MRNA Moderna Inc

By Sarah Toy 

The World Health Organization released new guidance about Moderna Inc.'s Covid-19 vaccine this week, recommending generally against the use of the vaccine during pregnancy except in those at high risk of exposure or having a severe case.

"In the interim, WHO recommends not to use mRNA-1273 in pregnancy, unless the benefit of vaccinating a pregnant woman outweighs the potential vaccine risks, such as in health workers at high risk of exposure and pregnant women with co-morbidities placing them in a high-risk group for severe Covid-19," the guidance said. The agency said its recommendations would be updated as more data become available.

The recommendation echoes guidance for Pfizer Inc. and BioNTech SE's vaccine released earlier this month. The WHO said it doesn't recommend pregnancy testing before vaccination, nor does it recommend delaying pregnancy following vaccination. The WHO does recommend that lactating women be offered the vaccines, saying that the shots are unlikely to pose a risk to breast-feeding children.

Covid-19 mRNA vaccines aren't made from live virus, and the mRNA, or messenger RNA -- named after the molecular couriers that deliver genetic instructions -- doesn't itself enter the cell's nucleus and is degraded quickly, the WHO said. Developmental and reproductive toxicology studies in animals haven't shown any harmful effects, the WHO added.

At the same time, there aren't enough data on actual pregnant people to assess the vaccine's effectiveness or risk in pregnancy, the agency said. Pregnant women should be given information and counseling on the lack of safety and efficacy data, it said.

Neither Moderna nor Pfizer enrolled pregnant women in their Covid-19 vaccine trials. Moderna says it plans to establish a registry to study pregnancy outcomes in mothers and infants. Pfizer says it intends to start a maternal vaccine study in the future.

Research has shown that pregnant women are at higher risk of having a severe case of Covid-19 than those who aren't pregnant, and Covid-19 may be associated with a higher risk of preterm delivery. The Centers for Disease Control and Prevention says pregnant people may choose to be vaccinated if they wish, adding that a conversation with a patient's clinical team can help.

Write to Sarah Toy at sarah.toy@wsj.com

(END) Dow Jones Newswires

January 27, 2021 14:33 ET (19:33 GMT)

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