Until recently, 8 in 10 toddlers had received four doses of the DTaP vaccine by age 2, and case rates were controlled. But vaccine coverage has declined since the covid pandemic and increases in state nonmedical exemptions have widened immunity gaps, which is when the proportion of individuals who are immune falls below the level needed to contain spread.

Texas logged 1,928 pertussis cases in 2024. By October 2025, the state had exceeded 3,500. National numbers are just as stark: In the first three months of 2025, the U.S. tallied 6,600 cases — four times last year’s pace and 25 times 2023’s. Several states are posting their highest case totals in a decade, and outbreaks from Louisiana to South Dakota to Idaho make clear this surge isn’t regional. It’s everywhere.

Texas lawmakers recently passed a law that made it easier for parents to claim nonmedical exemptions from school vaccine requirements by allowing them to download exemption forms online. These forms now go straight to schools, not health departments, making the exemptions harder to track.

Dallas County Health and Human Services Director Phil Huang said the full impact of the new exemption rule is not yet known because it began this school year, but he expects it will make school-level vaccination rates fall even more.

He’s already noted a dramatic drop in vaccinations. Normally, during back-to-school season, “our whole front downstairs area is packed,” he said. “We did not see that this year.”

Huang believes fear of immigration enforcement may be keeping at least some families, especially Hispanic families, from getting vaccinated. Dallas County is about 40% Hispanic. “We think that a lot of them are deterred by the ICE activity,” he said, referring to Immigration and Customs Enforcement.

More complications: These vaccines protect against severe disease, but protection against infection fades over time, as is the case with the covid and influenza vaccines.

The U.S. switched in the 1990s from whole-cell pertussis vaccines to “acellular” ones, which cause fewer side effects but do not last as long. Because more adults today than in the past received the acellular vaccine as children, many have lost immunity over time and may unknowingly pass the infection to babies.

Whooping cough is especially dangerous for infants under a year old. Some stop breathing during coughing fits. Many need hospital care, about 1 in 5 of whom develop pneumonia, and about 1% of whom die.

Because of this high risk, the CDC urges pregnant women to get a Tdap vaccine during every pregnancy. This allows the mother’s antibodies to pass to the baby before birth.

Health officials once promoted “cocooning,” vaccinating all family members and caregivers around the baby, but that strategy was hard to carry out in real life and is no longer widely recommended. Vaccination of pregnant women and babies at 2 months of age remains the strongest protection.

Modern PCR testing is also uncovering more pertussis cases than in the past. Many clinics now routinely use this lab-based technology to test for several respiratory infections at once, including pertussis. Ten years ago, these panels were uncommon.

CDC experts say this explains part of the rise in case counts. But the large number of infant hospitalizations and the size of state outbreaks show that true transmission has also increased.

Doctors normally treat pertussis with macrolide antibiotics, such as erythromycin, azithromycin, and clarithromycin. These drugs work best early in the illness and help stop spread. Another drug, trimethoprim-sulfamethoxazole, is an option for some older infants and adults.

But macrolide-resistant pertussis has become common abroad, especially in China, and recent reports show resistance rising in Peru. In the U.S., resistant cases have been rare.

CDC officials warn that resistant strains could sp