Tailoring vertical transmission programmes: model for prioritising strategies
Authors: Brodie Daniels
Journal: The Lancet Global Health (2024)

Despite the substantial reduction in vertical transmission since the peak of HIV prevalence in the early 2000s, the rapid decrease has stalled in recent years. Different factors have contributed to this slowing of progress in countries with a high HIV burden. Nearly two thirds of new infections in central and western Africa in 2022 were due to mothers not receiving antiretroviral therapy (ART) during pregnancy or breastfeeding (or both). In eastern and southern Africa, new infections were equally due to mothers not having access to ART during pregnancy or breastfeeding (or both), mothers being unable to avoid infection during pregnancy or breastfeeding (or both), and poor maternal adherence to ART.1Joint United Nations Programme on HIV/AIDSThe path that ends AIDS: UNAIDS Global AIDS update 2023. UNAIDS, Geneva2023Google Scholar It is clear that each region and country has unique challenges that must be addressed to reduce vertical transmission rates. Joshua Chevalier and colleagues developed a model assessing the cost-effectiveness and effect of multiple interventions on vertical transmission outcomes, potentially reducing the burden of deciding what interventions to add or strengthen in a vertical transmission programme.2Chevalier JM Hansen MA Coskun E et al.Cost-effectiveness of intervention combinations towards the elimination of vertical transmission of HIV in limited-resource settings: a mathematical modelling study.Lancet Glob Health. 2024; 12: e457-e466Google Scholar The model was tested using health statistics from Zambia (ie, HIV prevalence, incidence, birth rate, and breastfeeding duration), but it could easily be customised to any country wanting to assess the potential effect and cost-effectiveness of planned vertical transmission interventions. The model was used to assess nearly 200 intervention combinations, with the main outcomes being the number of infant and maternal infections averted and the cost of proposed interventions. For Zambia, the model predicted that three interventions reduced vertical transmission in a cost-effective manner (when provided to 80% of the population in need). Providing infant prophylaxis decreased infant transmission by 4·5%, maternal peer-to-peer support groups decreased vertical transmission by 35%, and three scenarios of maternal HIV retesting schedules decreased vertical transmission by just over 6%. Despite these projected gains, Chevalier and colleagues believed that these interventions, even in combination, will not decrease the Zambian vertical transmission rate to the desired target of fewer than 50 transmissions per 100 000 livebirths. However, this failure to achieve the target might not be the case if these interventions were tweaked. For example, extended infant prophylaxis (shown to be safe up to age 12 months)3Flynn PM Taha TE Cababasay M et al.Prevention of HIV-1 transmission through breastfeeding: efficacy and safety of maternal antiretroviral therapy versus infant nevirapine prophylaxis for duration of breastfeeding in HIV-1-infected women with high CD4 cell count (IMPAACT PROMISE): a randomized, open label, clinical trial.J Acquir Immune Defic Syndr. 2018; 77: 383-392Crossref PubMed Scopus (111) Google Scholar could contribute by protecting infants until maternal viral load is suppressed when mothers test HIV positive during late pregnancy (ie, the final trimester) or if they were not adherent to ART regimens. Although point-of-care viral load testing did not show potential due to the intervention cost in this model, it could be useful in specific scenarios in which mothers require additional monitoring, allowing for targeted extended infant prophylaxis. Three maternal HIV retesting scenarios were used in the model: late in antenatal care, at delivery, and 6 weeks postpartum; late in antenatal care, at delivery, or 6 weeks postpartum, and at 14 weeks postpartum; or late in antenatal care, at delivery, or 6 weeks postpartum, and at 3-monthly intervals postpartum. These scenarios could be scaled-up with maternal testing at every infant vaccine visit (6 weeks, 10 weeks, 14 weeks, 6 months, 9 months, 12 months, and 18 months). Alternatively, HIV test kits could be sent home with mothers who are counselled to self-test every month, since self-testing has been shown to be feasible and acceptable in low-income and middle-income countries.4Rivera AS Hernandez R Mag-Usara R et al.Implementation outcomes of HIV self-testing in low- and middle- income countries: a scoping review.PLoS One. 2021; 16e0250434 Crossref Scopus (16) Google Scholar Such testing could bolster maternal support groups, which showed promise in the model. These support groups could have additional value in providing breastfeeding and infant nutritional support (eg, educational support) to mothers. Although it was not included as an intervention in this model, the importance of educating women of childbearing age cannot be overlooked (whether scholarly education or continued health education). Higher educational attainment is associated with higher rates of HIV testing during antenatal care.5Allorant A Muset P Hodgins C et al.Temporal trends and determinants of HIV testing at antenatal care in sub-Saharan Africa: a pooled analysis of population-based surveys (2005–2021).J Acquir Immune Defic Syndr. 2024; 95: e97-105Crossref Scopus (1) Google Scholar Additionally, a meta-analysis showed that education level, disclosure of HIV status, having a support system, early ART initiation, and good knowledge of vertical transmission and HIV significantly increased ART adherence.6Fassinou LC Songwa Nkeunang D Delvaux T Nagot N Kirakoya-Samadoulougou F Adherence to option B + antiretroviral therapy and associated factors in pregnant and breastfeeding women in sub-Saharan Africa: a systematic review and meta-analysis.BMC Public Health. 2024; 24: 94Crossref Scopus (0) Google Scholar Chevalier and colleagues caution in their assessment that these interventions would not meet the desired vertical transmission targets in Zambia. However, the outcome of this adjusted vertical transmission programme model was not considered in an environment where additional population-level strategies were used, such as opt-out HIV testing7Creek TL Ntumy R Seipone K et al.Successful introduction of routine opt-out HIV testing in antenatal care in Botswana.J Acquir Immune Defic Syndr. 2007; 45: 102-107Crossref PubMed Scopus (140) Google Scholar and treat-all1Joint United Nations Programme on HIV/AIDSThe path that ends AIDS: UNAIDS Global AIDS update 2023. UNAIDS, Geneva2023Google Scholar strategies, which contributed to Botswana reaching the 95–95–95 target. There is also the promise of additional biomedical interventions, such as injectable long-acting antiretrovirals (for treatment and pre-exposure prophylaxis),8Meyer-Rath G Jamieson L Pillay Y What will it take for an injectable ARV to change the face of the HIV epidemic in high-prevalence countries? Considerations regarding drug costs and operations.J Int AIDS Soc. 2023; 26e26106 Google Scholar infant vaccines, and broadly neutralising antibodies.9Van de Perre P Goga A Ngandu N et al.Eliminating postnatal HIV transmission in high incidence areas: need for complementary biomedical interventions.Lancet. 2021; 397: 1316-1324Summary Full Text Full Text PDF PubMed Scopus (16) Google Scholar Although reaching these last milestones to achieve the desired targets for HIV transmission will be challenging, the outcomes will be worth the effort. This model is another tool to add to the arsenal to get each country there. I declare no competing interests. Cost-effectiveness of intervention combinations towards the elimination of vertical transmission of HIV in limited-resource settings: a mathematical modelling studyUsing the interventions modelled, it is possible to reduce vertical transmission and to cost-effectively prevent up to 1734 infant HIV infections (43% reduction) in Zambia over a period of 1 year. To optimise their effect, these interventions must be scaled with fidelity. Future work is needed to incorporate evidence on additional innovative interventions and HIV risk factors, and to apply the model to other country contexts to support targeted implementation and resource use. Full-Text PDF Open Access