Eradication - the final stages

How do we reach the final goal of complete eradication? A polio free world is in sight as a major new step forward is taken in 155 countries.

The Global Polio Eradication Initative (GPEI) has set out an Endgame Strategy to complete the final stages of worldwide polio eradication.

Stage 1
Detect and stop the transmission of wild polio virus – whilst Afghanistan & Pakistan are the only two endemic countries, immunization activities continue in up to 60 countries including increased levels of surveillance.
Stage 2
Strengthen routine immunization – we need to strengthen health services so that even we stop immunization campaigns after the world is certified polio-free, children have access to vaccines
Stage 3
Switch from oral polio vaccine to intravenous polio vaccine to prevent isolated cases of vaccine derived polio
Stage 4
Destroy most remaining samples of polio virus – once polio is eradicated, we won’t want to risk accidental reintroduction.

News of progress

Polio-Free World in Sight as Largest Vaccine Rollout is completed in 2017

April 17th 2017 marked the beginning of the largest and fastest globally coordinated rollout of a vaccine into routine immunization programs in history. Between 17 April and 1 May, 155 countries and territories around the world stopped using the trivalent oral polio vaccine (tOPV), which protects against all three strains of wild poliovirus, and replaced it with bivalent OPV (bOPV), which protects against the remaining two wild polio strains, types 1 and 3. This effort will provide better protection for children against polio, particularly those most vulnerable to infection.

This transition, referred to as the global vaccine “switch,” is possible because type 2 wild polio has been eradicated. The switch has been recommended by the Strategic Advisory Group of Experts on Immunization and endorsed by the World Health Assembly as a critical component of the polio endgame strategy.

The oral polio vaccine (OPV) has been used to stop polio in most of the world. On very rare occasions in under-immunized populations, the live weakened virus contained in OPV can mutate and cause circulating vaccine-derived polioviruses (cVDPV). More than 90% of cVDPV cases in the last 10 years have been caused by the type 2 vaccine strain. Withdrawing tOPV and replacing it in routine immunization programs with bOPV will eliminate the risks associated with the type 2 vaccine strain and, just as importantly, boost protection against the two remaining wild strains of the virus.

The switch had to be globally synchronized because if some countries continue to use tOPV it could increase the risk of the spread of type 2 poliovirus to those no longer using tOPV. The switch is the first major step toward the eventual removal of all OPV after wild polio transmission has been stopped.

In countries at higher-risk of a polio outbreak, a dose of inactivated polio vaccine (IPV) has been added to routine immunization schedules, in addition to bOPV, to further boost immunity. To protect against the very small risk of an outbreak of cVDPV type 2 after the switch, a global stockpile of monovalent OPV (mOPV) type 2 is ready to be dispatched if an outbreak occurs.