<a href="https://www.nejm.org/doi/full/10.1056/NEJMc2302462" target="_blank" rel="noopener nofollow">https://www.nejm.org/doi/full/10.1056/NEJMc2302462</a><br><a href="https://www.mhlw.go.jp/content/001133311.pdf" target="_blank" rel="noopener nofollow">https://www.mhlw.go.jp/content/001133311.pdf</a><br><a href="https://www.pref.ehime.jp/h25500/kansen/covid19/documents/xbb_leaflet.pdf" target="_blank" rel="noopener nofollow">https://www.pref.ehime.jp/h25500/kansen/covid19/documents/xbb_leaflet.pdf</a>