参照元URL ： https://www.mhlw.go.jp/haishin/u/l?p=F-0dcZenoRtxYk2FY
COVID-19 Vaccine Booster Shots (3rd Dose)
WHO
Booster shots are available for all people who fulfill all of the following conditions
■ People who have had 2nd dose of their primary COVID-19 vaccination series at least 8 months ago, in principle. (*1)
■ People aged 18 years and older
■ People who have completed their primary vaccination (2 doses) under the Japanese Vaccination Law or vaccination equivalent to the primary series (*2) in Japan.
(*1) The Japanese government decided to shorten the interval of vaccinations in order to take all possible measures against COVID-19 infection. Healthcare workers and nursing home residents who are at high risk of severe illness will now be able to receive booster shots 6 months after the date of the 2nd dose, and from February 2022, other elderly people will be able to receive booster shots 7 months after the date of the 2nd dose.
(*2) People who meet the following conditions.
However, this is limited to those who have received two doses of any of the vaccines approved in Japan (Pfizer, Takeda/Moderna, or AstraZeneca).
(a) Vaccinated outside Japan.
(b) Vaccinated by the COVID-19 Vaccination Program for Japanese Residents Overseas.
(c) Vaccinated by the U.S. military employees in Japan.
(d) Vaccinated in clinical trials conducted by pharmaceutical manufacturers.
HOW
You will receive a "Vaccination Voucher" for the booster shot and a "Notification of Booster Shot for COVID-19 Vaccine (3rd dose)" from your municipality when it is your turn. Reservations can be made by phone or 
online.
(*1) The schedule for sending out vaccination vouchers and the start of reservation acceptance may differ by municipality.
(*2) If you do not receive your voucher after 8 months from the date you completed your primary vaccination, please contact your municipality.
WHEN
The period is scheduled from December 1st, 2021 to September 30th, 2022.
Vaccine Types
The mRNA vaccine is used regardless of the type of vaccine given for your primary vaccination. Currently, only the Pfizer’s vaccine has received pharmaceutical approval as a COVID-19 booster dose in Japan (The Takeda/Moderna"s vaccine is under review for approval).
Sample of notification from municipalities
Q&A