Asthma in children may worsen after an infection with the coronavirus, doctors warn.

They studied nearly 62,000 U.S. children with asthma who had PCR tests for the virus in the first year of the pandemic, including more than 7,700 who tested positive. Infected children had significantly more asthma visits, hospitalizations, emergency inhaler use, and steroid treatments during the six months after their illness compared to children who tested negative and to their own prior history, researchers reported in the Journal of Allergy and Clinical Immunology: In Practice. Children who tested negative for the virus "had improved asthma control for the next six months, meaning fewer emergency department visits and hospitalizations for asthma, and less asthma treatment," said Dr. Christine Chou of Children's Health of Orange County, in California.

Results of earlier studies showing improvement in asthma control in the early part of the pandemic were likely due to public health measures like staying home and masking, which curbed exposure to asthma triggers, she said. Despite the overall impression that children with asthma did well during the first year of the pandemic, Chou added, the new study shows "longer lasting harm of COVID on children's asthma control."

Booster after infection adds little extra benefit vs omicron

Among people who were previously infected with the coronavirus, a third dose of an mRNA vaccine from Pfizer /BioNTech or Moderna may not boost their protection against the omicron variant of the virus, according to new data.

Researchers studied nearly 130,000 people tested for COVID in Connecticut from November 2021 through January 2022, including 10,676 with omicron infections. Roughly 6% to 8% had been infected with previous versions of the coronavirus, according to a report posted on medRxiv ahead of peer review. Two doses of an mRNA vaccine did help protect against omicron among people with prior infections, but "we did not detect an additional benefit of receiving a third booster dose among this population," said Margaret Lind of Yale University.

A separate study from Canada, also posted on medRxiv ahead of peer review, similarly found that more than two vaccine doses "may be of marginal incremental value" for protecting previously-infected individuals against omicron. The message, Lind said, "should be that (1) people should get two doses of mRNA vaccine regardless of if they have had a prior infection or not, that (2) people without prior infections should get a booster dose and that (3) people with prior infections should consider a booster dose, especially if they are in a high risk group for life threatening complications, but recognize that it may not provide significant additional protection against infection above two doses."