TOKYO: People who contract COVID-19 after receiving two doses of the novel coronavirus vaccine have a far lower risk of becoming severely ill than unvaccinated patients, a major study by a Japanese medical institution showed Tuesday.

Among elderly people aged 65 or over, the percentage of fully vaccinated coronavirus patients, or so-called breakthrough infection cases, requiring treatment in an intensive care unit was approximately a seventh of the share of such unvaccinated people, according to the study by the National Center for Global Health and Medicine in Tokyo.

The percentage of deaths among fully vaccinated elderly patients was roughly a third of the death rate of unvaccinated people, the study showed.

The study covered 3,417 people who were admitted to hospitals across Japan in July or later and reported to the national center by Sept. 22. Of them, around 90 percent had not been vaccinated or received only one dose.

Of the 2,574 people who had clear records of the vaccination date, 54 people, or 2 percent, became infected with the coronavirus at least two weeks after the second dose, which is considered the time required for the vaccine to become fully effective.

Of them, 44 were elderly people and had a lower percentage of displaying symptoms such as a fever and cough than among unvaccinated people and people who had received  one shot.

Among them were two deaths–a woman in her 80s and a man in his 60s–but both suffered underlying health conditions such as heart failure and high blood pressure.

Looking at the treatment of elderly patients by vaccination history, 16.3 percent of unvaccinated patients required ICU treatment, compared with 2.3 percent of breakthrough patients.

The death rate came to 14.7 percent among the unvaccinated elderly, compared with 4.5 percent among breakthrough patients. The share of the fully vaccinated elderly requiring oxygen inhalation was roughly a half of that of such unvaccinated patients.

“The study shows, once again, that while COVID-19 vaccines tend to lower the risk of developing severe symptoms, there are a certain number of breakthrough infection cases,” said Nobuaki Matsunaga, a senior official of the national center.

“As many hospitalized patients have not been fully vaccinated, people need to take extra caution until they have completed their second dose,” Matsunaga said.

JIJI Press