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Vaccines (Basel). 2020 Mar 11;8(1). pii: E124. doi: 10.3390/vaccines8010124.

Safety of Administering Live Vaccines During Pregnancy: A Systematic Review and Meta-Analysis of Pregnancy Outcomes.

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Hospital Infantil de México Federico Gómez, Mexico 06720, Mexico.
London School of Hygiene and Tropical Medicine (Alumni), London WC1E 7HT, UK.
Compañeros en Salud-Partners in Health México, Mexico 11800, Mexico.
Instituto Tecnológico y de Estudios Superiores de Monterrey, Mexico 14380, Mexico.
Disease Control Elimination Theme, MRC Unit The Gambia at the London School of Hygiene and Tropical Medicine, P.O. Box 273, Banjul, Gambia.
The Vaccine Centre, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
Vaccines & Immunity Theme, MRC Unit the Gambia at the London School of Hygiene and Tropical Medicine, P.O. Box 273, Banjul, Gambia.


Live-attenuated vaccines (LAV) are currently contraindicated during pregnancy, given uncertain safety records for the mother-infant pair. LAV might, however, play an important role to protect them against serious emerging diseases, such as Ebola and Lassa fever. For this systematic review we searched relevant databases to identify studies published up to November 2019. Controlled observational studies reporting pregnancy outcomes after maternal immunization with LAV were included. The ROBINS-I tool was used to assess risk of bias. Pooled odds ratios (OR) were obtained under a random-effects model. Of 2831 studies identified, fifteen fulfilled inclusion criteria. Smallpox, rubella, poliovirus, yellow fever and dengue vaccines were assessed in these studies. No association was found between vaccination and miscarriage (OR 0.98, 95% CI 0.87-1.10), stillbirth (OR 1.04, 95% CI 0.74-1.48), malformations (OR 1.09, 95% CI 0.98-1.21), prematurity (OR 0.99, 95% CI 0.90-1.08) or neonatal death (OR 1.06, 95% CI 0.68-1.65) overall. However, increased odds of malformations (OR 1.24; 95% CI 1.03-1.49) and miscarriage after first trimester immunization (OR 4.82; 95% CI 2.38-9.77) was found for smallpox vaccine. Thus, we did not find evidence of harm related to LAV other than smallpox with regards to pregnancy outcomes, but quality of evidence was very low. Overall risks appear to be small and have to be balanced against potential benefits for the mother-infant pair.


live attenuated vaccines; pregnancy outcomes; pregnant women; safety

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