COVID-19 May Raise Risk of Asthma and Allergies, Study Finds

COVID-19 may carry longer-term consequences for the respiratory system beyond the initial infection, according to new research published in the Journal of Allergy and Clinical Immunology.

The study, drawing on health records from nearly 5.4 million people, found that those who contracted COVID faced significantly higher odds of developing certain airway diseases. Compared with people who had neither been infected nor vaccinated, patients with a history of COVID showed a 66% greater risk of asthma, a 74% increased risk of chronic sinus inflammation, and a 27% higher risk of hay fever.

“Our findings suggest that COVID-19 can trigger type-2 inflammation in the airways, which may explain the link to asthma and allergic conditions,” said Philip Curman, PhD, senior investigator and researcher in medical epidemiology and biostatistics at the Karolinska Institute in Sweden. Importantly, he added, vaccination seemed to provide meaningful protection against these complications.

To assess the impact of vaccination, the researchers compared health outcomes in people who were fully vaccinated against COVID with those who had never been infected. Vaccinated individuals had a 32% lower risk of asthma, suggesting that protection extended beyond preventing severe disease. When the comparison shifted to those who had been infected, the differences were even more pronounced: COVID patients were more than twice as likely to develop asthma or sinus problems and faced 40% higher odds of hay fever than their vaccinated counterparts.

Notably, COVID infection did not increase the risk for other immune-related conditions, such as eczema or esophageal inflammation, underscoring that the virus’ impact may be concentrated in the respiratory tract.

While the study is one of the largest to date on the topic, the authors caution that the results show an association rather than a direct cause-and-effect link. Still, the findings add to growing evidence that vaccination not only shields against acute infection but may also protect the body from lingering respiratory complications.