Here’s how: Smallpox vaccine protects against monkeypox, so s’pox eradication -> end of mass vax -> dwindling m’pox immunity -> 20x more cases in Congo -> more chances to better adapt to humans. The big Q: Has this already happened? 7/ https://t.co/SvEntsKEd3

— Ed Yong (@edyong209) May 19, 2022