Chabad.org — English translation + Rashi
Torah Temimah (Pesachim 66b): “איש איש כי יהיה טמא” — an individual is deferred to Pesach Sheni; the community is not deferred but offers in tumah.
English: Rabbi Yochanan said: as the verse states “A man, a man who becomes tamei by a nefesh.” An individual is deferred to Pesach Sheni, but the community is not deferred to Pesach Sheni; rather they offer in tumah.
Distinction individual / community — the doubled “ish ish” marks the private case that is pushed to the second month.
Communal obligation is strong enough that tumah does not cancel the offering; private tumah does.