The US FDA recently approved Boostrix, a vaccine to be administered during the third trimester of pregnancy to prevent pertussis (whooping cough) in infants below two months of age. Boostrix is Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine, Adsorbed (Tdap).^1,2

The Boostrix Tdap vaccine is already approved for immunization of pregnant women to protect them against pertussis. CDC recommends that all pregnant women receive a Tdap vaccine during the 27th through 36th week of pregnancy, preferably during the earlier part of this time period. But for the first time this new indication for use in pregnancy is specifically to prevent pertussis in infants aged 2 months or younger. 

The vaccine was first approved in 2005, as a booster against tetanus, diphtheria and pertussis, for adolescents aged 10-18 years. The approval was later expanded to include persons aged ≥19 years. An additional dose ≥9 years after the initial dose of a Tdap vaccine was also approved.

Boostrix is administered in a single dose of 0.5-mL. 

The approval of the vaccine was based on reanalysis of data from an observational study, which examined data of 108 infants aged ≤2 months who developed pertussis and 183 infants who did not. Four mothers in the pertussis group were administered the Boostrix vaccine during the third trimester, while in the control group 18 mothers were vaccinated during the third trimester. The effectiveness of the vaccine in preventing pertussis among infants younger than 2 months of age, when administered during the third trimester of pregnancy was found to be 78%.1,2

The safety of the vaccine was investigated in a randomized placebo-controlled trial involving 680 pregnant women. Half of the women were given the vaccine during the third trimester, while the other half, who were administered a saline placebo during pregnancy, received the vaccine after childbirth. Both the groups had similar rates of adverse events. No adverse maternal and/or fetal effects of the vaccine were noted in the trial.1,2

References

1. FDA news release. https://www.fda.gov/news-events/press-announcements/fda-approves-vaccine-use-during-third-trimester-pregnancy-prevent-whooping-cough-infants-younger-two, October 07, 2022.
2. Rubin R. Vaccine approved in pregnancy to protect young infants. JAMA. 2022 Nov 15;328(19):1898. doi: 10.1001/jama.2022.1847.