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Japan health ministry allows young men to choose Pfizer shots over lower inflammation risk

A poster indicating the deadlines for reserving coronavirus vaccinations is seen in Tokyo's Ota Ward on Oct. 12, 2021. (Mainichi/Ai Yokota)

TOKYO -- Japan's Ministry of Health, Labor and Welfare decided in an expert panel meeting on Oct. 15 that it will call on males aged 12 to 29 to get vaccinated with caution, on the grounds that rare cases of heart inflammation were higher after vaccination with Moderna Inc.'s coronavirus vaccines compared with Pfizer Inc.'s shots.

    As the country's COVID-19 vaccine rollout is in its final stage, measures for young individuals have been at the center of attention. Although the health ministry presented a proposal to recommend that males aged 12 to 29 take Pfizer vaccines, many members at the expert panel meeting were hesitant and the plan was shelved.

    Both Moderna and Pfizer are messenger ribonucleic acid (mRNA) vaccines, and in very rare cases, after receiving the vaccines, people develop myocarditis, or heart muscle inflammation, and pericarditis, or inflammation of the lining around the heart. Many such cases are seen in young men, and they tend to occur more after the second shot than the first.

    According to the health ministry, as of Oct. 3, myocarditis and pericarditis had occurred among boys aged 12 to 19 receiving Moderna vaccines at a rate of 28.83 per 1 million people, and at a rate of 25.65 per 1 million people for men in their 20s. In contrast, Pfizer vaccines had an occurrence rate of 3.69 among boys aged 12 to 19, as well as 9.62 for men in their 20s, which shows that Moderna shots have a clearly greater frequency of inflammation cases.

    Symptoms are mild for either vaccine, and most people who experience them have recovered. As the occurrence rate of heart muscle inflammation caused by coronavirus infection is higher than that occurring after vaccination, the expert panel had previously stated that it "cannot recognize a serious concern" as "the merits of getting vaccinated outweigh the risks."

    However, from September, the frequency of heart inflammation cases presented at expert panel meetings showed high occurrence rates among males aged 12 to 29 receiving Moderna shots, and as more people have been vaccinated, a widening gap of inflammation cases has been seen between Moderna and Pfizer vaccines. Furthermore, new moves have been taken as precautionary measures, including a temporary suspension of Moderna vaccine use for people aged 30 and under in Sweden, and people aged under 18 in Denmark.

    At the expert panel meeting, the health ministry made a suggestion to recommend taking Pfizer vaccines, as suspected cases of heart muscle inflammation frequently occurred after Moderna vaccine shots. However, a number of panel members voiced views such as "By using the word 'recommend,' this may give the impression that one is inferior to the other," as well as concerns over whether they could "go as far as to recommend Pfizer" while there were almost no past cases of vaccinations using different types of vaccines for the first and second doses. As a result, the health ministry has called off recommending Pfizer vaccines, and will continue to carefully monitor the situation in and outside Japan.

    Following discussion at the expert panel meeting, the health ministry will approve adding concerns surrounding heart muscle inflammation as a condition for mixing and matching different vaccines for the first and second shots. It will also issue warnings targeting males aged between 12 and 29 in pamphlets, the ministry's official website, and other places. The health ministry has called on individuals to get examined at medical institutions quickly if they develop symptoms including chest pain, palpitations, shortness of breath, and swelling, within around four days from vaccination.

    The health ministry also contacted each prefectural government on Oct. 15 and said that it will supply additional Pfizer vaccines which become necessary when young males opt for such vaccinations.

    (Japanese original by Sooryeon Kim, Lifestyle and Medical News Department)

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