NHK has learned the results of a study which show that people who had COVID-19 are more likely to suffer from aftereffects than those who had influenza.

Researchers led by Nagoya Institute of Technology Professor Hirata Akimasa said people who had COVID were much more likely to visit medical institutions complaining of aftereffects.

The researchers studied the medical expense receipts of 290,000 people who visited medical institutions from January through March 2019.

They focused on people who did not have serious underlying conditions, and compared those who had suffered from influenza with those who had not.

They say those who had the flu were 1.8 times more likely to visit medical institutions for coughs and headaches within two months of getting the virus. The likelihood of hospital visits for fatigue was about the same between the two groups.

The researchers also compared people who got COVID during Japan's sixth wave from around the start of 2022 with people who had not been infected.

They say those who had suffered from COVID were 8.2 times more likely to see doctors for coughs and 7.92 times more likely to see them for respiratory difficulties. The likelihood was 5.97 times higher for taste and smell disorders, 3.64 times more for fatigue and 2.87 times higher for headaches.

Hirata said many people were thought to have immunity during the sixth wave through infection or vaccination, but compared with those who had the flu, it appears that people who had COVID were much likelier to suffer from symptoms thought to be aftereffects.

He said the risks following a COVID infection should be carefully studied.