Recommending that pregnant women get a pertussis vaccination appears to decrease the incidence of infant pertussis, according to a recent study by Catherine Psaras of the University of California, Los Angeles (UCLA) and colleagues.¹ However, the recommendation for adult vaccination was not associated with a significant change in infant mortality from the disease.

Data are from the Centers for Disease Control and Prevention’s natality files and cover the period from January 2005 through December 2017.

Pertussis Deaths Are Concentrated Among Infants Who Cannot Be Vaccinated

Commonly known as whooping cough, pertussis is a contagious and potentially deadly respiratory disease. There are two types of combination vaccines that protect against pertussis: DTaP, which is given to infants and children under 7, and Tdap, given to older children and adults.

While most infections occur among adults, deaths are concentrated among infants under 2 months old. Because infants cannot get the DTaP vaccine until 2 months of age, maternal Tdap vaccination is the primary prevention strategy for infants.

In 2011, the Advisory Committee on Immunization Practices (ACIP) recommended the Tdap vaccine for pregnant people who had not recently been immunized. In 2012, it expanded this recommendation to include all pregnant people, regardless of previous vaccination status.

Infant Cases Drop in Years Following Maternal Vaccine Recommendations

The study included all pertussis cases reported to the Centers for Disease Control (CDC) through the National Notifiable Disease Surveillance System (NNDS) and cases of pertussis in which infants died, as captured by the CDC’s National Vital Statistics program. Local state and health departments report pertussis cases to the NNDS.

Between 2005 and 2017, nearly 40,000 pertussis cases occurred among infants in the United States. After the ACIP recommendations were announced, the annual rate of infant pertussis fell by 54 cases per 100,000 infants, Psaras and colleagues found. This finding is consistent with previous studies that have shown a decrease in pertussis among infants born to mothers who received the Tdap vaccine during pregnancy.

Of the 155 infant deaths from pertussis between 2005 and 2017, 38 occurred in the post-recommendations period. The researchers found no appreciable differences in infant pertussis mortality at the population-level following the expanded recommendations in 2012.

The researchers noted several possible explanations for the lack of effect on infant pertussis mortality. One theory is that that maternal immunization rates for Tdap may not be high enough to translate into decreased pertussis-related mortality among infants. Another possible explanation is that the mothers of the highest-risk infants are not being reached with the Tdap vaccine during pregnancy.

“Our findings reinforce the importance of maternal Tdap vaccination in protecting infants from pertussis. While the recommendations have successfully reduced overall infant pertussis cases, ensuring that all pregnant individuals—especially those in high-risk populations—receive the vaccine remains a critical public health priority,” Psaras said.

The authors conclude that pregnant women should receive the Tdap during every pregnancy in accordance with the ACIP recommendations to reduce the incidence of pertussis infections among infants and to increase the maternal Tdap immunization rate.

This article was produced under a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). The work of researchers from the NICHD-funded Population Dynamics Research Center at the University of California Los Angeles was highlighted.