On October 7, 2022, the Food and Drug Administration (FDA) approved a vaccine to be taken by women in their third trimester of pregnancy to prevent the highly contagious respiratory illness pertussis (whooping cough) in infants less than 2 months. Boostrix (Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine, Adsorbed) is the 1st vaccine licensed particularly for usage during pregnancy for preventing disease in young neonates whose mothers have been immunized during pregnancy.

Pertussis is a commonly encountered respiratory illness that frequently breaks out. Due to the "whooping" sound a person produces when gasping for air after coughing, the illness is also known as whooping cough.  All age groups are susceptible to pertussis. The risk of pertussis infection and significant complications in infants is higher. The majority of fatalities, hospitalizations, and severe pertussis cases affect infants under 2 months of age who are very young to get the childhood pertussis vaccination series as protection.

Centers for Disease Control and Prevention (CDC) estimated that in 2021, 4.2% of all pertussis cases recorded were in infants < 6 months, and that 31% of those cases necessitated hospitalization. When the Boostrix vaccination is administered during pregnancy, it increases the mother's antibodies, which are passed on to the unborn child. The FDA first gave Boostrix approval in 2005 as a single dose for booster vaccination against pertussis, diphtheria, and tetanus in people aged 10-18 years.

Later, the FDA also gave Boostrix approval for use in people aged 19 and older and for use with a second dose administered nine years or more after the first Tdap vaccination. The CDC has advised getting Tdap shots throughout pregnancy's third trimester since 2012. Based on the re-assessment of the Boostrix-relevant data from an observational case-control trial on efficacy of Tdap vaccine, the efficacy of Boostrix administered during 3rd trimester to prevent pertussis across infants less than 2 months of age was determined. These real-world statistics were deemed by the FDA to be real-world evidence in favor of this approval.

In this re-analysis, data from 108 pertussis cases in newborns under two months of age, incorporating 4 cases in which the mothers were given Boostrix during 3rd trimester, and 183 control newborns without pertussis, incorporating 18 whose mothers were given Boostrix during 3rd trimester, led to a preliminary estimate of Boostrix's effectiveness as a pertussis preventive that was 78% effective when given during the third trimester.

With the aid of information from published observational studies, the preliminary estimate of efficacy was revised. Estimates of efficacy from these statistical studies were in line with the preliminary estimate of 78%. In a randomized, placebo-controlled trial, using a non-U.S. version of Boostrix, the safety of Boostrix administration was evaluated during the 3rd trimester of pregnancy. The non-U.S. version of Boostrix comprises the same components as the U.S. formulation, with the exception that it contains more aluminium per dose. Hence, the FDA believes the safety data concerning this formulation is pertinent.

A total of 680 pregnant women participated in the trial, of whom 340 got Boostrix in its non-U.S. version and 340 were given a saline placebo. Following childbirth, the placebo patients received the Boostrix vaccine (non-U.S.). The rates of adverse effects reported after taking the non-U.S. version of Boostrix during pregnancy were similar to the rates after giving the non-U.S. version of Boostrix to research participants following childbirth.

No negative vaccine-related effects on pregnancy or the fetus/newborn were reported in the research. In earlier clinical investigations, those who received Boostrix most frequently complained of gastrointestinal issues, exhaustion, headache, redness at the injection site, and pain. The recommended dosage for Boostrix is a single 0.5-mL dose.