New CDC Study: DTaP Was 96% Effective Against Whooping Cough in Young Kids — and Unvaccinated Children Had 26x the Odds of Catching It

Last updated: October 2026. This article is for general information and is not a substitute for personalised advice from your doctor, health visitor, or paediatrician. See our Editorial Policy.

Quick answer: A CDC report published October 15, 2026 looked at Alaska’s record 2024 whooping cough (pertussis) outbreak and found that children aged 6 months to 6 years who had completed the 3-dose DTaP primary series were 96.2% less likely to get lab-confirmed pertussis, and partly vaccinated children were 85.3% less likely. Unvaccinated children had about 26 times the odds of pertussis compared with fully vaccinated ones. The study is small (84 cases, 229 comparison children) and can’t tell us about severity, but it is a real-world check that the shots work. The schedule it tested is 2, 4 and 6 months, plus boosters at 15–18 months and 4–6 years.

What the study actually found

The report, published in the CDC’s Morbidity and Mortality Weekly Report (MMWR) by Alaska state epidemiologists, looked at what happened when pertussis surged in Alaska. Statewide incidence was unusually low in 2022 (0.27 cases per 100,000 people) and then hit a record 83 per 100,000 in 2024.

Between May and November 2024, Alaska recorded 113 lab-confirmed pertussis cases in children aged 6 months to 6 years. After exclusions, researchers compared 84 of those children with 229 matched children who had an acute cough but did not have confirmed pertussis, drawn from 17 health facilities.

The headline numbers:

• Fully vaccinated (3 or more valid DTaP doses at least 2 weeks before testing): adjusted vaccine effectiveness of 96.2% (95% confidence interval 89.6%–98.6%).
• Partly vaccinated (1 or 2 doses): 85.3% (95% CI 64.4%–94.0%).
• Unvaccinated: about 26 times the odds of pertussis compared with fully vaccinated children (adjusted odds ratio 26.1; the confidence interval is wide, 9.6–70.9).
• Among children with pertussis, 61.9% were unvaccinated, compared with 12.2% of the comparison children.

In plain terms: in this outbreak, most of the sick young children were the ones who hadn’t had their shots.

What this study can’t tell you

Honest caveats matter here, and the authors list several. The study did not have data on how sick the children got, so it can’t say how well DTaP prevents hospitalisation. The comparison group may have included a few children with untested pertussis. The sample was too small to compare 3 doses with 4 or 5 doses. And it covers lab-confirmed cases in children 6 months to 6 years, so it may not apply to older kids or very mild illness.

It also did not look at whether the mother had a pertussis shot (Tdap) in pregnancy, which can protect the youngest babies. The authors note that this passed-on protection fades by about 8 months.

The “protection fades” detail

Among fully vaccinated children, those who caught pertussis had gone a bit longer since their last dose than those who didn’t (median 15.3 months vs 10.2 months). That difference was not statistically significant, so treat it as a hint, not a finding. It fits earlier research showing acellular pertussis protection wanes over time, and the authors suggest that children who hadn’t yet had the 15–18 month or 4–6 year boosters may have been more vulnerable.

That’s the practical reason the boosters exist, not just the first three shots.

The DTaP schedule this study tested

The study measured effectiveness against the Advisory Committee on Immunization Practices (ACIP) schedule:

Doses given too close together don’t count as valid in the study, so keeping to the recommended intervals matters. Your paediatrician can tell you where your child is and what to do if a dose was missed or delayed. Note that “fully vaccinated” in the study meant 3 valid doses, which is the primary series, not the complete five-dose schedule.

Why this matters for babies under 1

The researchers point out that unvaccinated children with pertussis are more likely to become severely ill or need hospital care than vaccinated ones. Babies are too young to have the full series, which is why the first dose at 2 months and keeping appointments on time are the main levers a parent controls.

For the other side of the story (how many cases are happening nationally this year, kindergarten exemption rates, and how Tdap in pregnancy fits in), see our guide on whooping cough in 2026 and record vaccine exemptions. If you’re planning autumn appointments in one trip, our RSV shot timing guide and flu vaccine guide cover the other two.

Practical steps this week

1. Check your child’s record. Ask your paediatrician’s office or your state immunisation registry for a current vaccine record and compare it to the table above.
2. Put the next dose in your calendar the day you leave an appointment, not when you remember.
3. Call early about a worrying cough. If your baby has a cough that worries you, or has been around someone with pertussis, call your doctor promptly rather than waiting.
4. Keep everything in one place. Keep the vaccine record with your baby’s other health notes. Our New Parent Starter Bundle includes a “When to Call the Doctor” printable and a 0–12 month milestones checklist to keep alongside it.

The bottom line

This is one study in one state, with real limits, but it adds hard real-world evidence to a simple message: in a year when whooping cough hit record levels in Alaska, the children who had completed the DTaP series were overwhelmingly the ones who stayed well. Start at 2 months, keep to the schedule, and don’t skip the 15–18 month and 4–6 year boosters. Talk to your child’s paediatrician about any gaps.

Sources

• CDC MMWR — Effectiveness of DTaP Vaccine in Children Aged 6 Months–6 Years During a Statewide Pertussis Outbreak, Alaska, May–November 2024 (published October 15, 2026)
• Contemporary Pediatrics — DTaP 96% effective against pertussis in Alaska outbreak (October 15, 2026)