Seroepidemiology of COVID-19 in pregnant women and their infants in Uganda and Malawi across multiple waves 2020-2022 (preprint)

ABSTRACT

Background: Data on SARS-CoV-2 infection in pregnancy and infancy has accumulated throughout the course of the pandemic. However, limited information is available from countries in sub-Saharan Africa (SSA). Evidence regarding asymptomatic SARS-CoV-2 infection and adverse birth outcomes are also scarce in these countries. The pregnant woman and infant COVID in Africa study (PeriCOVID Africa) is a South-South-North partnership involving hospitals and health centres in five countries Malawi, Uganda, Mozambique, The Gambia, and Kenya. The study leveraged data from three ongoing prospective cohort studies Preparing for Group B Streptococcal Vaccines (GBS PREPARE), SARS-CoV-2 infection and COVID-19 in women and their infants in Kampala and Mukono (COMAC) and Pregnancy Care Integrating Translational Science Everywhere (PRECISE). In this paper we describe the seroepidemiology of SARS-CoV-2 infection in pregnant women enrolled in sites in Uganda and Malawi, and the impact of SARS-CoV-2 infection on pregnancy and infant outcomes. Methods: The PeriCOVID study is a prospective mother-infant cohort study that recruited pregnant women at any gestation antenatally or on the day of delivery. A nasopharyngeal swab was taken from mothers at enrolment for RT-PCR confirmation of SARS-CoV-2 infection, and maternal and cord blood samples were tested for SARS-CoV-2 antibodies using Wantai and Euroimmune ELISA. The primary outcome was seroprevalence of SARS-CoV-2 antibodies in maternal blood, reported as the proportion of seropositive women by study site and wave of COVID-19 within each country. Placental transfer of antibodies was described using the geometric mean ratio (GMR). We also estimated the proportion of asymptomatic or subclinical COVID-19 infections in pregnant women using serological testing, and collected adverse pregnancy and infancy outcomes (e.g. still-birth, prematurity, maternal or infant death). Results: In total, 1379 women were enrolled, giving birth to 1387 infants. Overall, 63% of pregnant women had a SARS-CoV-2 positive serology. Over subsequent waves (delta and omicron) , in the absence of vaccination, seropositivity rose from 20% to over 80%. The placental transfer GMR was 1.7, indicating active placental transfer of anti-spike IgG. There was no association between SARS-CoV-2 antibody positivity and adverse pregnancy or infancy outcomes. Discussion: This study describes the increasing prevalence of SARS CoV-2 antibodies in pregnant woman in Uganda and Malawi across waves of SARS-CoV-2 infection. Our study adds to existing evidence that suggests under-reporting of infection if based solely on cases with clinical disease, or a positive RT-PCR for SARS-CoV-2, as most of the women in our study had asymptomatic infections and did not seek medical care. This has implications for screening in subsequent outbreaks and pandemics where protection of pregnant women and effect of infection in pregnancy on the infant are unknown.