In a recent study published in Clinical microbiology and infectionresearchers assessed the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination on pregnant women during the Omicron wave.
During the coronavirus disease 2019 (COVID-19) pandemic, pregnant women were more likely than the general population to develop severe COVID-19. In utero mother-to-child virus transmission was found to be uncommon, and infected mothers demonstrated a strong immune response with anti-SARS-CoV-2 antibodies passed on to newborns.
Despite many studies indicating a significant maternal antibody response to SARS-CoV-2 immunization and the absence of safety concerns, vaccination rates among pregnant women remained lower than in the general population. Only a few studies have been conducted to date on the effect of the SARS-CoV-2 Omicron variant on unvaccinated and vaccinated pregnant women.
About the study
In this study, researchers compared the perinatal and maternal outcomes of SARS-CoV-2-infected women in Italy during the SARS-CoV-2 Omicron variant wave based on their vaccination protection.
The current national prospective cohort research involved pregnant women who tested COVID-19 positive within seven days of admission to an Italian maternity unit between January 1 and May 31, 2022. In addition, women reported whether they had received SARS-CoV-2 the vaccine, as well as when (before and/or at the time of pregnancy) and how many doses were received.
The primary outcome measure was SARS-CoV-2 disease severity, classified as mild, moderate, or severe. The two most severe severity categories, determined by pneumonia diagnosis, were grouped together for statistical analysis as “moderate or severe COVID-19 disease” (MSCD). Secondary outcomes included preterm birth, stillbirth, birth condition, neonatal intensive care unit (NICU) admission, and early neonatal mortality before hospital discharge.
MSCD protection was considered as an exposure variable. Women vaccinated with at least one vaccine dose at the time of pregnancy and those vaccinated with the full vaccine schedule and the first booster vaccine were protected against MSCD. On the other hand, unvaccinated women and participants who were vaccinated with either one or two vaccine doses before pregnancy and tested positive for SARS-CoV-2 at 22 or more weeks of gestation were considered unprotected. Women with incomplete vaccination information and those vaccinated with one or two doses before pregnancy and who tested positive for SARS-CoV-2 at less than 22 weeks’ gestation were considered “unknown as to protection status.”
Between January 1 and May 31, 2022, a total of 2,774 women who tested positive for SARS-CoV-2 within seven days of admission were enrolled. Protection status information was available for 2147 women, while no significant clinical or sociodemographic variations were observed between these women and the entire cohort.
According to the study definition, almost 1,069 (49.8%) individuals were protected against MSCD. Of those, 74 were vaccinated with one vaccine during pregnancy, while 596 received two, including a minimum of one dose given during pregnancy, while 327 received their first booster. In contrast, 1,078 women were considered unprotected, including 989 women who were unvaccinated and 89 who tested positive for SARS-CoV-2 at 22 or more weeks of gestation after receiving one or two doses before pregnancy. All but 26 women were immunized with the conventional vaccinations alone or in conjunction with messenger ribonucleic acid (mRNA) vaccines.
Compared to protected women, unprotected women were more likely to be younger, less educated, foreign national, and symptomatic. In addition, 96.4% were hospitalized for childbirth or obstetric reasons, while 3.6% were hospitalized for COVID-19. Eight of the latter developed severe disease, 12 developed moderate disease, and 58 developed mild disease.
MSCD disease was uncommon overall, but more prevalent among unprotected women than among protected women. Among the 41 MSCD cases, 27 of 29 unprotected women had not received any vaccine, while two were vaccinated with two doses before pregnancy. Three of the 12 protected women received the booster, while nine received two doses, the first received before and the second received during pregnancy.
Among unprotected women, seven out of eight serious cases of infection and one maternal death occurred. COVID-19 pneumonia was considered the cause of death, reported two weeks after birth. Unprotected women had a higher incidence of MSCD compared with protected women, Asian women, and those with a history of comorbidity.
Sensitivity analysis revealed that unprotected women had significantly higher MSCD risk than protected women. Furthermore, 8.7% of neonates were born preterm, predominantly late preterm, with no significant variations between unprotected and protected women, but caesarean section was reported in 34.4% and 29.3% of women, respectively. The rate of preterm birth was greater among MSCD-infected women compared with those with milder cases and those with CS. Furthermore, five out of 619 CS cases were acute/emergent due to COVID-19, and all involved MSCD-affected women.
Overall, the study results documented a low incidence of severe SARS-CoV-2 infection in pregnant women and significant effectiveness of the COVID-19 vaccine in providing protection. These statistics can serve as a basis for informing pregnant women who are unsure about the effectiveness of the vaccine and demonstrate the importance of vaccination to protect their newborns.