There were more than more than 32,000 cases of whooping cough in 2024, the highest tally in a decade. In California alone, the disease struck 2,000 people between January and October last year.

More than 60 infants younger than 4 months were hospitalized in the state. One died.

Whooping cough, or pertussis, is just the most stark example of what happens when vaccination rates decline. But it is far from the only one.

The pandemic interrupted childhood immunizations across the country, and rates have not yet recovered. As a result, hundreds of thousands of children are increasingly vulnerable to diseases once largely relegated to history books.

Most of them predominantly affect young children, like measles, mumps and rubella. But if immunizations continue to fall over the next few years — because of rising distrust, or more restrictive federal policies — preventable infectious diseases will resurface in all age groups, experts say.

“It might take a year or two, but there’s no question,” said Pejman Rohani, an infectious disease epidemiologist at the University of Georgia.

“We will have outbreaks,” he said.

It’s not just the unvaccinated who will have to worry. Even adults who were vaccinated decades ago may find themselves vulnerable to what are now considered childhood diseases.