Maternal Outcomes After Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection in Vaccinated Compared With Unvaccinated Pregnant Patients : Obstetrics & Gynecology

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Contents: Research Letter

Maternal Outcomes After Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection in Vaccinated Compared With Unvaccinated Pregnant Patients

Morgan, John A. MD; Biggio, Joseph R. Jr MD, MS; Martin, Jane K. MD; Mussarat, Naiha MD; Chawla, Harsheen K. BSc; Puri, Priya BSc; Williams, Frank B. MD

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doi: 10.1097/AOG.0000000000004621
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In Brief


In early July 2021, the Centers for Disease Control and Prevention reported that the Delta (B.1.617.2) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became the dominant strain in parts of the United States, leading to a fourth surge in cases.1 Areas with low vaccination acceptance experienced high community-infection rates, thus contributing to an increase in SARS-CoV-2 infections in fully vaccinated individuals (breakthrough infection).1,2

Recent data from the Centers for Disease Control and Prevention suggest that two-dose mRNA vaccine effectiveness against SARS-CoV-2 infection is decreasing in the context of the Delta variant surge; however, the vaccine remains protective against severe sequela of SARS-CoV-2 infection.3–5 Pregnancy is an independent risk factor for severe coronavirus disease 2019 (COVID-19); however, it is currently unknown whether pregnant patients with breakthrough infection remain at high risk for severe disease.6 The primary objective of this study is to evaluate the incidence of severe or critical COVID-19 in vaccinated compared with unvaccinated pregnant patients in the context of Delta variant predominance.


This is a retrospective cohort study of all active pregnancies in the Ochsner Health System between June 15, 2021, and August 20, 2021. This study was approved by the Ochsner Clinic Foundation Institutional Review Board on August 8, 2021. Patients were compared according to vaccination status. The vaccinated group included patients who were fully vaccinated 2 weeks before the start of the study period. Vaccine status was confirmed objectively using LINKS, a statewide immunization reporting network that can be accessed only by health care professionals. Race was included in our demographic comparison to identify potential disparities in vaccine access and acceptance. The primary outcome was development of severe or critical COVID-19 based on National Institutes of Health criteria.7 Severe illness is defined as SpO2 less than 94% on room air, PaO2/FiO2 ratio less than 300 mm Hg, respiratory rate greater than 30 breaths per minute, or lung infiltrates greater than 50%.7 Critical illness is defined as respiratory failure, septic shock, or multiple organ failure.7 Secondary outcomes included SARS-CoV-2 infection, supplemental oxygen requirement, intensive care unit admission, and use of adjunctive medical therapy. A secondary analysis of the cohort was performed, including those who were partially vaccinated. Student's t test, Wilcoxon rank sum test, χ2 test, Fischer exact test, and logistic regression were used when appropriate. P<.05 is considered statistically significant.


A total of 10,092 pregnant patients were included in the study. There were 1,332 vaccinated patients and 8,760 incompletely vaccinated or unvaccinated patients, a 13.2% vaccination rate. Younger age, lower body mass index (BMI, calculated as weight in kilograms divided by height in meters squared), current smoking, and race were associated with unvaccinated status (Table 1). Vaccinated patients had lower odds of severe or critical COVID-19 (0.08% vs 0.66%, adjusted odds ratio [aOR] 0.10, 95% CI 0.01–0.49) and COVID-19 of any severity (1.1% vs 3.3%, aOR 0.31, 95% CI 0.17–0.51) (Table 2). Despite the lack of statistical significance for secondary outcomes, the use of adjunctive medical therapy was rare for vaccinated patients, and no vaccinated patients needed supplemental oxygen or intensive care unit admission (Table 2). Additionally, in the unvaccinated group there was one maternal death secondary to COVID-19 complications and six stillbirths, three of which occurred in patients who had SARS-CoV-2 infection earlier in the gestation. There were a total of 1,536 vaccinated patients in the secondary analysis, which included both fully and partially vaccinated patients (n=204, 2% partial vaccination rate). When including all partially vaccinated patients who received any doses of the vaccine before the study, an association between vaccinated status and lower odds of severe or critical COVID-19 (0.07% vs 0.68%, aOR 0.08, 95% CI 0.004–0.40) and COVID-19 of any severity (1.1% vs 3.3%, aOR 0.30, 95% CI 0.17–0.48) remained.

Table 1.:
Demographics for Pregnant Patients With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection Between June 15, 2021, and August 20, 2021 (N=10,092)
Table 2.:
Clinical Outcomes for Pregnant Patients With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection Between June 15, 2021, and August 20, 2021 (N=10,092)


Our study shows an association between SARS-CoV-2 vaccination and lower odds of severe or critical COVID-19 and COVID-19 of any severity in pregnant patients during the Delta variant–predominant fourth surge of SARS-CoV-2. A possible limitation of our study is the lack of data on positive SARS-CoV-2 test results or treatment of SARS-CoV-2 infection performed outside of the Ochsner Health System, or both, within the study population. This study also identified a low vaccination rate among pregnant patients (13.2%); unvaccinated status was associated with younger age, current smoking, lower BMI, and race. As nationwide efforts to improve vaccination acceptance continue,8,9 it is vital for obstetricians and gynecologists to educate vulnerable populations on the potential benefits of the SARS-CoV-2 vaccine in preventing severe or critical illness.


1. Centers for Disease Control and Prevention. Delta variant: what we know about the science. Accessed August 19, 2021.
2. Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S, et al. Effectiveness of Covid-19 vaccines against the B.1.617.2 (Delta) variant. N Engl J Med 2021;385:585–94. doi: 10.1056/NEJMoa2108891
3. Rosenberg ES, Holtgrave DR, Dorabawila V, Conroy M, Greene D, Lutterloh E, et al. New COVID-19 cases and hospitalizations among adults, by vaccination status-New York, May 3-July 25, 2021. MMWR Morb Mortal Wkly Rep 2021;70(37):1306–11. doi: 10.15585/mmwr.mm7034e1
4. Tenforde MW, Self WH, Naioti EA, Ginde AA, Douin DJ, Olson SM, et al. Sustained effectiveness of Pfizer-BioNTech and Moderna vaccines against COVID-19 associated hospitalizations among adults – United States, March-July 2021. MMWR Morb Mortal Wkly Rep 2021;70:1156–62. doi: 10.15585/mmwr.mm7034e2
5. Thompson MG, Burgess JL, Naleway AL, Tyner H, Yoon SK, Meece J, et al. Prevention and attenuation of Covid-19 with the BNT162b2 and mRNA-1273 vaccines. N Engl J Med 2021;385:320–9. doi: 10.1056/NEJMoa2107058
6. Zambrano LD, Ellington S, Strid P, Galang RR, Oduyebo T, Tong VT, et al. Update: characteristics of symptomatic women of reproductive age with laboratory-confirmed SARS-CoV-2 infection by pregnancy status – United States, January 22-October 3, 2020. MMWR Morb Mortal Wkly Rep 2020;69:1641–7. doi: 10.15585/mmwr.mm6944e3
7. National Institutes of Health. Coronavirus disease 2019 (COVID-19) treatment guidelines. Accessed September 16, 2021.
8. Society for Maternal-Fetal Medicine. SMFM: provider considerations for engaging in COVID-19 vaccine counseling with pregnant and lactating patients. Accessed September 29, 2021.
9. American College of Obstetricians and Gynecologists. Practice advisory: COVID-19 vaccination considerations for obstetric–gynecologic care. Accessed September 29, 2021.

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