March 31, 2022
TOKYO – A third dose of novel coronavirus vaccine is estimated to provide about 70% efficacy in preventing the onset of COVID-19, according to a team of researchers from Nagasaki University and other institutions.
The findings are similar to those reported in overseas studies, and the team believes that a certain level of effectiveness can also be expected from the third round of vaccinations in Japan.
The Japan researchers examined data regarding 2,000 patients aged 16-64 who visited medical institutions for fever and other symptoms in 10 prefectures nationwide between January and February. They examined the relationship between their vaccination history and COVID-19 test results.
Among patients who had received a third dose of the vaccine from Pfizer Inc. or Moderna Inc. of the United States, the efficacy in preventing the onset of the disease was 68.7%. For individuals who had received just two doses, effectiveness was estimated at 42.8%, much lower than the 88.7% marked in the same analysis conducted from July to September last year.
The researchers believe the January-February period they analyzed fell during the time when the highly infectious omicron variant was rampant, which affected the vaccine’s effectiveness.
“A third dose of vaccine is thought to significantly increase effectiveness against the omicron strain, and it is important for Japan to accumulate data,” said Tetsuo Nakayama, a specially appointed professor of clinical virology at Kitasato University.