Trends in Severe Acute Respiratory Syndrome Coronavirus 2 ( SARS‐CoV ‐2) infection and vaccine antibody prevalence in a multi‐ethnic inner‐city antenatal population: A cross‐sectional surveillance study

Abstract Objective To determine severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) seroprevalence in pregnancy in an inner‐city setting and assess associations with demographic factors and vaccination timing. Design Repeated cross‐sectional surveillance study. Setting London maternity centre. Sample A total of 906 pregnant women attending nuchal scans, July 2020–January 2022. Methods Blood samples were tested for IgG antibodies against SARS‐CoV‐2 nucleocapsid (N) and spike (S) proteins. Self‐reported vaccination status and coronavirus disease 2019 (COVID‐19) infection were recorded. Multivariable regression models determined demographic factors associated with seroprevalence and antibody titres. Main outcome measures Immunoglobulin G N‐ and S‐protein antibody titres. Results Of the 960 women, 196 (20.4%) were SARS‐CoV‐2 seropositive from previous infection. Of these, 70 (35.7%) self‐reported previous infection. Among unvaccinated women, women of black ethnic backgrounds were most likely to be SARS‐CoV‐2 seropositive (versus white adjusted risk ratio [aRR] 1.88, 95% CI 1.35–2.61, p < 0.001). Women from black and mixed ethnic backgrounds were least likely to have a history of vaccination with seropositivity to S‐protein (versus white aRR 0.58, 95% CI 0.40–0.84, p = 0.004; aRR 0.56, 95% CI 0.34–0.92, p = 0.021, respectively). Double vaccinated, previously infected women had higher IgG S‐protein antibody titres than unvaccinated, previously infected women (mean difference 4.76 fold‐change, 95% CI 2.65–6.86, p < 0.001). Vaccination timing before versus during pregnancy did not affect IgG S‐antibody titres (mean difference −0.28 fold‐change, 95% CI −2.61 to 2.04, p = 0.785). Conclusions This cross‐sectional study demonstrates high rates of asymptomatic SARS‐CoV‐2 infection with women of black ethnic backgrounds having higher infection risk and lower vaccine uptake. SARS‐CoV‐2 antibody titres were highest among double‐vaccinated, infected women. This article includes Author Insights, a video abstract available at: https://emckclac‐my.sharepoint.com/:v:/g/personal/k1888594_kcl_ac_uk/ESBeVJ8VdMtMtDOaAflgfLIBoKJ6i7g8v‐OkeQEc8cyTnA?e=v3fXo8 .