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Since its implementation 12 years ago, the maternal tetanus, reduced diphtheria, and acellular pertussis (Tdap) vaccine has contributed to a decrease in pertussis among the youngest infants.

Following the implementation of the maternal vaccine, incidence of pertussis decreased in infants under age 2 months from 205.4 per 100,000 infants in 2012 to 75.4 cases per 100,000 in 2016. During the final years of the analyzed post-maternal vaccination implementation period, the incidence of pertussis was stable at 80.9 cases per 100,000 infants from 2017 to 2019.

In comparison, the pre-maternal Tdap vaccine period had no significant changes for annual pertussis incidence, which stayed around 165.3 per 100,000 infants. The average annual pertussis incidence rate during the entire post-maternal vaccination period was 121.8 cases per 100,000 infants, a net decrease in overall pertussis cases, reported Tami Skoff, MS, and colleagues of the CDC in Atlanta, in .

Pertussis disease is a highly contagious respiratory illness that often requires hospitalization. The Tdap vaccine is not recommended for children before age 2 months, leaving newborns susceptible to disease during the early months of life unless they are protected through a maternal Tdap vaccine, such as the recently approved Boostrix. Of the pertussis cases in infants younger than age 1 year from 2000 to 2019, a full third occurred among those under age 2 months, Skoff's group reported.

A maternal Tdap vaccine started being endorsed by the Advisory Committee on Immunization Practices (ACIP) for pregnant women in 2011 and has since been recommended for all women during every pregnancy from .

"Getting Tdap during pregnancy offers infants the best protection before they are old enough to receive their whooping cough vaccines," said José Romero, MD, director of CDC's National Center for Immunization and Respiratory Diseases, in a press release. "This protection is critical because those first few months are when infants are most likely to have serious complications, be hospitalized or die if they get whooping cough."

Yet maternal Tdap vaccination coverage is in decline: recent CDC data show that Tdap from the 2020-2021 to the 2021-2022 season. Broken down by race, Black non-Hispanic women were the only group to increase their vaccine rates from 2021 to 2022. In an April 2022 survey, more than half of participants said they did not receive a Tdap vaccination during pregnancy from October 2021 to January 2022.

Skoff's group highlighted the importance of informing practitioners involved in pregnancy about maternal Tdap vaccination following resurgences of whooping cough.

"Efforts should continue to place emphasis on increasing Tdap vaccination uptake through education of prenatal care practitioners and other key practitioners who may routinely interact with pregnant women in their practices, such as pediatricians and family practice physicians," the CDC investigators wrote.

"As a health care practitioner recommendation is a factor associated with vaccination during pregnancy, it is important for these practitioners to clearly state their recommendation for vaccination and to communicate the benefits and risks of vaccination as well as listen to and respond directly to pregnant patients' questions," they added.

The study relied on case data reported through the National Notifiable Diseases Surveillance System from 2000 to 2019.

Pertussis was defined as cough of 2 weeks or longer duration with paroxysms, inspiratory whoop, or posttussive vomiting. Both lab-confirmed cases and clinical cases without laboratory confirmation or epidemiologic linkage were included in the analysis.

Older infants (ages 6 months to under a year) had a relatively stable 19.7 pertussis cases per 100,000 infants during the pre-maternal Tdap vaccination period. Since then, these children have seen no significant changes in pertussis incidence either.

Limitations to the study include missing data regarding patient vaccination history at the individual level, according to Skoff and colleagues.

"Everyone who is pregnant should feel confident in knowing that the Tdap vaccine is safe and effective," said Linda Eckert, MD, American College of Obstetricians and Gynecologists' liaison to ACIP, in a statement. "Knowing that Tdap vaccination during pregnancy protects nine in 10 babies from being hospitalized with whooping cough, I strongly recommend this vaccine to all my pregnant patients for their peace of mind and for their family's health and well-being."

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