Estimating the annual number of hepatitis C virus infections through vertical transmission at country, regional, and global levels: a data synthesis study

Background:
The hepatitis C virus (HCV) burden among women of childbearing age remains high globally. Recent studies have estimated that 7-12% of children born to women with HCV infection will acquire HCV, although 66% of children will then clear their HCV infection by 5 years of age. At country, regional, and global levels, we estimated the annual number of vertically transmitted HCV infections and how many cases remain at 5 years of age.

Methods:
We produced estimates of vertical HCV transmission by combining data from several sources, including data on the number of women, age-specific fertility rates, mortality rates among children aged 0-5 years, and HIV prevalence among women aged 15-49 from the United Nations (UN), modelled data on HCV prevalence among women aged 15-49 years, review data on HCV/HIV coinfection prevalences, and recent estimates of vertical HCV transmission and subsequent clearance. The annual number of births with HCV was estimated by multiplying the number of women with HCV in 5-year age bands by the age band-specific birth rates, separately by HIV status, and multiplying by the HIV status-specific HCV vertical transmission probabilities. The number of births with HCV was multiplied by the probability of spontaneous clearance of HCV by 5 years of age, accounting for mortality. All estimates were sampled 1000 times from their uncertainty/confidence intervals to produce 95% uncertainty intervals (95%UI).

Results:
The estimated annual global number of new HCV infections occurring through vertical transmission is 73862 (95%CrI: 69808-78279). Southern Asia (21245 [18095-24847]), Western Africa (16482 [14873-18283]), and Eastern Africa (8182 [7479-9085]) were the regions with the most infections. Pakistan (16350 [13324-19844]) and Nigeria (8483 [6944-10184]) accounted for 34% of new infections. We estimated that 23120 (20596-25813) of these children would be alive and still have HCV when aged 5 years.

Discussion:
Targeted screening policies that test and treat pregnant women with HCV could prevent substantial numbers of new HCV infections, however, data on the safety of HCV treatments in pregnant women are required.