Reduced control of SARS-CoV-2 infection is associated with lower mucosal antibody responses in pregnant women

ImportancePregnant women are at increased risk of severe COVID-19, but the contribution of viral RNA load, the presence of infectious virus, and mucosal antibody responses remain understudied.ObjectiveTo evaluate the association of COVID-19 outcomes following confirmed infection with vaccination status, mucosal antibody responses, infectious virus recovery and viral RNA levels in pregnant compared with non-pregnant women.DesignA retrospective observational cohort study of remnant clinical specimens from SARS-CoV-2 infected patients between October 2020-May 2022.SettingFive acute care hospitals within the Johns Hopkins Health System (JHHS) in the Baltimore, MD-Washington, DC area.ParticipantsParticipants included confirmed SARS-CoV-2 infected pregnant women and matched non-pregnant women (matching criteria included age, race/ethnicity, and vaccination status).ExposureSARS-CoV-2 infection, with documentation of SARS-CoV-2 mRNA vaccination.Main Outcome(s)The primary dependent measures were clinical COVID-19 outcomes, infectious virus recovery, viral RNA levels, and mucosal anti-spike (S) IgG titers from upper respiratory tract samples. Clinical outcomes were compared using odds ratios (OR), and measures of virus and antibody were compared using either Fisher’s exact test, two-way ANOVA, or regression analyses. Results were stratified according to pregnancy, vaccination status, maternal age, trimester of pregnancy, and infecting SARS-CoV-2 variant.Results(s)A total of 452 individuals (117 pregnant and 335 non-pregnant) were included in the study, with both vaccinated and unvaccinated individuals represented. Pregnant women were at increased risk of hospitalization (OR = 4.2; CI = 2.0-8.6), ICU admittance, (OR = 4.5; CI = 1.2-14.2), and of being placed on supplemental oxygen therapy (OR = 3.1; CI =1.3-6.9). An age-associated decrease in anti-S IgG titer and corresponding increase in viral RNA levels (P< 0.001) was observed in vaccinated pregnant, but not non-pregnant, women. Individuals in their 3rdtrimester had higher anti-S IgG titers and lower viral RNA levels (P< 0.05) than those in their 1stor 2ndtrimesters. Pregnant individuals experiencing breakthrough infections due to the omicron variant had reduced anti-S IgG compared to non-pregnant women (P< 0.05).Conclusions and RelevanceIn this cohort study, vaccination status, maternal age, trimester of pregnancy, and infecting SARS-CoV-2 variant were each identified as drivers of differences in mucosal anti-S IgG responses in pregnant compared with non-pregnant women. Observed increased severity of COVID-19 and reduced mucosal antibody responses particularly among pregnant participants infected with the Omicron variant suggest that maintaining high levels of SARS-CoV-2 immunity may be important for protection of this at-risk population.Key PointsQuestionIs greater COVID-19 disease severity during pregnancy associated with either reduced mucosal antibody responses to SARS-CoV-2 or increased viral RNA levels?FindingIn a retrospective cohort of pregnant and non-pregnant women with confirmed SARS-CoV-2 infection, we observed that (1) disease severity, including ICU admission, was greater among pregnant than non-pregnant women; (2) vaccination was associated with reduced recovery of infectious virus in non-pregnant women but not in pregnant women; (3) increased nasopharyngeal viral RNA levels were associated with reduced mucosal IgG antibody responses in pregnant women; and (4) greater maternal age was associated with reduced mucosal IgG responses and increased viral RNA levels, especially among women infected with the Omicron variant.MeaningThe findings of this study provide novel evidence that, during pregnancy, lower mucosal antibody responses are associated with reduced control of SARS-CoV-2, including variants of concern, and greater disease severity, especially with increasing maternal age. Reduced mucosal antibody responses among vaccinated pregnant women highlight the need for bivalent booster doses during pregnancy.