Vaccination provides effective protection against increased risk of pregnancy complications due to COVID-19 Omicron variant

The global network led by the Oxford Maternal and Perinatal Health Institute (OMPHI) at the University of Oxford, which included Robert Gunier, Stephen Rauch, and Brenda Eskenazi at the UC Berkeley School of Public Health’s Center for Environmental Research and Community Health (CERCH), has published new research in The Lancet that showed that vaccination is an effective protection against the increased risk of pregnancy complications from the COVID-19 Omicron variant.

The paper presents results of the “2022 INTERCOVID Study,” conducted in 41 hospitals across 18 countries. To evaluate the impact of the COVID-19 Omicron variant on maternal and neonatal outcomes the researchers studied 1,545 pregnant women diagnosed with the variant and 3,073 non-diagnosed, concomitant pregnant women as controls. The study was conducted between 27 November, 2021, and 30 June, 2022, during which time Omicron was the variant of concern. Vaccine effectiveness against the variant was also assessed.

The COVID-19 Omicron variant during pregnancy was associated with increased risks of maternal morbidity, severe pregnancy complications, and hospital admission, especially among symptomatic and unvaccinated women. In particular, the risk of preeclampsia was increased among women with severe symptoms. Obese/overweight women with severe symptoms were at the highest risk for maternal morbidity and severe complications.

Vaccinated women were well protected against severe COVID-19 symptoms and complications and had a very low risk of admission to an intensive care unit. Prevention of severe COVID-19 symptoms and complications requires women to be completely vaccinated, preferably with a booster dose as well.

In the study, mRNA vaccines were most effective in preventing severe COVID-19 symptoms and complications, although viral vector vaccines with a booster also provided adequate protection – for at least 10 months after the last dose for both mRNA vaccines and viral vector vaccines with a booster.

“In this multinational study, there was no evidence of an increased risk of pregnancy complications or adverse perinatal events associated with COVID-19 vaccines, even if the first vaccination was received during pregnancy,” said Robert Gunier, associate researcher at UC Berkeley School of Public Health’s Center for Environmental Research and CommunityHealth (CERCH) and lead statistician on the paper. “Unvaccinated pregnant women with a COVID-19 diagnosis while Omicron was the variant of concern had more than three times the risk of severe complications compared to unvaccinated women without a COVID-19 diagnosis. COVID-19 vaccines were highly effective at preventing severe symptoms and complications when pregnant women were completely vaccinated (>70% effectiveness) or had a booster vaccination (>90% effectiveness).”

“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. Antenatal services worldwide should strive to include vaccination against COVID-19 in the routine care of pregnant women,” said José Villar, Professor of Perinatal Medicine at the University of Oxford, who co-led INTERCOVID 2022.

Read the full paper in The Lancet.


In addition to researchers at the University of Oxford and The Center for Environmental Research and Community Health (CERCH) at UC Berkeley School of Public Health (Robert B. Gunier, Stephen Rauch MPH, and Brenda Eskenazi), other co-authors include dozens of researchers at Nuffield Department of Women’s Reproductive Health; Division Neonatología, Hospital Materno Infantil Ramón Sarda, Buenos Aires, Argentina; Department of Paediatrics and Child Health, The Aga Khan University Hospital, Karachi, Pakistan; Vita-Salute San Raffaele University and IRCCS San Raffaele Scientific Institute, Obstetrics and Gynaecology Department,Milan, Italy; Department of Clinical Sciences and Community Health, University of Milan, NICU, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy; Unit of Obstetrics and Gynecology, L- Sacco Hospital ASST Fatebenefratelli Sacco, Department of Biological and Clinical Sciences, University of Milan, Milan, Italy; Department of Obstetrics and Gynecology, Sancaktepe Sehit Prof Dr Ilhan Varank Training and Research Hospital, University of Health Sciences, Istanbul, Türkiye; Neonatal Care Unit, Department of Public Health and Pediatrics, School of Medicine, University of Turin, Italy; Instituto de Investigación Sanitario de Aragón (IIS Aragon), Hospital Clínico Universitario Lozano Blesa Zaragoza, Spain; Department of Pediatrics, Gynecology & Obstetrics, Hôpitaux Universitaires de Genève, Geneva, Switzerland; Instituto Nacional de Perinatología Isidro Espinosa de los Reyes, Mexico City, Mexico; Children’s Hospital V Buzzi,ASST Fatebenefratelli Sacco, Milan, Italy; Elizabeth Garrett Anderson Institute for Women’s Health, University College London, London, UK; Fetal Medicine Unit, University College London Hospitals NHS Foundation Trust, London, UK; Maternal-Fetal Medicine Unit, Department of Obstetrics and Gynecology, Hospital Universitari Vall d’Hebron, Vall d’Hebron, Barcelona Hospital Campus, Universitat Autonoma de Barcelona, Barcelona, Spain; Centro Hospitalario Pereira Rossell, Montevideo, Uruguay; Tufts Medical Center, Boston; Department of Obstetrics and Gynecology, Hôpitaux Universitaires de Strasbourg, Strasbourg, France; Servicio de Neonatologia, Hospital Italiano de Buenos Aires, Instituto Universitario Hospital Italiano, Buenos Aires, Argentina; Ann and Robert H Lurie Children’s Hospital of Chicago; Maternal and Child Department, Hospital Nacional Profesor Alejandro Posadas, Buenos Aires, Argentina; Hôpital Universitaire Necker-Enfants Malades, Paris, France; Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; Department of Clinical Nutrition and Dietetics, College of Health Sciences, University of Sharjah, Sharjah, United Arab Emirates; Departments of Obstetrics and Gynecology and of Global Health, University of Washington, Seattle, WA; Hospital Universitário da Universidade Federal do Maranhão, São Luís, Maranhão, Brazil; Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina; Department of Obstetrics and Gynecology, Bordeaux University Hospital, Bordeaux, France; Brigham and Women’s Hospital, Harvard Medical School; Servicio de Neonatología del Departamento Materno Infantil, Hospital Universitario Austral, Buenos Aires, Argentina; St George’s University Hospitals NHS Foundation Trust, London; Hospital Julio C Perrando, Resistencia, Chaco, Argentina; Clínica y Maternidad Suizo Argentina, Buenos Aires, Argentina; Medical Faculty Universitas Airlangga – Dr Soetomo General Academic Hospital, Surabaya, Indonesia; Obstetrics and Gynecology Division-Hadassah Medical Center Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel; Department of Obstetrics and Gynecology, The Jikei University School of Medicine, Tokyo, Japan; Sanatorio Otamendi, Buenos Aires, Argentina; Ascension–Resurrection Medical Center, Chicago; Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo; General Hospital With Extended Activity Prilep, Prilep, North Macedonia; Department of Obstetrics and Gynaecology, College of Medical Sciences, Gombe State University, Gombe, Nigeria; College of Medicine, University of Ibadan and University College Hospital, Ibadan, Nigeria; University of Nottingham, University of Nottingham Medical School, Nottingham, UK; Center for Global Child Health, Hospital for Sick Children, Toronto, Canada.

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