Postnatal prophylaxis and the use of presumptive HIV therapy for the prevention of vertical transmission of HIV in Canada 1997–2020

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INTRODUCTION: Presumptive HIV therapy (PHT) is recommended for post-natal HIV prophylaxis (PNP) in situations at high risk of HIV vertical transmission (VT), for both prevention of transmission and as early treatment in cases of in utero transmission. The objective of this study was to describe the risk of VT and use PHT among newborns in Canada, and specifically, factors associated with the use of PHT. METHODS: Data were analysed for all mother-infant pairs (MIPs) in the Canadian Perinatal HIV Surveillance Program (1997-2020), collected annually from 22 perinatal HIV centres in Canada. Infants were categorized as high risk (delivery viral load [dVL] ≥1000 copies/ml or maternal combined antiretroviral [cART] <4 weeks prior to delivery), moderate risk (dVL detectable and <1000 copies/ml, and maternal cART ≥4 weeks prior to delivery) and low risk (dVL undetectable and maternal cART ≥4 weeks prior to delivery). Neonatal prophylaxis and HIV transmission risk were compared between groups. RESULTS: A total of 4743 MIPs were included in the analysis. Overall, 13.3% of newborns received PHT; the most prescribed PHT regimens included combinations using zidovudine, lamivudine and nelfinavir (48.5%) or nevirapine (41.9%). While the most significant risk factor for transmission on univariate analysis was a detectable dVL ≥1000 copies/ml versus undetectable (odds ratio [OR] 27.91 [11.20-69.54]), the risk remained significantly increased at dVL between 400 and 999 copies/ml (OR 31.71 [8.31-120.98], but not at dVL between 50 and 399 copies/ml (OR 3.03 [0.72-12.81]). At dVL 50-399 copies/ml, 29.8% of infants received PHT, increasing to 46.7% at dVL 400-999 copies/ml, and 64.4% of infants at dVL≥1000 copies/ml. The overall risk of transmission was 6% in the high-risk group, 0.5% in the moderate-risk group and 0.2% in the low-risk group. CONCLUSIONS: PHT has been widely used in Canada in situations at high risk of VT, with 25% of newborns in this risk group receiving PHT as PNP. While PHT may reduce the risk of VT in high-risk situations and may be of benefit in cases of VT, these data also highlight ongoing gaps in perinatal HIV prevention in Canada.

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