Improving estimates of children living with HIV from the Spectrum AIDS Impact Model

Abstract

Objective Estimated numbers of children living with HIV determine programmatic and treatment needs. We explain the changes made to the UNAIDS estimates between 2015 and 2016 and describe the challenges around these estimates. Methods Estimates of children newly infected, living with HIV, and dying of AIDS are developed by country teams using Spectrum software. Spectrum files are available for 160 countries, which represent 98% of the global population. In 2016, the methods were updated to reflect the latest evidence on mother-to-child HIV transmission and improved assumptions on the age children initiate antiretroviral therapy. We report updated results using the 2016 model and validate these estimates against mother- to-child transmission rates and HIV prevalence from population-based surveys for the survey year. Results The revised 2016 model estimates 27% fewer children living with HIV in 2014 than the 2015 model, primarily due to changes in the probability of mother-to-child transmission among women with incident HIV during pregnancy. The revised estimates were consistent with population-based surveys of HIV transmission and HIV prevalence among children 5–9 years, but were lower than surveys among children 10–14 years. Conclusions The revised 2016 model is an improvement on previous models. Paediatric HIV models will continue to evolve as further improvements are made to the assumptions. Commodities forecasting and programme planning rely on these estimates and increasing accuracy will be critical to enable effective scale-up and optimal use of resources. Efforts are needed to improve empirical measures of HIV prevalence, incidence and mortality among children.

Living and dying to be counted: What we know about the epidemiology of the global adolescent HIV epidemic

“…Spectrum estimates are reviewed by UNAIDS for validity and consistency and are then compiled to develop regional and global estimates. Two important improvements were made to the 2016 UNAIDS estimates model specific to understanding the paediatric and adolescent HIV epidemics [21]. Based on an updated review (produced by Lynne Mofenson and commissioned by UNAIDS, and detailed in Annex 2 of reference [21]), on the probability of HIV transmission during pregnancy, delivery and breastfeeding, the number of children estimated to have become HIV infected was revised downward for current and historical years.…”

“…Two important improvements were made to the 2016 UNAIDS estimates model specific to understanding the paediatric and adolescent HIV epidemics [21]. Based on an updated review (produced by Lynne Mofenson and commissioned by UNAIDS, and detailed in Annex 2 of reference [21]), on the probability of HIV transmission during pregnancy, delivery and breastfeeding, the number of children estimated to have become HIV infected was revised downward for current and historical years. Based on multiregional analyses performed by the International Epidemiologic Database to Evaluate AIDS (IeDEA), improvements were also made to more accurately reflect at what age children initiate ART [23,24].…”

“…We interrogate global and country-specific trend differences (for the five highest adolescent HIV burden countries) between younger and older adolescents in the total number living with HIV, the number of AIDS-related deaths and the number of new infections using the 2016 UNAIDS estimates for 1990-2015. Estimates from 1990 through 2015 are used and are based on the most recent 2016 UNAIDS Spectrum model [20,21]for the current and historical years. Recent, nationally representative data from periodic population-based surveys in the 15 highest adolescent HIV burden countries are evaluated and estimates of adolescent HIV prevalence presented where available.…”

Producing HIV estimates: from global advocacy to country planning and impact measurement

“…The effects of antiretroviral prophylaxis were introduced in 2005 and new regimens have been added and were updated since then [47]. In the 2016 Spectrum/AIM module the transmission probability from mothers to their children was updated based on additional research; the most notable change was an important reduction in the transmission probability among women who seroconverted during the pregnancy [48]. …”

“…For example in 2015 UNAIDS reported there were 2.6 million children living with HIV globally. In 2016 the number was revised to 1.8 million, potentially causing confusion about whether 800,000 children living with HIV had died over the year [48]. To avoid confusion UNAIDS and partners explained the changes through multiple channels [60].…”