COVID-19 infection might increase a person’s risk of developing asthma, seasonal allergies and long-lasting sinus problems, a new study says.

However, vaccination appears to reduce this risk, researchers report in the Journal of Allergy and Clinical Immunology.

“It is interesting to see that vaccination not only protects against the infection itself, but also appears to provide good protection against certain respiratory complications,” senior investigator Philip Curman, a researcher in medical epidemiology and biostatistics at Karolinska Institute in Sweden, said in a news release.

For the study, researchers compared nearly 974,000 people who’d been infected with COVID with more than 4.4 million people who’d been neither infected nor vaccinated. The records came from a major U.S. electronic health database.

Results showed that COVID patients had a 66% increased risk of developing asthma.

They also had a 74% higher risk of chronic sinus inflammation and a 27% increased risk of hay fever, researchers said.

However, infection did not increase risk of other diseases like eczema or esophageal inflammation, researchers siad.

“Our results suggest that COVID-19 can trigger type-2 inflammation in the airways, but not in other organs,” Curman said.

The team also compared healthy people against those vaccinated against COVID and found the opposite effect — risk of asthma was 32% lower against those who’d gotten the jab.

But when COVID patients were compared to those vaccinated against COVID, an even clearer effect was found.

People infected with COVID had more than twice the risk of asthma or sinus problems and 40% higher odds of hay fever, compared to those who’d been vaccinated.

However, researchers warned that the study could only show an association, not a cause-and-effect relationship, between COVID and airway problems.