Study: Maternal pertussis vaccination prevents most infant infections
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Key takeaways:
- The effectiveness of maternal pertussis vaccination declined from 70.4% at 2 months to 43.3% at 7 to 8 months.
- Tdap immunization rates during pregnancy in Australia, the U.K. and U.S. are between 50% and 60%.
Maternal pertussis vaccination resulted in a 66% decrease in pertussis among infants through age 6 months and remained protective for up to 8 months, with no evidence it blunted response to further vaccination, an Australian study found.
Pertussis, commonly known as whooping cough, is primarily spread through droplets containing the bacterium Bordetella pertussis. The CDC recommends that children aged younger than 7 years receive five doses of DTaP (diphtheria-tetanus-acellular pertussis-containing vaccine) given at different intervals of age.
Researchers from the CDC, WHO and UNICEF reported last year ago that 25 million children worldwide were unvaccinated or incompletely vaccinated with Tdap.
One of the authors of the new study said their idea for the investigation came in 2015 while they were working in Western Australia.
“Pertussis can be really severe, and we unfortunately had a death in a 5-week-old baby in Western Australia,” Annette K. Regan, PhD, an assistant professor at the University of San Francisco School of Nursing and Health Professions, told Healio. “We had started to notice a nationwide increase in protective infant pertussis cases, and we knew that we wanted to implement a program that could help prevent these severe infections.”
Before this, Regan said, the researchers used a strategy called “cocooning,” in which once the infant was born, their parents, grandparents and any other close family members would be given Tdap vaccinations, but a previous evaluation showed that this strategy was not effective.
“Pertussis is a low-incidence disease,” Regan said. “It's not very common, but we're very worried about it because when it does happen, it can be very bad. But because it's not very common, that means you need really big datasets, usually to do a very detailed analysis like the ones that we were planning, and so we knew we needed a lot of mothers and their infants.”
Regan and colleagues reviewed data on 279,418 infants born to 252,444 mothers in three jurisdictions across Australia, 51.7% of whom received the vaccine through a maternal pertussis vaccination program, mostly at 28 to 31 weeks’ gestation. Among this group, vaccination was associated with a 66% overall decrease in infant pertussis infection through 6 months of age, the researchers reported.
The efficacy of maternal pertussis vaccination declined from 70.4% among infants aged younger than 2 months to 43.3% among infants aged 7 to 8 months and was not significant after 8 months of age, they found.
Additionally, although the researchers found that maternal pertussis vaccination might lower the effectiveness of an infant’s third Tdap shot, they did not observe evidence of higher rates of pertussis infection in those infants through 18 months of age.
“Any provider [who] could possibly be giving pertussis vaccines should feel reassured,” Regan said. “I'm hoping that these data will encourage more providers to be more proactive about providing these vaccines.”
In an accompanying commentary, Kathryn M. Edwards, MD, professor emeritus of pediatrics in the division of infectious diseases at Vanderbilt University School of Medicine, noted a recent report by the CDC that also showed a significant decrease in the incidence of pertussis following the introduction of maternal Tdap vaccination.
“As with the Australian data, the U.S. data support the overall benefit of the maternal Tdap program and as with the Australian data do not suggest that blunting has led to an increase in cases within the first year of life,” Edwards, who is a member of the Healio Pediatrics Peer Perspective Board, wrote.
“Despite these encouraging data demonstrating the important role of maternal immunization in reducing pertussis disease, Tdap immunization rates during pregnancy in Australia, the United Kingdom, and the United States remain between 50% and 60%,” she wrote. “Active engagement to increase these rates should be implemented.”
Edwards said the consequences of maternally derived antibodies on infant responses should continue to be monitored, as they were by Regan and colleagues.
“It will be critical to assess the burden of vaccine-preventable diseases and affirm that blunting from maternal immunization has no material impact on disease control,” Edwards wrote.
References:
Edwards K, et al. Pediatrics. 2023;doi:10.1542/peds.2023-063067.
Regan AK, et al. Pediatrics. 2023;doi:10.1542/peds.2023-062664.
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