Adverse events following COVID-19 virus vaccination in Japanese young population: The first cross-sectional study conducted by a questionnaire survey after the first-time-injection Marie Suehiro, Shinya Okubo, Kensuke Nakajima, Kosuke Kanda, Masanobu Hayakawa, Shigeru Oiso, Tsutomu Kabashima, Hideaki Fujita, Yukio Ando, Takahiro Muro