Viral vector vaccines and a booster can protect maternal women against the Omicron variant of COVID-19, but the mRNA vaccine with a booster dose appears to offer the best protection.
The mRNA vaccine appear to be the most effective means of preventing severe COVID-19 symptoms and complications in pregnant women, according to a recent study conducted by the Oxford Maternal and Perinatal Health Institute (OMPHI) at the University of Oxford and published in the journal Lancet.
Investigators associated Omicron infection with increased risk of maternal morbidity, severe pregnancy complications, and hospital admissions, particularly among symptomatic and unvaccinated women.
“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,” said study co-leader José Villar, MD, MPH, MSc, FRCOG, professor of Perinatal Medicine at the University of Oxford, in a press release.
Expectant mothers who were vaccinated had a very low risk of being admitted into the intensive care unit (ICU) as well, but researchers associate this very low risk with full vaccination and preferably being boosted.
The researchers conducted the INTERCOVID study to understand the impact of the COVID-19 Omicron variant on maternal and neonatal outcomes. Conducted between November 27, 2021, and June 30, 2022, across 41 hospitals worldwide, INTERCOVID 2022 studied 1545 pregnant women diagnosed with Omicron against a control group of 3073 pregnant women without an Omicron diagnosis. The investigators also evaluated vaccine efficacy.
While the key findings support full vaccination and a booster dose—which can provide 10 months of protection against severe complications from Omicron— study co-leader Aris Papageorghiou, MBChB, MRCOG, professor of Fetal Medicine at the University of Oxford, explains that many pregnant women still do not have access to full vaccination coverage.
“The large proportion of unvaccinated pregnant women worldwide are still at major risk,” Papageorghiou said in the press release.
Additionally, the data suggest that unvaccinated and severely symptomatic women are at particular risk of preeclampsia compared to participants in the control group. Generally, women who are obese or overweight and have severe symptoms are at the highest risk for maternal morbidity or severe complications.
This study, along with previous INTERCOVID studies, have led to major changes in clinical practice and public health policy recommendations for vaccination during pregnancy, explained co-leader Stephen Kennedy, MA (Oxon), MD, MRCOG, professor of reproductive medicine, University of Oxford, in the press release. Kennedy hopes the findings can prevent misinformation about vaccine safety and efficacy.
"This study provides robust evidence that vaccination against COVID Omicron variant provides protection for mothers and babies,” Jagjit Teji, MD, neonatologist and principal investigator at Lurie Children’s Hospital in Chicago, said in the press release.
Ann & Robert H. Lurie Children’s Hospital of Chicago. Vaccination provides effective protection against increased risk of pregnancy complications due to COVID-19 Omicron variant. News Release. January 18, 2023. Accessed on January 19, 2023. https://www.eurekalert.org/news-releases/977008