COVID-19 Vaccine, Boosters Especially Important for Pregnant Women

Oxford, UK—Expectant mothers who contracted COVID-19’s omicron variant had increased risks of maternal morbidity, severe pregnancy complications, and hospital admission, especially among symptomatic and unvaccinated women, according to a new study.

The report from INTERCOVID-2022, a large, prospective, observational study involving 41 hospitals across 18 countries noted that the risk of preeclampsia was increased among women with severe symptoms. At highest risk for maternal morbidity and severe complications were obese/overweight women with severe symptoms, according to the article in Lancet.

On the other hand, University of Oxford–led researchers pointed out that vaccinated women were well protected against severe COVID-19 symptoms and complications and had a very low risk of admission to an ICU. “Prevention of severe COVID-19 symptoms and complications requires women to be completely vaccinated, preferably with a booster dose as well,” the researchers emphasized.

The background information in the article stated that in 2021, an increased risk associated with COVID-19 in pregnancy was demonstrated, adding, “Since then, the SARS-CoV-2 virus has undergone genetic mutations. We aimed to examine the effects on maternal and perinatal outcomes of COVID-19 during pregnancy, and evaluate vaccine effectiveness, when omicron (B.1.1.529) was the variant of concern.”

For INTERCOVID-2022, women with real-time polymerase chain reaction or rapid test, laboratory-confirmed COVID-19 in pregnancy were compared with two unmatched women without a COVID-19 diagnosis who were recruited concomitantly and consecutively in pregnancy or at delivery. The study team followed mother and neonate dyads until hospital discharge. The primary outcomes were defined as maternal morbidity and mortality index (MMMI), severe neonatal morbidity index (SNMI), and severe perinatal morbidity and mortality index (SPMMI).

The 4,618 pregnant women who participated were enrolled from November 27, 2021 (the day after the World Health Organization declared omicron a variant of concern), to June 30, 2022. In the cohort, 33% of women had a COVID-19 diagnosis (median gestation 36.7 weeks; interquartile range, 29.0-38.9) and 67% women with similar demographic characteristics, did not have a COVID-19 diagnosis.

“Overall, women with a diagnosis had an increased risk for MMMI (relative risk [RR] 1.16; 95% CI, 1.03-1.31) and SPMMI (RR 1.21; 95% CI, 1.00-1.46),” the authors wrote. “Women with a diagnosis, compared with those without a diagnosis, also had increased risks of SNMI (RR 1.23; 95% CI, 0.88-1.71), although the lower bounds of the 95% CI crossed unity. Unvaccinated women with a COVID-19 diagnosis had a greater risk of MMMI (RR 1.36; 95% CI, 1.12-1.65). Severe COVID-19 symptoms in the total sample increased the risk of severe maternal complications (RR 2.51; 95% CI, 1.84-3.43), perinatal complications (RR 1.84; 95% CI, 1.02-3.34), and referral, intensive care unit (ICU) admission, or death (RR 11.83; 95% CI, 6.67-20.97).”

The authors added that severe COVID-19 symptoms in unvaccinated women increased the risk of MMMI (RR 2.88; 95% CI, 2.02-4.12) and referral, ICU admission, or death (RR 20.82; 95% CI, 10.44-41.54). In the study group, 63% of the total participants had at least one single dose of any vaccine, and 54% had either complete or booster doses.

The study team calculated vaccine effectiveness (all vaccines combined) for preventing severe complications of COVID-19 for all women with a complete regimen at 48% (95% CI, 22-65) and 76% (95% CI, 47-89) after a booster dose. For women with a COVID-19 diagnosis, vaccine effectiveness of all vaccines combined for women with a complete regimen was 74% (95% CI, 48-87) and 91% (95% CI, 65-98) after a booster dose.

“COVID-19 in pregnancy, during the first 6 months of omicron as the variant of concern, was associated with increased risk of severe maternal morbidity and mortality, especially among symptomatic and unvaccinated women,” the authors concluded. “Women with complete or boosted vaccine doses had reduced risk for severe symptoms, complications, and death. Vaccination coverage among pregnant women remains a priority.”

Severe COVID-19 symptoms in the total sample increased the risk of severe maternal complications (RR 2.51; 95% CI, 1.84-3.43), perinatal complications (RR 1.84; 95% CI, 1.02-3.34), and referral, ICU admission, or death (RR 11.83; 95% CI, 6.67-20.97]). Severe COVID-19 symptoms in unvaccinated women increased the risk of MMMI (RR 2.88; 95% CI, 2.02-4.12) and referral, ICU admission, or death (RR 20.82; 95% CI, 10.44-41.54). In total, 2,886 (63%) of 4,618 participants had at least one single dose of any vaccine, and 2,476 (54%) of the 4,618 participants had either complete or booster doses. Vaccine effectiveness (all vaccines combined) for severe complications of COVID-19 for all women with a complete regimen was 48% (95% CI, 22-65) and 76% (95% CI, 47-89) after a booster dose. For women with a COVID-19 diagnosis, vaccine effectiveness of all vaccines combined for women with a complete regimen was 74% (95% CI, 48-87) and 91% (95% CI, 65-98) after a booster dose.

“COVID-19 in pregnancy, during the first 6 months of omicron as the variant of concern, was associated with increased risk of severe maternal morbidity and mortality, especially among symptomatic and unvaccinated women,” the study concluded. “Women with complete or boosted vaccine doses had reduced risk for severe symptoms, complications, and death. Vaccination coverage among pregnant women remains a priority.”

José Villar, professor of perinatal medicine at the University of Oxford, who co-led INTERCOVID 2022, advised, “We have provided robust, evidence-based information on the increased risk of the COVID-19 omicron variant during pregnancy for severe maternal complications among symptomatic and unvaccinated women. Of concern is that severe symptoms of the disease occurred in 4% to 7% of unvaccinated women diagnosed with the COVID-19 omicron variant during pregnancy. The study clearly indicates the need for a complete vaccination course during pregnancy, preferably with a booster, to provide protection for at least 10 months after the last dose. Antenatal services worldwide should strive to include vaccination against COVID-19 in the routine care of pregnant women.”

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