic-information-guidelines).