(Bloomberg) -- Covid-19 vaccines using messenger RNA technology were safe in pregnancy according to a large Canadian survey, further building the case for pregnant women to get the shots.

Vaccinated women who weren’t pregnant reported higher rates of potential side effects than pregnant women, surprising researchers. In the survey, 7.3% of pregnant women who got an mRNA-based Covid shot reported potential side effects within a week after their second dose, most commonly feeling unwell, having a headache or migraine or a respiratory tract infection. About 11% of respondents who weren’t pregnant made similar reports.

Further research is needed into future mRNA vaccines to show whether the reduced side effects in pregnant people were due to the mRNA vaccine platform or potentially a feature of these particular shots, said Julie Bettinger, a vaccine safety scientist at the British Columbia Children’s Hospital Research Institute, and the study’s senior author. 

Pregnant women face an elevated risk of severe Covid, and Covid infections during pregnancy have been linked to a higher risk of complications.

The Canadian team focused on health outcomes within the first seven days after vaccination, though researchers said they’re continuing to follow up on the findings. Some 191,360 women completed a survey after their first vaccine dose, and 94,937 completed a survey after the second dose.

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