Three DTaP doses cut children’s whooping cough risk by 96% during Alaska outbreak

CDC research from an Alaska outbreak found that children who completed the primary DTaP series were 26 times less likely to develop laboratory-confirmed pertussis than unvaccinated children.

A new study from the US Centres for Disease Control and Prevention suggests the childhood vaccine against whooping cough offers strong protection for young children, even during an outbreak. The research, published in the agency’s Morbidity and Mortality Weekly Report, found that children in Alaska who had received at least three doses of the DTaP vaccine were 96.2% less likely to develop laboratory-confirmed pertussis than unvaccinated children.

The study examined cases from a statewide outbreak in Alaska between May and November 2024, looking at children aged six months to six years. According to the CDC analysis, children who had not been vaccinated were around 26 times more likely to test positive for pertussis than those who had completed the three-dose primary series. Even partial vaccination appeared to help: children who had received one or two doses had an estimated protection rate of 85.3%.

Joseph McLaughlin, the study’s lead author and an epidemiologist with the Alaska Department of Health in Anchorage, said the findings reinforce the value of immunisation for younger children. The CDC recommends five DTaP doses during childhood, beginning at two months of age, with the final dose usually given between ages four and six. Earlier CDC guidance has also described the full series as highly effective, although protection can decline over time after the final dose.

Whooping cough, also known as pertussis, is a highly contagious respiratory infection caused by Bordetella pertussis. It often begins like a common cold, with a runny nose, sneezing and a mild cough, before progressing to severe coughing fits that can last for weeks. Some patients develop the characteristic “whoop” as they gasp for breath, while others, especially infants, may simply struggle to breathe.

The illness can be particularly dangerous for babies, especially those younger than six months, whose immune systems are still developing. In young infants, the infection may not produce the classic coughing pattern and can instead show up as feeding difficulties or brief pauses in breathing, making it harder to recognise quickly. Severe cases can lead to pneumonia, seizures, brain injury and death. According to the CDC, 16 people in the United States died from whooping cough in 2025, including 10 infants.

The findings come against a backdrop of falling childhood vaccination coverage in the United States. CDC data show DTaP uptake among kindergarten children fell to 92% in the 2025-2026 school year, down from 95.2% in 2017-2018. Public health experts have long warned that lower vaccination rates make it easier for pertussis to spread, particularly among children who are too young to be fully protected.

Doctors can diagnose pertussis by testing samples from the nose or throat, and early treatment matters most for infants, who can deteriorate quickly. Health officials say parents should seek medical advice promptly if a child develops a persistent cough, breathing problems or repeated vomiting after coughing, particularly if the child is not fully vaccinated.