In-Depth: Omicron is causing more cases of croup in kids under 5

Baby cough
Posted at 8:30 PM, Feb 02, 2022
and last updated 2022-02-02 23:56:26-05

SAN DIEGO (KGTV) – Doctors at Rady Children’s Hospital say they’re seeing a new symptom in children under five infected with the omicron variant of COVID-19: croup.

Croup is an infection of the upper airways that produces a distinctive barking cough. Other viruses like influenza can cause croup, but the illness was rarely seen with COVID-19 until the emergence of omicron.

Croup has become a “signature symptom” of the variant, said Dr. John Bradley, director of infectious diseases at Rady Children’s Hospital.

Children under five are most susceptible because they have the smallest airways. “If you have a child with a small airway who gets any swelling of the mucous membranes of the airway, then it’s difficult to get air down into the lungs,” Dr. Bradley said.

If untreated, croup can cause serious illness.

A new study funded by the National Institutes of Health found that cases of croup at children’s hospitals nearly tripled in December when omicron took off.

Overall, serious illness in children remains rare, but the study found 31.6 percent of the kids with croup from COVID developed severe disease, more than twice the rate of children without croup.

Throughout the pandemic, the hospitalization rate for children has been well below the rate of adults, but two weeks ago, the rate for kids four and under nearly matched the rate of adults aged 18 to 49 for the first time. Both cohorts saw a hospitalization rate of 7 cases per 100,000 individuals.

That’s why doctors are so eager to get a vaccine for this youngest age group, but finding the right dose has been a challenge. Pfizer has been testing a vaccine that is one-tenth the dose given to adults.

In December, Pfizer announced this low-dose formula for its vaccines performed well in children six months to 2 years old, but the antibody levels were not as robust in children 2 to 4.

Pfizer announced it would begin trials on a third dose in these children, and some experts predicted the company would need to restart its trial. However, the FDA encouraged the company to apply for emergency authorization anyway.

“The two doses didn’t get as high a protection as they wanted, but it got you partway there,” said Bradley.

In press releases, Pfizer has expressed confidence that three doses will produce an equally strong response in these young kids and says there have been no concerning side effects. Advisers to the FDA will spend hours publicly examining Pfizer’s data Feb. 15.

By allowing Pfizer to seek authorization now, parents could begin a two-dose vaccine series as early as March. Pfizer is expected to have data on the third dose around the time most families would be due for that shot, Bradley said.

“We’re getting vaccine into kids two to three months earlier with this method, with no problems with safety,” he said.

For Bradley, there’s added urgency to vaccinate this young age group. He said Rady Children’s Hospital is just beginning to see the first cases of MIS-C caused by omicron. The rare inflammatory syndrome takes several weeks to develop and can be life-threatening.

Last month, the CDC found that Pfizer’s vaccine was 91 percent effective at preventing MIS-C in children 12 to 18.