Whooping cough shots cut young kids’ odds of getting sick by 96%, state says

Young children who'd had at least three doses of the whooping cough vaccine were about 96% less likely to come down with a confirmed case during Alaska's record 2024 outbreak, state Department of Health researchers reported Thursday in a CDC journal.

The outbreak was the worst on record in Alaska. From April 2024 to April 2025, the state counted 679 confirmed and probable cases, compared with an average of 13 a year from 2019 to 2023, according to a state bulletin. Twenty-nine people were hospitalized, 18 of them babies under a year old. One unvaccinated infant died.

The new study, published in the CDC's Morbidity and Mortality Weekly Report, looked at children from 6 months to 6 years old. Most of the sick kids in it had never been vaccinated. Of 84 children with confirmed whooping cough, 52 had no doses. Only 21 were fully vaccinated.

To see whether that was unusual, the researchers compared the sick children with 229 kids the same age who came into the same 17 health care facilities with a cough and were tested for respiratory viruses. In that group, only about 1 in 8 were unvaccinated, and more than 3 in 4 were fully vaccinated.

From that comparison, the researchers estimated that three or more doses cut a child's odds of a confirmed case by about 96%. Children with one or two doses were also protected, by about 85%.

The vaccine, called DTaP, also protects against diphtheria and tetanus. It's given as shots at 2, 4 and 6 months, with boosters at 15 to 18 months and 4 to 6 years. The authors said their findings support the national recommendation to start the shots at 2 months.

Whooping cough was rare in Alaska before the outbreak. The state's rate was 0.27 cases per 100,000 people in 2022 and a record 83 per 100,000 in 2024. DTaP coverage among young Alaska children was below the national average in 2022 and 2023, and the authors wrote that declining coverage "might have contributed to the size of the 2024 outbreak." Only 55% of Alaska toddlers had completed the recommended childhood vaccines, Alaska News reported in July.

The study has limits. It counted only lab-confirmed cases, so it can't say whether the shots made illness milder. It may have missed patients at the smallest clinics, and its findings may not apply to older children. It also didn't look at vaccination during pregnancy, which the state says is the only protection for babies too young for their first shot.

An earlier state analysis of the same outbreak, covering children up to 17, put protection for fully vaccinated kids at about 93%.

When the CDC changed the national childhood vaccine schedule Jan. 26, it left the routine recommendations for DTaP and Tdap, the booster for older kids and adults, unchanged, a February state bulletin said. Eligible children can get the shots free through federal and state programs.