AHC: Vaccines either don't exist or are not as widespread as they are in OTL

What would need to happen to create a world where vaccines (as in vaccines for smallpox, polio, measles, etc) either don't exist or are not as widespread as they are in our timeline?
 
You would probably need a serious outbreak of religious obscurantism/fundamentalism in the late 1500s or early 1600s. A different outturn of the Spanish Armada or the Thirty Years War perhaps? Essentially you would enormously retard the speed of the industrial revolution and mortality rates would remain very high prior to the introduction of piped water, carbolic soap and disinfectants. Even with those it would remain significantly higher than OTL. OTOH autoimmune diseases and severe allergies would be much rarer as peoples immune systems would be more regularly challenged.
 
Most bacterial and viral diseases, you develop immunity to them once you get them. This is perfectly clear once medicine is developed enough to reliably identify diseases, which admittedly happened amazingly late iOTL. From there, vaccines are obvious. Can vaccines be delayed a century or two? Probably.

But once you've got germ theory established...

The only way to avoid this is with a massive slowing down of knowledge, so vaccines were the least of your changes, or with an evolutionary change so most diseases we're protozoan (like malaria), or massive complexes of related, but non cross immunizing strains (like flus and colds). But that kind of evolutionary PoD goes in the ASB sub forum.

So. No, i don't think what you ask for is feasible.
 
Top