In 1946 veterinary researchers at Purdue University reported that something invading the guts of young pigs was causing diarrhea, vomiting and weight loss, ultimately killing most of them. The culprit was a coronavirus we know as transmissible gastroenteritis virus (TGEV).
TGEV has never harmed a human, and its relationship to SARS-CoV-2, the driver of COVID-19, is distant.”
TGEV took a strange turn in the 1970s. The disease it caused basically vanished when a TGEV variant that was even more transmissible, but less harmful, essentially immunized pigs against the original virus.
Source: Science, February 4, 2022. Link. If this saga of three little pig viruses has a moral that applies to humans, Omicron or later, even milder variants could help curb the COVID-19 pandemic, for now. But they might not protect us from the next big, bad coronavirus to find a way to our door.