Men aged 12-29 can switch to Pfizer vaccine due to risk of heart inflammation linked to Moderna

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Men aged 12-29 can choose Pfizer

Rare cases of an inflamed heart muscle (myocarditis) or inflamed tissue surrounding the heart (pericarditis) have been reported in Japan and overseas among people who received the Moderna vaccine. The adverse reactions tend to be higher in males aged 12-29.

The situation has prompted Japan's health ministry to provide information that allows men in the target group to make an informed choice between the Pfizer or Moderna vaccine for their first or second shot. Men can switch to Pfizer for their second shot even if their first one was Moderna.

Until now, basically, Japan has not allowed people to receive different vaccines for their first and second shots.

Japan has rolled out three vaccines: Pfizer, Moderna and AstraZeneca. Clinics and municipalities mostly offer Pfizer, while Moderna has been used in corporate and university settings, and by municipalities. The AstraZeneca vaccine is also offered by municipalities, limited to people aged 40 and older.

Heart inflammation rates

As of November 12, Japan reported an inflammation rate of 60 cases per one million men aged 12-19 who received Moderna shots, and 40 in the 20-29 age bracket. Significantly fewer cases were reported with Pfizer.

Making an informed choice

Health officials debated whether they should recommend the Pfizer vaccine for all young men. But with some heart inflammation cases also linked to Pfizer, they decided to provide information that allows men in the target group to choose for themselves.

Chest pain or shortness of breath are the typical symptoms of myocarditis and pericarditis. They can develop within four days or so after the vaccination. If symptoms appear, people, especially young men, are urged to seek immediate medical attention.

How men can decide

The ministry has asked municipalities to contact all men in the target age group who have vaccination reservations for Moderna. Those who want to switch to Pfizer will be accommodated – including preferential reservation slots if needed.

An interval of more than 27 days is necessary for those who have already received a first dose of Moderna and opt for Pfizer for the second.

Men who already have reservations for Moderna vaccine through companies or universities – and want to switch – may need to make a booking through their local municipality instead.

This information is accurate as of November 24, 2021.