TOKYO: Vaccines against the novel coronavirus are effective in preventing COVID-19 symptoms from becoming severe, a working team of the National Governors’ Association said in a survey report Sunday.

The survey focused on the COVID-19 situation in each of Japan’s 47 prefectures during the fifth wave of infections this summer and measures taken in the fight against the coronavirus.

The report said that infections during the fifth wave, in which the highly contagious delta variant was dominant, spread twice as fast as in the fourth wave. New positive cases increased explosively, putting the health and medical care systems in danger in many regions, it said.

The proportion of vaccinated people in new infection cases was very low, the report noted. In Niigata Prefecture, central Japan, no severe COVID-19 symptoms were confirmed for people who caught the virus after getting two vaccine shots, it said.

Prefectures including Okayama, western Japan, reported that requests for shorter operating hours led to decreases in the flows of people and new positive cases, as well as the number of infection clusters at eating and drinking establishments.

But Nara Prefecture, western Japan, did not request restaurants and bars to shorten operating hours during the fifth wave, concluding that there are no clear gaps between the number of new infection cases when a request for shorter operating hours is in place and that when there is not such a request.