Study reveals impact of SARS-CoV-2 infection, vaccine on pregnancy during omicron wave

Pregnant women with COVID-19, especially those with symptomatic disease and those who were not vaccinated, had worse pregnancy outcomes during the omicron wave of the pandemic, according to data published in The Lancet.

“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,” José Villar, MD, MPH, MSc, FRCOG, a professor of perinatal medicine and co-director of the Oxford Maternal and Perinatal Health Institute at the University of Oxford in England, said in a press release. “Antenatal services worldwide should strive to include vaccination against COVID-19 in the routine care of pregnant women.”

Methodology

Villar and colleagues evaluated pregnancy outcomes of deliveries at hospitals participating in the prospective, observational INTERCOVID-2022 study between Nov. 27, 2021 — the day after the omicron variant was declared a variant of concern by WHO — and June 30, 2022. The INTERCOVID-2022 study spanned 41 hospitals in 18 countries, including the United States, Nigeria, Japan, Italy and Argentina. All hospitals were also participants in the Oxford Maternal and Perinatal Health Institute network of research institutions.

The researchers identified 4,618 pregnant women delivering at a participating hospital who had a real-time polymerase chain reaction or rapid test result. With each woman with COVID-19 enrolled, two unmatched women without COVID-19 were enrolled from the same site.

Mothers and their newborns were followed through hospital discharge for adverse outcomes, which were categorized using the following indices:

• maternal morbidity and mortality index (MMMI), which included complication during pregnancy, preterm birth, infection requiring antibiotics or maternal death, ICU admission or referral to higher care;
• severe neonatal morbidity index (SNMI), which included at least one morbidity such as bronchopulmonary dysplasia, sepsis or intraventricular hemorrhage; and
• severe perinatal morbidity and mortality index (SPMMI), which included any of the SNMI morbidities, intrauterine or neonatal death or NICU stay of at least 1 week.

Findings

In total, 1,545 (33%) pregnant women had COVID-19 and 3,073 (67%) pregnant women did not have COVID-19. Among those with COVID-19, the mean gestational age at diagnosis was 33.1 weeks.

Compared with women who did not have COVID-19, those with the disease had greater risks for MMMI (RR = 1.16; 95% CI, 1.03-1.31) and SPMMI (RR = 1.21; 95% CI, 1-1.46). The risk for SNMI with vs. without COVID-19 was not significant.

Further analyses showed that COVID-19 increased the risk for maternal death, ICU admission or referral to higher care (RR = 1.5; 95% CI, 1.01-2.21).

Symptomatic disease was associated with greater risks, with the risk for MMMI being higher for women with any symptoms (RR = 1.32; 95% CI, 1.15-1.52), moderate symptoms (RR = 1.34; 95% CI, 1.12-1.61) and severe symptoms (RR = 2.51; 95% CI, 1.84-3.43) vs. women without COVID-19. Severe symptoms were also associated with higher risks for SPMMI (RR = 1.84; 95% CI, 1.02-3.34) and maternal death, ICU admission or referral to higher care (RR = 11.83; 95% CI, 6.67-20.97) vs. no disease.

Vaccination

Additionally, unvaccinated women with vs. without COVID-19 had higher risks for MMMI (RR = 1.36; 95% CI, 1.12-1.65) and maternal death, ICU admission or referral to higher care (RR = 3.33; 95% CI, 1.99-5.59).

Symptoms increased the risks for adverse events among unvaccinated women. Specifically, unvaccinated women with severe symptoms vs. no disease were more likely to experience MMMI (RR = 2.88; 95% CI, 2.02-4.12), preeclampsia, eclampsia or HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome (RR = 3.56; 95% CI, 1.03-12.33) and maternal referral to higher care, ICU admission or death (RR = 20.82; 95% CI, 10.44-41.54).

Within the cohort, 410 (9%) women were partially vaccinated, 1,598 (35%) completed a vaccine series and 878 (19%) had received a booster dose; more than half (n = 2,476; 54%) of participants had at least completed their first vaccine series.

Booster vaccination had the highest effectiveness against COVID-19 diagnosis at 30% (95% CI, 19-39). However, vaccination protected against symptomatic disease, with complete vaccination and booster vaccination at 74% (95% CI, 48-87) and 91% (95% CI, 65-98) effective against severe symptoms and maternal referral for higher care, ICU admission or death.

The findings highlight the importance of advocating for and prioritizing vaccination during pregnancy and indicate a need to include pregnant women in clinical trials in the future, Villar and colleagues wrote.

References:

• Vaccination provides effective protection against increased risk of pregnancy complications due to COVID-19 omicron variant. www.ox.ac.uk/news/2023-01-17-vaccination-provides-effective-protection-against-increased-risk-pregnancy. Published Jan. 17, 2023. Accessed Jan. 25, 2023.
• Villar J, et al. Lancet. 2023;doi:10.1016/S0140-6736(22)02467-9.