Missed opportunities for prevention of vertical HIV transmission in Canada, 1997-2016: a surveillance study

Vertical HIV transmission has declined in Canada, but missed opportunities for prevention continue to occur. We sought to determine the adequacy, and changes over time in adequacy, of uptake of maternal and neonatal antiretroviral therapy for the prevention of vertical HIV transmission, and to determine the vertical transmission rate over time and according to adequacy of antenatal antiretroviral therapy during the combination antiretroviral therapy era in Canada. The Canadian Perinatal HIV Surveillance Program collects data annually through retrospective chart review concerning HIV-infected women and their infants. We determined receipt of adequate antiretroviral treatment (antenatal combination antiretroviral treatment for ≥ 4 wk, intrapartum intravenous zidovudine treatment and 4-6 wk of infant oral zidovudine treatment) and predictors of inadequate antenatal combination antiretroviral therapy (none or < 4 wk) in Canada in 1997-2016. We identified 3785 mother-infant pairs. Uptake of 4 weeks or more of antenatal combination antiretroviral therapy increased over time across all provinces/territories and regardless of maternal race/ethnicity or risk category ( < 0.001). During 2011-2016, 92 women (6.5%) received no or less than 4 weeks of antenatal combination antiretroviral therapy, 146 women (10.7%) received no intrapartum zidovudine treatment, and 43 infants (3.1%) received less than 4 weeks of zidovudine treatment. In multivariate analysis restricted to 2011-2016, higher uptake of adequate antenatal combination antiretroviral therapy was seen among black women than among Indigenous (odds ratio [OR] 2.99, 95% confidence interval [CI] 1.23-7.26) or white (OR 1.87, 95% CI 0.99-1.27) women and in British Columbia/Yukon Territory than in Alberta (OR 3.31, 95% CI 1.06-10.32), Ontario (OR 3.16, 95% CI 1.08-9.26) or Quebec (OR 3.44, 95% CI 1.09-10.84). Among the 14 vertical HIV transmission events during 2011-2016 (vertical transmission rate 1.0%), maternal HIV infection was diagnosed before the onset of labour in 5 cases, and only 2 women received adequate antenatal combination antiretroviral therapy. Efforts to improve timely access to care, HIV screening and treatment for all women, combined with enhanced resources targeting populations at increased risk for HIV infection, will be needed if vertical HIV transmission is to be eliminated in Canada.