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Three doses of an mRNA vaccine provides greater protection for pregnant women against moderate to severe COVID-19 infection with the Omicron variant

Published on Wednesday, 31 August 2022 Tweet

Researchers at the National Perinatal Epidemiology Unit, part of Oxford Population Health, have found that most pregnant women with moderate to severe COVID-19 infection who were admitted to hospital during the Omicron variant's dominant period were unvaccinated or had received fewer doses than the current guidance recommends.

The study also found that the severity of the infection decreased with vaccination, with no intensive care admissions among women who had received three vaccine doses.

In the UK from April 2021, mRNA vaccines1 were recommended for pregnant women. In December 2021, pregnant women were recognised as a risk group with priority for vaccination and advised to take at least two doses and to have a third (booster) dose 12 weeks after the second.

Using UK Obstetric Surveillance System data from 3699 women admitted to all 194 hospitals in the UK with a consultant-led maternity unit, the researchers found that 1 in 5 unvaccinated pregnant women who were admitted to hospital with symptoms of COVID-19 between 15 December 2021 and 14 March 2022 suffered moderate to severe disease. This figure reduced to 1 in 20 for women who had three doses at the time of admission. Among the 30 women admitted to an intensive care unit, 23 were unvaccinated.

The results of the study indicated that the most current cases of respiratory failure among pregnant women are preventable yet vaccine uptake among pregnant women remains low.

Marian Knight, Professor of Maternal and Child Population Health at Oxford Population Health and lead researcher, said 'Pregnant women have a greater risk of severe outcomes from COVID-19, but the vaccination protects both the woman and her baby. This study shows the importance of both taking the vaccine and keeping up with the recommended booster schedule as new variants of the virus emerge.'

The full report is published today in BMJ Medicine.

Hilde Engjom, co-author and researcher from The Norwegian Institute of Public Health adds: “this study shows that investing in robust surveillance of the impact on health in pregnancy is important as new variants of the coronavirus emerge. Such surveillance play a key role in providing pregnant women and women planning a pregnancy with better knowledge about how to protect herself and the baby.

1 Many vaccines use a weakened or inactivate virus to trigger an immune response. Messenger RNA (mRNA) vaccines teach our cells how to make a protein that triggers an immune response and enables us to make antibodies. mRNA COVID-19 vaccines do not use any live virus, and cannot cause COVID-19 infection. mRNA COVID-19 vaccines have been shown to be safe for pregnant women.

Updated: Wednesday, 31 August 2022 10:42 (v1)