Incidence and Clinical Characteristics of and Risk Factors for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection Among Pregnant Individuals in the United States

Abstract

Background Data about the risk of SARS-CoV-2 infection among pregnant individuals are needed to inform infection prevention guidance and counseling for this population. Methods We prospectively followed a cohort of pregnant individuals during August 2020–March 2021 at three U.S. sites. The three primary outcomes were incidence rates of any SARS-CoV-2 infection, symptomatic infection, and asymptomatic infection, during pregnancy during periods of SARS-CoV-2 circulation. Participants self-collected weekly mid-turbinate nasal swabs for SARS-CoV-2 RT-PCR testing, completed weekly illness symptom questionnaires, and submitted additional swabs with COVID-19–like symptoms. An overall SARS-CoV-2 infection incidence rate weighted by population counts of women of reproductive age in each state was calculated. Results Among 1098 pregnant individuals followed for a mean of 10 weeks, nine percent (99/1098) had SARS-CoV-2 infections during the study. Population weighted incidence rates of SARS-CoV-2 infection were 10.0 per 1,000 (95% confidence interval [CI] 5.7–14.3) person-weeks for any infection, 5.7 per 1,000 (95% CI 1.7-9.7) for symptomatic infections, and 3.5 per 1,000 (95% CI 0-7.1) for asymptomatic infections. Among 96 participants with SARS-CoV-2 infection and symptom data, the most common symptoms were nasal congestion (72%), cough (64%), headache (59%), and change in taste or smell (54%); 28% had measured or subjective fever. The median symptom duration was 10 days (IQR6-16 days). Conclusion Pregnant individuals had a 1% risk of SARS-CoV-2 infection per week. Study findings provide information about SARS-CoV-2 infection risk during pregnancy to inform counseling for pregnant individuals about infection prevention practices, including COVID-19 vaccination.

SARS-CoV-2 incidence, transmission, and reinfection in a rural and an urban setting: results of the PHIRST-C cohort study, South Africa, 2020–21

“… 18 We found that 85·3% of infections were asymptomatic, 92·5% among individuals younger than 19 years and 76·1% among individuals aged 19 years or older, despite active symptom evaluation twice a week. Three US-based cohort studies implementing PCR testing once a week for SARS-CoV-2, irrespective of symptoms, plus additional testing with symptomatic illness, found asymptomatic fractions of 31% in a community-based household cohort including children, 35% in pregnant women, and 11% among health-care workers, 19 , 20 , 21 which are lower than the estimates in our study. The lower asymptomatic proportion in these studies could be because swabbing twice a week allows identification of transient asymptomatic illness, or because the symptomatic fraction could be truly lower in the populations included in our study.…”

SARS-CoV-2 incidence, transmission and reinfection in a rural and an urban setting: results of the PHIRST-C cohort study, South Africa, 2020-2021

“…Three US-based cohort studies implementing weekly PCR testing for SARS-CoV-2, irrespective of symptoms, found estimates of 31% asymptomatic in a community-based study including children, 35% in pregnant women and 11% among healthcare workers, lower than estimates in our study. [28][29][30] The lower symptomatic fraction in these studies could be because twice weekly-swabbing allows identification of more transient symptomatic illness or because there could be truly lower symptomatic fraction in the populations included in our study. Compared to other studies, the population included in our study was relatively young with only 9% of individuals aged ≥60 years, reflecting the general South African population.…”

Incidence of SARS-CoV-2 over four epidemic waves in a low-resource community in Rio de Janeiro, Brazil: A prospective cohort study

“…The incidence of SARS-CoV-2 in our study population during the first wave was approximately eight times higher than the incidence reported for family-based cohorts in the US. 1 , 2 Among the factors that may have contributed to the difference in incidence rates is the geographic scope of recruitment. Since the geographic areas from which families were recruited in the US were larger than that of our study, the cohorts followed in the US may have been more diverse than ours.…”

“…Evaluating rates of new infections in a cohort can provide data to inform vaccination strategies and non-pharmaceutical interventions (NPIs). As discussed below, while many studies have estimated the incidence of SARS-CoV-2 in cohorts in Europe and North America 1 , 2 , 3 , 4 relatively little is known about incident cases of SARS-CoV-2 in the Global South.…”

“… 5 , 6 A number of studies have estimated SARS-CoV-2 incidence over one particular epidemic wave. 1 , 2 , 3 , 4 However, there is no data about rates of new SARS-CoV-2 cases in low-income, high population density areas during the period of circulation of different SARS-CoV-2 lineages. Little is known about the extent to which, if any, the incidence of SARS-CoV-2 infection changes from one SARS-CoV-2 epidemic wave to another in such areas, and if so, why.…”