A new investigation published in JAMA examines how COVID-19 vaccination affects maternal and perinatal outcomes among pregnant individuals infected with SARS-CoV-2, drawing on population-level data from Canada during both the Delta and Omicron waves.
Key findings
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The study analyzed 19,899 pregnant individuals with confirmed SARS-CoV-2 infection in Canada between April 2021 and December 2022.
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COVID-19 vaccination was associated with a lower risk of maternal hospitalization during both the Delta and Omicron variant periods.
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Vaccinated individuals had a substantially lower risk of critical care unit admission compared with unvaccinated individuals during both variant periods.
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Preterm birth occurred less frequently among vaccinated individuals, with reduced risk observed during the Delta and Omicron periods.
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Among the cases analyzed, 72% were vaccinated prior to COVID-19 diagnosis, with most vaccinated either before pregnancy or during pregnancy.
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After adjusting for underlying health conditions, unvaccinated pregnant individuals remained significantly more likely to be hospitalized than those vaccinated during both variant periods.
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The protective association between vaccination and reduced severe outcomes was consistent regardless of SARS-CoV-2 variant.
Study details
Of the 26,584 cases initially identified, most infections occurred among individuals aged 30 to 35 years, and 55.9% were among individuals identified as White. Overall, 72% of cases were vaccinated prior to their COVID-19 diagnosis, with most receiving vaccination before pregnancy and a smaller proportion during pregnancy. Cases spanned both major variant periods, with 6,120 during Delta and 13,799 during Omicron.
Even after adjusting for comorbid conditions, vaccination remained associated with a lower risk of hospitalization. During the Omicron period, unvaccinated individuals had an adjusted hospitalization risk more than twice that of vaccinated individuals. During Delta, the adjusted hospitalization risk among unvaccinated individuals was nearly four times higher.
Conclusion
The investigators conclude that COVID-19 vaccination before or during pregnancy is associated with a reduced risk of severe maternal disease and preterm birth among pregnant individuals who develop SARS-CoV-2 infection. The findings were consistent across variant periods, underscoring the role of vaccination in mitigating adverse outcomes during pregnancy as COVID-19 continues to circulate.
Read the original article and findings in full here.
(AI was used in part to facilitate this article.)