The wild cards are four Omicron subvariants.
Not long ago, people who recovered from COVID-19 felt confident that natural immunity would protect them from another case for at least six months, if not more. Vaccinated individuals, and especially those who’d received one or two booster shots, were equally sure that if they came down with the virus, the effects would be extremely mild (maybe some sniffles or headaches, maybe not), and afterward, they’d benefit from an extended stretch of natural immunity, too.…