Safety surveillance of respiratory syncytial virus (RSV) vaccine among pregnant individuals: a real-world pharmacovigilance study using the Vaccine Adverse Event Reporting System.

Similarly, Pfizer’s two maternal RSV vaccine trials, which excluded pregnant individuals at increased risk of preterm delivery, also reported a numerical increase in preterm births, although the findings did not reach statistical significance. 8 Pfizer’s phase 2b trial reported six preterm births out of 114 pregnancies (5.3%) in the vaccine group and 3 out of 116 (2.6%) in the placebo group. 12 In the subsequent phase 3 trial, preterm births were reported in 5.7% (202/3568) of infants born to vaccinated mothers compared with 4.7% (169/3

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