Photo/Illutration Health care workers prepare to carry out vaccinations against COVID-19 in Osaka’s Chuo Ward on Feb. 19. (Jin Nishioka)

The nation's first cases of suspected side effects from vaccination against COVID-19 were reported after a patient developed hives, or itchy welts on the skin, and another complained of chills.

The individual who developed hives was inoculated at Toyama Rosai Hospital in Uozu, Toyama Prefecture, on Feb. 19, the prime minister’s office tweeted Feb. 20. The person's condition was said to have improved by the end of the day after receiving treatment.

Hives is known to be among side effects associated with inoculation against strains of influenza.

The health ministry said it is the nation’s first case of a suspected side effect from the coronavirus vaccination that the government became aware of.

If an individual develops only hives, the condition is not considered serious.

The health ministry said it had confirmed one other case of a suspected side effect from the novel coronavirus vaccination by 5 p.m. on Feb. 20.

In that instance, an individual developed chills after receiving a jab on Feb. 19, but recovered the following day.

Initially the hospital said it was anaphylaxis, a serious allergic reaction, but later amended the report.

Vaccination against the novel coronavirus began on Feb. 17 in Japan, with health care workers the first to receive their shots.