When I started my scientific career by working on polio vaccines over 30 years ago, we were already thinking about newer, safer vaccines. Although polio eradication remains tantalizingly out of reach, we are close enough now to think in detail about what needs to be done after eradication. It won’t be as simple as with smallpox – polio vaccination will need to continue.
New Strains Intended for the Production of Inactivated Polio Vaccine at Low-Containment After Eradication. (2015) PLoS Pathog 11(12): e1005316. doi:10.1371/journal.ppat.1005316
New polio vaccines will be needed to safeguard global eradication: Sabin strains are known to evolve to fill the niche left by wild-strains so their long-term use is incompatible with eradication; most current inactivated vaccine is made from wild polioviruses so that production presents a significant biosecurity risk. We have developed new strains for Inactivated Polio Vaccine (IPV) production with negligible risk to the human population should they escape. Sabin’s live-attenuated vaccines are variants of wild strains selected by the use of unnatural cell substrates, hosts and growth conditions. Unsurprisingly these variants evolve back towards wild-type properties during replication in, and transmission between, their natural hosts. An understanding of the molecular basis of these pathways led us to design novel vaccine strains that are very highly attenuated and arguably cannot replicate in people and whose opportunities for reversion during replication in cell culture are severely restricted. At the same time, the strains can feasibly be produced on a large-scale and they are as immunogenic as current IPV. These attributes allow for safe vaccine production in the post-eradication world.