Just 36% of people under age 65 who received two shots of a COVID-19 vaccine in Japan were protected against infection, yet the rate jumped to nearly 70% for those who got a booster shot, according to a new study from Nagasaki University.

The study, presented on Wednesday to the health ministry advisory panel on coronavirus measures, underscores the importance of getting a third jab, panel chair Takaji Wakita told reporters.

“We know that the coronavirus vaccine is more effective after three doses amid the spread of the omicron variant of the coronavirus,” Wakita, also director of the National Institute of Infectious Diseases, was reported as saying by Jiji Press. “We need to keep recommending that people get the third dose.”

The findings come on the heels of an announcement by U.S. biotech giant Moderna that a new vaccine under development that targets the omicron variant — the current dominant strain across the world — has shown promising results.

The "bivalent" vaccine, intended to stimulate an immune response against both the original strain and the omicron variant, succeeded in producing 1.75 times more omicron-specific neutralizing antibodies one month after the shot, the company said, noting that the vaccine will be a “lead candidate” for a fall 2022 booster drive in the U.S.

The vaccines currently available in Japan and elsewhere are based on the original strain of the virus and have failed to stem breakthrough infections. The Japanese government still recommends getting booster shots, mainly to prevent people from developing severe symptoms.

In the Nagasaki University study, researchers examined data from 5,169 people with COVID-like symptoms who visited 13 hospitals in 10 prefectures between January and March, when the omicron variant raged across the country. Of these patients, 41% tested positive for the coronavirus while the rest tested negative.

The researchers used the patients' vaccination records to estimate that a two-shot vaccine regimen helped prevent infections in 36% of people age 16 to 64 and 23.3% for people age 65 and older. Among those who received three shots — two vaccines and a booster — the vaccine effectively prevented infections in 68.7% of people age 16 to 64 and as high as 80.5% for those 65 and older.

As of Thursday, approximately 60% of Japan’s population have received three shots of a COVID-19 vaccine. The rollout of fourth shots, which began in late May, is so far limited to people over 60, as well as those with underlying health conditions who received their third dose at least five months ago.

Also reported at Wednesday’s meeting was news that Japan’s seven-day average of daily new infections has fallen through Tuesday across nearly all of the nation's 47 prefectures, with only Tokushima reporting an increase in cases.