TOKYO, Dec 16 (Reuters) - Japan on Thursday officially approved Moderna Inc"s (MRNA.O) COVID-19 vaccine for its booster shot programme that began this month. The move followed a recommendation from health ministry experts on Wednesday that Moderna"s mRNA shot, used mostly at workplace inoculation sites to date, could be used as a third booster shot for those aged 18 or older. That"s the same standard that was applied to the shot developed by Pfizer Inc (PFE.N) and BioNTech (22UAy.DE), which has been given out about 71,000 times as a booster so far, or just 0.1% of the population After a relatively late start, Japan has fully inoculated almost 80% of its population, the highest among Group of Seven economies. The country has about 31 million doses left between the Pfizer and Moderna shots, with deals in place to get 170 million more in 2022. New coronavirus infections in Japan have slowed dramatically since a fifth wave that peaked in August. Experts say the fact that Japan started its vaccine push later may be helping keep COVID-19 cases low, as immunity from the shots for most people has not yet waned. read more Health minister Shigeyuki Goto said last week that boosters should be given as soon as possible, instead of holding firm to an eight-month lag from the first two shots.