Abstract
Objective
SARS‐CoV‐2 infection in pregnancy is associated with increased risk of adverse maternal and perinatal outcomes including preterm birth, pre‐eclampsia, stillbirth, admission to intensive care unit and death. Vaccines are highly effective in preventing severe COVID‐19, however there are limited data on COVID‐19 vaccines in pregnancy. This study aimed to investigate the reactogenicity and immunogenicity of the COVID‐19 vaccine in pregnant women when given using the UK's extended 12‐week interval schedule.
Methods
This was a cohort study of pregnant women receiving COVID‐19 vaccination between January and September 2021. The primary outcome was immunogenicity and reactogenicity after COVID‐19 vaccination in pregnant women. Pregnant women were recruited by phone, email and text. They were vaccinated according to vaccine availability at their local vaccination hub and blood samples were taken at specific time points after each vaccine for nucleoprotein (N) and spike protein (S) antibodies. The comparator group comprised non‐pregnant female healthcare workers in the same age‐group who were vaccinated as part of the national immunization programme in a contemporaneous longitudinal cohort study. Association of variables with antibody levels was assessed using linear regression analysis after log‐transforming antibody levels. Reactogenicity assessment in pregnant women was undertaken using an online questionnaire. The comparator group comprised non‐pregnant women aged 18‐49 years who had received two vaccine doses in primary care. The association of pregnancy status with reactogenicity was assessed using logistic regression analysis.
Results
Overall 67 pregnant women including 66 who had received an mRNA vaccine and 50 non‐pregnant women were included in the immunogenicity study. Most pregnant women (61.2%) received the vaccine in the third trimester, while 3.0% received it in their first and 35.8% in the second trimesters. SARS‐CoV‐2 S‐antibody GMCs after mRNA vaccination were not significantly different at 2‐6 weeks after the first dose but were significantly lower at 2‐6 weeks after the second dose of vaccine in infection‐naïve pregnant compared to non‐pregnant women. In pregnant women, prior infection was associated with higher antibody levels compared to infection‐naïve women at 2‐6 weeks after both vaccine doses.
The reactogenicity analysis included 108 pregnant women and 116 non‐pregnant women. After the first dose, tiredness and chills were reported less commonly in pregnant women when compared to non‐pregnant women (P=0.043 and P=0.029, respectively). After the second dose feeling generally unwell was reported less commonly (P=0.046) in pregnant women when compared to non‐pregnant women.
Conclusions
Using an extended 12‐week interval between vaccine doses, antibody responses after 2 doses of mRNA vaccine were found to be lower in pregnant women than in non‐pregnant women. However, Antibody responses to mRNA vaccination were lower in pregnant women when compared to non‐pregnant women. High antibody responses were achieved after one dose in previously infected women, regardless of pregnancy status. Pregnant women had fewer adverse effects after both the first and the second dose of the vaccine. These findings should now be addressed in larger controlled studies.
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