Studies showed that Covid-19 antibodies would decrease six months after taking the second shot of the vaccine and jab efficacy against the Delta variant would become lower over time.
In addition, vaccine makers said that since confirmed infections among fully inoculated people were increasing in Japan and abroad, the booster shot would be necessary, quoted the Ministry as saying on Friday.
Health experts of a Japanese government sub-committee agreed on the necessity of the third shot and approved the Ministry's plan to start inoculating people at least eight months after they received their second dose.
Based on Japan's vaccination progress, people may start receiving the booster shot from November, and the government will discuss the population eligible for the third shot and the order of priority based on data and the progress of other nations.
A sub-committee member said medical workers treating Covid-19 patients need to be allowed to receive their third shot as soon as possible, but another member thought people who have not received two shots should be prioritized.
The Ministry said that in principle, all three doses should be from the same manufacturer.
However, it said that under certain situations, people could take the booster shot produced by a different company, giving the first two shots should be doses of the same supplier, and it would revise rules to enable that.
Japan currently uses vaccines developed by Pfizer Inc., Moderna Inc., and AstraZeneca Plc.