Whooping cough cases are rising, and doctors are bracing for yet another tough year.

There have been 8,485 cases reported in 2025, according to preliminary data from the U.S. Centers for Disease Control and Prevention. That’s twice as many cases as this time last year, based on the CDC’s final tally.

Rates of whooping cough, or pertussis, soared last year, which experts said wasn’t unexpected. The number of cases fell during COVID-19 because of masking and social distancing. Plus, experts said, the illness peaks every two to five years.

But experts say the outbreaks of vaccine-preventable illnesses, like measles and whooping cough, could be indicative of changing attitudes toward vaccines. U.S. kindergarten vaccination rates fell last year, and the number of children with vaccine exemptions hit an all-time high.

“There’s unfortunately been increasing anti-vaccine sentiment in the United States,” said Dr. Ericka Hayes at the Children’s Hospital of Philadelphia. “Our recovery is not nearly as quick as we expected it to be and we needed it to be. And again, when you fall below 95% for vaccinations, you lose that herd immunity protection.”

Whooping cough tends to peak around this time of year and in the fall. It’s usually spread through respiratory droplets in the air, when people with pertussis cough, sneeze or breathe close to others. The symptoms are similar to a cold but the cough becomes increasingly severe with a distinctive sound — a “whoop” as the person tries to take in air. It is treated with antibiotics.

In the past six months, two babies in Louisiana and a 5-year-old in Washington state have died from whooping cough.

The pertussis vaccine, which also protects against diphtheria and tetanus, is given at two months, four months and six months. The CDC recommends adults get follow-up doses every 10 years.