Japan will start discussing as early as next week whether to administer third shots of coronavirus vaccine, potentially by the end of the year, amid the spread of the highly contagious Delta variant, sources familiar with the matter said Friday.

Health experts on a government subcommittee on the coronavirus vaccine are expected to take up the matter as well as the possibility of combining doses of vaccines produced by different manufacturers. Three COVID-19 vaccines developed by Pfizer Inc., Moderna Inc. and AstraZeneca Plc are currently available in Japan, which are all administered in two doses.

The vaccine makers have said third shots would be necessary to increase protection, with a number of breakthrough cases in which fully vaccinated people have contracted COVID-19 reported in Japan and abroad. Taro Kono, the minister in charge of Japan's vaccination rollout, said late last month the health ministry is weighing cross vaccination to help ease supply concerns and accelerate the country's inoculation program.

Studies show that COVID-19 antibodies decrease six months after second shots have been administered and vaccine efficacy against the Delta variant becomes lower over time.

The discussions will take place after World Health Organization chief Tedros Adhanom Ghebreyesus said earlier this week that some wealthy countries should suspend their ongoing or planned administration of third shots until at least the end of the year to ensure vaccine supplies for developing countries.

Vaccinations in Japan have picked up pace in recent months, nearly catching up with the United States. As of Thursday, 61.9 percent of the Japanese population had received at least one dose of COVID-19 vaccine and 49.8 percent two doses.

The government is aiming to complete the full vaccination of all eligible people who wish to be inoculated by early November, and the administration of third shots would start sometime after that.

Some countries have already selected target populations for booster shots, such as 12-year-old or older in Israel, 18 or older in the United States, and elderly and immunocompromised people in France and Germany.

The government has signed contracts to receive an additional 50 million doses of Moderna's vaccine as well as 150 million doses from Novavax Inc. and is discussing an additional 120 million doses with Pfizer. The vaccine doses will be used if the government decides to administer booster shots.

==Kyodo

© Kyodo News International, Inc., source Newswire