An FDA-approved vaccine for smallpox and mpox is effective but causes side effects. The other requires multiple doses. An experimental single-dose vaccine uses the horsepox virus to harness the ...

It all started with an unremarkable trip to grandma’s house in 1970. But two days into the visit, something went terribly wrong. The 9-month-old grandson fell ill. First, a fever. Then, a nasty rash.