Smallpox is extinct, except for small amounts locked in highly secure freezers at CDC in Atlanta and the Russian equivalent of CDC in Moscow. As bad reactions to the smallpox vaccine can be severe, it is NOT A GOOD IDEA to use it, except where there is an actual risk of being infected.
https://en.wikipedia.org/wiki/Smallpox Why, just as with installing antimalware on Macs, being inoculated for smallpox currently causes more problems than its worth. Those who work in labs where they might be exposed should be inoculated against smallpox; those who work with Mac malware should install antimalware. The vast majority of the world's population is at limited risk of being infected by smallpox and should not be vaccinated against it as there are likely severe complications. It used to be that smallpox vaccinations were necessary; virgin field fatalities for major smallpox epidemics were often over 70%, and in at least one case exceeded 90%. Smallpox was very dangerous indeed, but now it's dead. The vast majority of Mac users should not install antimalware as there are likely severe complications. It used to be that there was a significant malware threat to Macs; the Autostart Worm went around the world in under two weeks from go. The threat level is much lower now. (Please note: while it is true that not getting smallpox vaccine is probably a good thing, not getting measles, mumps, influenza, or other major vaccines is a very bad thing. Smallpox is extinct. Measles etc are NOT. Measles, mumps, and smallpox conquered the western hemisphere for the white man. See further Jared Diamond's excellent book, _Guns, Germs, and Steel_, that would be were I got the numbers quoted above. Measles in particular is EXTREMELY DANGEROUS and those who don't vaccinate against it are asking for trouble.
https://en.wikipedia.org/wiki/Measles For those who don't take the flu seriously, it should be noted that the 1918 Spanish Flu epidemic killed more people than the First World War.
https://en.wikipedia.org/wiki/Spanish_flu Note that the flu is LESS DANGEROUS than measles; for one thing, it has a lower body count.)
If you feel that you must use Mac antimalware, go ahead. Just know that you're wasting your time, money, and resources unless you're one of those at risk for infection. Windows users should use antimalware, major infections abound there. Most infections, great and small, have been rendered extinct on Macs. Don't take my word for it, look up the CVEs posted for all platforms. Virtually all CVEs for Macs are trojans; if users merely don't click on them, trojans cannot affect anything. Almost all the others are adware, which gets blocked if users use an adblocker.