Microbiome & Microbiology Review

By Bhavana KunkalikarJan 25 2023Reviewed by Danielle Ellis, B.Sc.

In a recent study published in the Clinical Microbiology and Infection, researchers assessed the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination on pregnant women during the Omicron wave.

Background

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 viral transmission was shown 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 substantial maternal antibody response to SARS-CoV-2 immunization and the absence of safety issues, the vaccination rate among pregnant women remained lower than that of the general population. Only a few studies have been undertaken to date on the impact of the SARS-CoV-2 Omicron variant on unvaccinated and vaccinated pregnant women.

About the study

In the present 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 hospitalization in any Italian maternity unit between January 1 and May 31 2022. In addition, women reported whether they had received the SARS-CoV-2 vaccine, as well as the 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 comprised preterm birth, stillbirth, delivery mode, admission to the neonatal intensive care unit (NICU), and early neonatal mortality before hospital release.

MSCD protection was taken into account as an exposure variable. Women vaccinated with a minimum of 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 prior to pregnancy and tested positive for SARS-CoV-2 at 22 or more gestational weeks were deemed unprotected. Women with incomplete vaccination information and those who were vaccinated with one or two doses prior to pregnancy and who tested positive for SARS-CoV-2 at less than 22 gestational weeks were deemed “unknown in terms of protective status.”

Results

Immunology eBook

Compilation of the top interviews, articles, and news in the last year.

Download a free copy

Between January 1 and May 31, 2022, a total of 2,774 women who tested positive for SARS-CoV-2 within seven days of hospitalization were enrolled. Information was available about the protection status of 2147 women, while no significant clinical or socio-demographic variations were noted between these women and the entire cohort.

According to the study’s definition, almost 1,069 (49.8%) individuals were protected against MSCD. Of them, 74 were vaccinated with one vaccine during pregnancy, while 596 received two, including a minimum of one dose administered during pregnancy, while 327 received their first booster. In contrast, 1,078 women were deemed 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 except 26 women were immunized with the conventional vaccinations alone or in conjunction with messenger ribonucleic acid (mRNA) vaccines.

Compared to protected women, unprotected women displayed a higher likelihood of being younger, less educated, of foreign nationality, and symptomatic. Also, 96.4% were hospitalized for childbirth or obstetrical causes, whereas 3.6% were hospitalized due to COVID-19. Eight of the latter acquired severe disease, 12 developed a moderate disease, and 58 developed a mild disease.

MSCD illness 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 prior to pregnancy. Three of the 12 protected women received the booster, while nine received two doses, among which the first was received before and the second was received during pregnancy.

Among unprotected women, seven out of eight severe infection cases and one maternal fatality occurred. COVID-19 pneumonia was deemed the cause of death, reported two weeks after delivery. Unprotected women had a greater incidence of MSCD compared to protected women, Asian women, and those with a history of comorbidities.

Sensitivity analysis revealed that unprotected women had considerably higher MSCD risk than protected women. Furthermore, 8.7% of newborns were born preterm, predominantly late preterm, with no significant variations between unprotected and protected women, but C-section was reported in 34.4% and 29.3% of women, respectively. The rate of preterm birth was greater among MSCD-infected women compared to those with milder cases and those with CS. Also, out of 619 CS cases, five were urgent/emergent due to COVID-19, and all involved MSCD-affected women.

Conclusion

Overall, the study findings documented a low prevalence of severe SARS-CoV-2 infection in pregnant women and considerable efficacy of the COVID-19 vaccine in providing protection. These statistics can serve as the foundation for informing pregnant women uncertain about the vaccine’s efficacy and demonstrating the importance of vaccination in protecting their newborns.