In 5-10% of cases, however, the virus affects the nerves, paralysing the legs in particular; sometimes it reaches the lungs. First, what is being eradicated is wild polio – ie, naturally occurring, of which three strains exist. It’s still possible to get vaccine-derived polio, where the much-diluted active components spread through an under-vaccinated community and, in rare cases, revert to the full-blown disease. Wild type 2 polio was eradicated in 1999, and the active version duly removed from the droplet vaccine in 2016. However, type 2 vaccine-derived polio continues to circulate.

Source: The Guardian August 30, 2020 17:26 UTC