Polio the disease caused by polio virus could be eradicated with widespread and continuous vaccination.
The problem is the current vaccine used in most places around the world is an attenuated live virus vaccine.
It gives the recipient immunity by infecting them with a strain that doesn’t cause disease in most people but is still able to replicate in the gut and spread to others and eventually reverts to being able to cause disease. So anyone who isn’t vaccinated can still get the reverted vaccine strain. The most common cause of polio outbreaks now is the vaccine strain.
In rich countries they use an inactivated vaccine that works great against disease and can’t become virulent but is expensive, requires more infrastructure for delivery (needles etc), and doesn’t give enough immunity to prevent spreading the virus if infected.
There are possible solutions to all of these problems but they require research and the eradication campaigners are making research more and more difficult by restricting which labs can work on polio research.
The podcast TWiV is hosted by the guy who first figured out the Polio virus genome and they frequently discuss it. The episode below is about a new attenuated vaccine that was recently created with hopes of not reverting but even it has reverted in some small number of cases.
0: https://asm.org/podcasts/twiv/episodes/driven-to-immunodistr...