Japan's health ministry has urged local governments to prepare for the administration of COVID-19 vaccine to children aged 5 to 11, expanding inoculations to this age group in February at the earliest, its officials said Wednesday.

While the Ministry of Health, Labor and Welfare has sent the notice dated Tuesday to municipalities, some health experts have expressed concern amid uncertainty over the efficacy and safety of the vaccine in children aged under 12.

U.S. pharmaceutical giant Pfizer Inc. and German partner BioNTech SE applied last week for Japanese government approval to inoculate children in the age group with the vaccine they jointly developed.

Pfizer's vaccine is currently available free of charge only to people aged 12 and older in Japan.

In the United States, vaccinations of children aged 5 to 11 have begun, following approval by the Centers for Disease Control and Prevention.

Data from clinical trials conducted by Pfizer in the United States and other countries show that administration of a third adult dose of the vaccine was 90.7 percent effective in preventing COVID-19 infections in children aged 5 to 11.

The trials also showed that while the subjects experienced sore arms, fatigue and headaches the next day, the side effects disappeared quickly and there were no safety issues.

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