You have pretty large hands... For young men, it is about 1/10000 with the Moderna vaccine. No fatal cases AFAIK, but considering that we are talking about young men who are less likely to get severe covid, it is less than ideal. Benefit/risk is still good, but will it still be the case if we need a new dose every 6 months?

Anyways, for that reason, health authorities recommend Pfizer/Biontech over Moderna for people under 30. And it is probably what encouraged the use of half doses of the Moderna vaccine for booster shots.