PrEP offers little extra benefit to successful and safe conception for couple with an HIV negative woman and HIV positive man if he is receiving ART, they limit unprotected sex to ovulation, and STIs are treated -- according to modelling data presented at IAS 2013.
The model also suggests that younger age of the negative woman reduces the risk of transmission by decreasing the number of unprotected sex acts required for her to conceive.
Researchers from Los Angeles developed the model to estimate the annual probability of a woman remaining HIV negative, conceiving via unprotected sex with an HIV positive man and delivering a child according to various clinical scenarios. Raphael Landovitz showed data from the model in an oral presentation.
The aim of the study was to evaluate the additive benefit of PrEP for successful conception, without HIV transmission in this setting and explore the relative benefits of ART and PrEP, alone and in combination. It also evaluated the impact of maternal age on annual successful conception and non-transmission of HIV.
The primary outcome is an HIV negative woman remaining negative and successfully conceiving and developing a child.
Inputs included: transmissibility, the man receiving ART, the woman receiving PrEP, number of sex acts, female fertility by age and assuming STIs are treated. The sampling method and ranges for each parameter were chosen based a review of the relevant literature including data from HPTN-052 and Partners PrEP.
The model simulated two scenarios:
- Optimal -- unprotected sex limited to ovulation (0 to 12 acts per month -- sampled about 3)
- Suboptimal -- unprotected sex acts not limited to ovulation (0 to 60 acts per month -- sampled about 15).
In both scenarios this revealed that the HIV positive man being on ART has the greatest influence on HIV transmission.
With an optimal scenario the annual probability of a woman remaining HIV negative and delivering a child was: 27.6% with no ART or PrEP; 29.5% with PrEP; 30.6% with ART and 30.7% with treatment and PrEP. All pairwise comparisons were highly significant (p<0.0001) except for ART vs ART and PrEP, which was non-significant.
A suboptimal scenario gave these annual probabilities: 17.0% with no ART or PrEP; 24.1% with PrEP; 29.3% with ART and 30.3% with treatment and PrEP. In this scenario, all pairwise comparisons were also highly significant.
Comparing results from each annual probability calculation in optimal and suboptimal scenarios was highly significant for all comparisons.
In the optimal scenario, age is the most important factor for an HIV negative woman delivering a child. In the suboptimal scenario, for women <40 years, ART is the next most important factor.
Dr Landovit summarised, based the inputs to this model, PrEP provides little added benefit if all the following are true: the HIV positive man is receiving ART; unprotected sex is limited to the period of ovulation and STIs are diagnosed and treated in both partners.
He noted that in the optimised scenario, there is little absolute difference between all four strategies, but in the suboptimal scenario, ART for the HIV positive man drives the differences between strategies. The model also highlights that younger maternal age is associated with the desired outcome.
He stressed that all model results are limited by inputs, and are no substitute for clinical decision-making on an individual basis. But the data are reassuring that people can achieve the desired results without adding PrEP if they are able to optimise the other modifiable risk factors and they have access to ART.
The model was developed by clinicians as a tool to help couples understand the risks of HIV transmission during conception, and to allow couples and health workers to better understand the role of maternal and the benefit of PrEP for conception.
The benefits of pre-exposure prophylaxis as an adjunctive method of HIV-1 prevention during attempted conception between HIV-1-uninfected women and HIV-1-infected male partners: a modelling approach. 7th IAS Conference on HIV Pathogenesis Treatment and Prevention, 30 June - 3 July 2013, Kuala Lumpur, Malaysia. Oral Abstract TUAC0104.
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