A handful of children have been hospitalized for a potentially deadly bacterial infection, alarming some doctors about the possible return of a once-feared contagious disease that vaccines tamed.

Serious cases of Haemophilus influenzae type B, or Hib, once impacted 20,000 children in the United States each year. The disease spreads through coughing or sneezing with respiratory droplets containing bacteria.

Invasive infection included infants and toddlers developing pneumonia, meningitis, septic arthritis, blood infection and swelling in the throat, causing permanent disabilities and death in about 5% of cases, or around 1,000 children annually.

Older doctors have haunting memories of severe illness they saw — of brain swelling and children suffocating.

The Hib vaccine − introduced more than three decades ago and now recommended for all children younger than 5 − drastically cut cases, preventing nearly all vaccinated children from developing disease. Infants receive three or four vaccine doses beginning at 2 months old. The U.S. Centers for Disease Control and Prevention today reports fewer than 50 cases per year, a reduction of more than 99%.

But as more parents skip routine vaccinations of their children, doctors worry Hib cases will return in force. Two severe cases in a Florida beach town’s hospital in 2025, and another two cases presented at a Tennessee research institution, are sparking concern.

“If this was something adults would get, you would see a lot of people panicking,” said Dr. Eehab Kenawy, a pediatrician in Panama City, Florida, a tourist destination where the local hospital saw two severe cases in intensive care within a six-month period in 2025.

One was an unvaccinated 4-month-old who died, he said. Another was a 2-year-old (also not vaccinated), who had brain abscesses and seizures and has had lasting effects. Kenawy, who didn’t personally treat the cases but was on call at the time, first alerted a state Department of Health rule-making conference of the cases in December.

Both children were visiting from out of state, making it difficult to know how prevalent Hib was in the area. Health experts worry about undetected spread, especially amid cuts to CDC surveillance and reporting to detect diseases including Hib.

“What’s really going on?” said Dr. Paul Offit, director of the Children’s Hospital of Philadelphia’s Vaccine Education Center, who wrote a blog post titled, “The Return of Hib?,” in March. “This is not a disease you want to come back.”

CDC is not seeing an increase in preventable invasive Hib infections among children, Andrew Nixon, a spokesperson for the U.S. Department of Health and Human Services, said in an email. As of March 28, latest CDC surveillance data showed eight cases this year.

Dozens of states have expansive vaccine exemptions for religion and personal belief. Florida is looking to end school-entry vaccinations, including for Hib. Drops in vaccinations have already contributed to the rapid resurgence of measles outbreaks across the country.

“If we choose not to vaccinate, there are a number of serious diseases that children can acquire,” said Dr. Kathryn Edwards, a vaccine safety expert and pediatrics professor emerita at Vanderbilt University Medical Center, in Tennessee, where doctors recently saw two cases of Hib. “Parents need to know that, and doctors need to remember.”

Since the Hib vaccine nearly eliminated the disease, physicians today may not look for signs of infection in a child.

“We brought it down to pretty much zero in the country,” said Dr. Mathuram Santosham, professor of pediatrics and international health at Johns Hopkins University Bloomberg School of Public Health. Santosham, like Edwards, worked to pioneer the first Hib vaccines in the 1980s. “It’s frightening, not only for Hib, but for other diseases,” Santosham said.

Edwards, Santosham and Offit, now three leading experts on pediatric infectious diseases and vaccines, vividly recalled children with complications from Hib that they treated as young doctors, before vaccines were available.

In Chicago, Edwards witnessed a girl die from epiglottitis, swelling in the tiny cartilage covering the windpipe that closed her airway. In Baltimore, Santosham remembered the milky spinal fluid hitting his chest during a spinal tap, when he tried to test a 9-month-old with seizures and a bulging soft spot on his head; the child, who had severe meningitis, wound up in a vegetative state before dying, he said. In Pittsburgh, Offit remembered the aquarium in the children’s hospital’s small, dark room, used specifically to keep infected children calm to prevent them from spasming and closing their airways before they could get intubated.

“It’s just crazy that we’re going backwards on these vaccine-preventable diseases,” said Dr. Phillip Huang, director of the Dallas County Health and Human Services, in Texas.

Huang, who saw cases in medical school just before vaccines became available, said his county has continued to see significant declines of Hib immunization. Huang, past chair of the Big Cities Health Coalition, said federal monitoring has lagged in reporting and laboratory support to monitor Hib, making it harder to detect cases until it’s too late.

In Florida, Kenawy, a doctor for 27 years, has never seen the bacterial infection. But he now has to consider that a fever, which is common among children, might be a symptom of something much worse.

“I now have to think of these differentials,” he said.

Eduardo Cuevas is based in New York City. Reach him by email at emcuevas1@usatoday.com or on Signal at emcuevas.01.

This article originally appeared on USA TODAY: New Hib cases spark concern that deadly disease may return