Japan allows mixing COVID-19 vaccine doses for booster shots

The Yomiuri Shimbun

November 16, 2021

COVID-19 vaccine booster shots can be from a different manufacturer than the first two doses, the health ministry decided Monday.

The government in principle requests the same manufacturer’s vaccine to be administered, but it decided to allow mixing certain manufacturers after examining the efficacy and safety of such use. The strategy is part of the Health, Labor and Welfare Ministry’s basic policy for booster shots.

According to the basic policy, the booster shots will be administered from Dec. 1 through September 2022 and will be available to everyone 18 and over who wishes to receive them. The health ministry’s expert panel agreed Monday to publicly fund the entire cost of conducting booster shots.

Generally, a third dose should be given after at least eight months from the second dose. However, the ministry decided it can be administered after six months if municipal governments feel the need based on such factors as the coronavirus infection situation, as some data suggests that vaccine efficacy is reduced by half after about six months from the second dose.

Following moves by Western countries, Japan will use vaccines using messenger RNA for booster shots. Based on overseas clinical trials, the government determined that there was no problem to alternatively use vaccines made by different manufacturers in terms of efficacy and adverse reactions.

Domestically, vaccine manufactured by U.S. pharmaceutical giant Pfizer Inc. has received special approval for booster shots, while vaccine manufactured by U.S. biotech firm Moderna, Inc. is currently under review.

Booster shots will be recommended to all eligible residents, with special emphasis on medical workers and people with higher risk of developing serious conditions, such as people with underlying diseases and the elderly. Booster shots for people 12 to 17 will be considered as soon as data is collected.

Japan’s COVID-19 vaccination rollout started in February with medical workers given the Pfizer vaccine. In general, second doses were given to medical workers from March, people 65 and over from May and people under 65 from July. The vaccination rate for the second dose exceeds 75% in the nation.

Delivery of the Pfizer vaccine for booster shots started Monday. Enough vaccine for about 4.1 million doses, which are expected to be administered from December through January, will be distributed across the nation by the end of November.