Data from two areas in Japan show that during the country's fifth wave of coronavirus infections, nearly 10 percent of unvaccinated patients in their 40s and nearly 20 percent of those in their 50s developed symptoms that required supplementary oxygen.
Professor Wada Koji of the International University of Health and Welfare presented the results of an analysis of symptoms of COVID-19 patients at a meeting of the health ministry's expert panel on Wednesday.
The analysis was based on data from Sapporo City and Hiroshima Prefecture during the fifth wave of infections from July through September this year.
The study looked at more than 10,000 people who were infected in Sapporo. The ratio of patients who developed symptoms requiring oxygen was 9.8 percent among those in their 40s, and 18.0 percent for those in their 50s. The figure was 21.2 percent among those in their 60s, and 32.6 percent for those in their 70s.
The ratios were significantly lower for people who had received a vaccination more than two weeks before becoming infected and those who had been given two jabs. The figure was 0.1 percent among vaccinated people in their 40s, 0.3 percent among those in their 50s, 1.1 percent among those in their 60s, and 5 percent among those in their 70s. The data from Hiroshima showed a similar trend.
Wada says a very high percentage of middle-aged and elderly people develop symptoms that require oxygen. He says not being vaccinated can be said to be a risk factor in developing such serious symptoms.
He urged people to get vaccinated by the end of this month, saying that as temperatures drop, a resurgence of infections could occur.