key: cord-0998712-16svki2l
authors: Magee, Laura A; von Dadelszen, Peter; Kalafat, Erkan; Duncan, Emma L; O'Brien, Pat; Morris, Edward; Heath, Paul; Khalil, Asma
title: COVID-19 vaccination in pregnancy—number needed to vaccinate to avoid harm
date: 2021-11-02
journal: Lancet Infect Dis
DOI: 10.1016/s1473-3099(21)00691-5
sha: a7fab11a48d9c2d8927a7f83fa430296f9df179d
doc_id: 998712
cord_uid: 16svki2l

nan

. łWe used a SARS-CoV-2 infection rate ranging from 2% 1 to 10%, with symptoms estimated to occur in 27% of those infected. The risk of severe maternal COVID-19 was estimated by a living systematic review 1 . Risks of pregnancy complications were based on a UK national population-based cohort study 6 . Vaccination effectiveness was based on observational data in pregnancy and adverse effects on postmarketing surveillance 2, 4 . Calculations of NNV are based on 90% effectiveness of vaccination against SARS-CoV-2 infection, based on mRNA vaccines. † This is a combination of iatrogenic and spontaneous preterm birth, some of which is unavoidable. ǂ This is based on 6 studies from 4 countries and >40,000 pregnant women 1 . ǁ Serious adverse events were defined as any untoward medical occurrence that resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, or resulted in persistent disability/incapacity. The proportions of participants who reported at least 1 serious adverse event were 0.6% in the vaccine group and 0.5% in the placebo group. Two serious adverse events were considered by U.S. Food and Drug Administration as possibly related to vaccine: shoulder injury possibly related to vaccine administration or to the vaccine itself, and lymphadenopathy involving the axilla contralateral to the vaccine injection site. Otherwise, occurrence of severe adverse events involving system organ classes and specific preferred terms were balanced between vaccine and placebo groups. 7 § This is with the viral vector vaccines, but women of child-bearing age in the UK are recommended to receive mRNA vaccines (i.e, Pfizer or Moderna). 8 

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