Monovalent Acellular Pertussis Vaccine Safe and Effective for Neonates With Mothers Unvaccinated for Tdap

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The acellular pertussis vaccine is safe and immunogenic when administered to neonates whose mothers did not receive Tdap vaccine during pregnancy.
The acellular pertussis vaccine is safe and immunogenic when administered to neonates whose mothers did not receive Tdap vaccine during pregnancy.

If licensed and available, the monovalent acellular pertussis (aP) vaccine is safe and effective in newborns whose mothers did not receive the tetanus toxoid, reduced diphtheria toxoid, and pertussis antigen (Tdap) vaccine, according to a study published in JAMA Pediatrics.

A group of investigators from Australia conducted a randomized, nonblinded phase 3 clinical trial of the administration of monovalent aP vaccine to neonates. The purpose of the study was to compare the immunoglobulin G (IgG) antibody responses to vaccine antigens in those receiving both aP vaccine within 5 days of birth and hepatitis B (HBV) vaccine with the responses of those receiving only HBV vaccine.

Infants also received a hexavalent vaccine at 6, 16, and 24 weeks that included pediatrically formulated diphtheria, tetanus, and pertussis antigens, Haemophilus influenzae type b (Hib), HBV, and polio vaccine, as well as a 10-valent pneumococcal conjugate vaccine.

The main outcome was the proportion of newborns with IgG antibody to both pertussis toxin (PT) and pertactin (PRN) at a concentration of more than 5 enzyme-linked immunosorbent assay units per milliliter (ELU/mL) at 10 weeks.

The secondary outcome was a comparison of IgG antibody response to PT, PRN, and filamentous hemagglutinin (FHA) at 6, 24, and 32 weeks between infants receiving aP/HBV vaccination and infants receiving only HBV vaccination, stratified by confirmed maternal Tdap vaccination or pertussis infection.

Healthy infants born at 36 weeks' gestation or later (median weeks of gestation, 39.2) were eligible for inclusion in the study (n = 440). The HBV vaccine was administered to all infants. After the maternal Tdap history had been recorded, the infants were randomly assigned either to receive the aP vaccine in addition to the HBV vaccine (n=221) or not (n=219).

When available sera from 206 infants in the aP vaccine group and 193 infants in the control group were analyzed at 10 weeks, PT and PRN antibodies were detectable in 93.2% of the 206 infants who received both the aP and HBV vaccine and in 50.8% of the 193 infants who received only the HBV vaccine.

At 24 weeks, significantly higher levels of IgG antibody to PT and FHA were reported in infants in the aP vaccine cohort compared with infants in the control cohort, regardless of maternal Tdap vaccination status, although at 32 weeks, levels were significantly higher only for specific subgroups of PT and FHA. At 32 weeks, all infants who had received the aP vaccine at birth (181 with sera available for testing) had detectable PT IgG and significantly lower mean IgG geometric average concentrations for Hib, HBV, diphtheria, and tetanus antibodies.

Adverse events were similar in both groups at each time point.

“Although receipt of Tdap during pregnancy is the current recommended strategy, administration of the aP vaccine at birth has the potential to reduce the risk of death and severe morbidity from Bordetella pertussis infection in the first 2 months of life among infants whose mothers did not receive Tdap during pregnancy,” the authors wrote.

“Availability of a monovalent acellular pertussis vaccine has the potential to be valuable in maternal programs in high-income countries (where tetanus and diphtheria boosting is not needed) and would also facilitate the option of neonatal vaccination,” concluded the investigators.

Reference

Wood N, Nolan T, Marshall H, et al. Immunogenicity and safety of monovalent acellular pertussis vaccine a birth: a randomized clinical trial [published online September 10, 2018]. JAMA Pediatr. doi:10.1001/jamapediatrics.2018.2349
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