Whooping cough outbreaks in Europe, Asia and parts of the U.S. should be a reminder to get vaccinated, experts say.
Since January, cases of whooping cough have risen sharply in the U.K. and Europe, the largest surge since 2012.
China logged more than 15,000 cases in January of this year, a 15-fold increase over the same time period last year. This month there have been small clusters of reported cases among high school students in the San Francisco Bay Area and several isolated cases in Hawaii. From October through earlier this year, New York City went through an outbreak, with more than 200 cases of mostly young children.
What’s happening?
Whooping cough, or Bordetella pertussis — the bacteria that causes the illness — is a very contagious respiratory illness spread through small respiratory droplets. Due to widespread vaccination, whooping cough is largely under control in the U.S., but breakthrough cases, which are usually mild, do happen in people who are vaccinated.
“Some U.S. health departments have informed us of local outbreaks, which we expect to see every year,” Jasmine Reed, a Centers for Disease Control and Prevention spokesperson, told NBC News. “So we are not seeing anything unusual.”
Cases of whooping cough in the U.S. in 2024 are still lower than normal pre-pandemic levels. The U.S. usually logs around 20,000 cases of whooping cough every year. There were nearly 50,000 cases during a 2012 outbreak, CDC data shows.
Annual cases dropped steeply during the first two years of the pandemic, to 6,100 in 2020 and just 2,100 in 2021. Masking and physical distancing disrupted the normal cycles of many respiratory illnesses, including common colds, RSV and flu.
“Where the pandemic may have interrupted the normal cycle of pertussis is people were not getting vaccinated on schedule because families weren’t seeing their physicians as frequently as we would like,” said Dr. Thomas Murray, a professor of pediatric infectious disease at the Yale School of Medicine.
Warning signs for babies
Whooping cough causes cough seizures, a series of coughs that make it hard for a person to take a breath.
“When it finally stops, you take a breath in and it sounds like a ‘whoop,’” said Dr. William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine.
In adults and kids, whooping cough can look very much like a cold, prompting a runny nose and cough. But in young babies, an infection can be much more serious.
Pertussis inflames young babies’ bronchial tubes, or airways, making it difficult to breathe. The most common complication of an infection is pneumonia, which can be fatal. According to the CDC, there were 307 reported deaths from pertussis from 2000 to 2017. Nearly 85% were infants younger than 2 months.
“The disease is typically called whooping cough, but the very young babies don’t necessarily cough, they stop breathing,” Murray said, adding that the first thing parents should be aware of is anyone who is sick trying to come visit their newborn. “For babies themselves, any fever over 100.4 degrees is something their pediatrician needs to know about.”
If a baby’s lips are turning blue or they appear not to be breathing how they normally would, that “is something to be worried about, especially if they have been around someone who is sick,” Murray said.
The CDC recommends babies start their DTaP vaccine series — which can prevent diphtheria, tetanus and pertussis — starting at 2 months old. The series includes four more shots, at 4 and 6 months, 15 to 18 months, and 4 to 6 years old.
“The concern is that during the Covid period, a lot of kids were withheld from regular vaccination,” Schaffner said. “Now practitioners are trying to catch up.”
DTaP, which is formulated to elicit an immune response in babies, who have a less-developed immune system than kids, is about 98% effective at preventing pertussis in the first year following a five-dose series, according to the CDC.
Teens and adults may need a booster
The Tdap vaccine is recommended for kids age 11 and older who have not had a DTaP series, or adults who may need a booster.
“It’s important for all adults to have received a dose of Tdap. Following that, they should get either a Td or Tdap vaccine every 10 years,” Reed, of the CDC, said, noting that vaccination wanes over time.
Adult vaccination protects kids from whooping cough, and lessens the disease if the vaccinated person does get sick. However, “our compliance with that is less than optimal, which provides an opportunity for older people to get whooping cough,” Schaffner said.
While whooping cough can be dangerous for older adults, the primary concern is an adult passing the bacteria to an unvaccinated newborn baby.
“Anyone who comes to see the new baby should have had a recent inoculation with Tdap vaccine, to provide a cocoon of protection around that baby,” Schaffner said.
The CDC advises women to get a booster with every pregnancy. The American College of Obstetricians and Gynecologists recommends pregnant mothers get vaccinated with Tdap during their third trimester, which the CDC says prevents around 78% of pertussis cases and 90% of pertussis hospitalizations in babies younger than 2 months.
Is the virus mutating?
In 2019, researchers at the CDC found the bacteria that causes pertussis — bacterium Bordetella pertussis — has changed over time, which could make the current vaccines less protective than they once were.
“It’s not clear what effect, if any, those changes have on vaccine effectiveness,” Reed said.
Schaffner said the vaccines do still offer significant protection and are currently the best method for protection.
“It’s not like the flu. It mutates very slowly and these strains are sufficiently related to each other, so the vaccine still works,” he said.
The influenza virus mutates rapidly, as does coronavirus, which is why vaccines for those illnesses need to be updated every year. DTaP and Tdap vaccines are not reformulated.
The current outbreaks aren’t cause for alarm, but parents of new babies should be aware of the best ways to protect their newborns.
“It won’t turn into a pandemic because we have a highly vaccinated population,” Schaffner said. “However, let’s make sure that pregnant people get vaccinated, that babies are vaccinated on schedule, and the rest of us take the Tdap vaccine every 10 years.”
