With polio near eradication, global switch to a new vaccine set to begin
- Governments, health authorities, and humanitarian organizations across the globe will soon begin a synchronized switch to a new type of polio vaccine, while simultaneously destroying the older versions. Planned by the Global Polio Eradication Initiative and the World Health Organization, the switch is set to begin April 17 in over 150 countries, according to the New York Times.
- The new bivalent oral vaccine will replace the existing trivalent vaccine and will no longer immunize people against type 2 polio, which was eradicated in 1999. With the removal of the type 2 component, the new vaccine will have a lower risk of side effects and boost immunity against types 1 and 3.
- Polio is almost eradicated. In 1988, there were 350,000 cases, compared with only 74 cases in 2015. All of the cases last year were in Afghanistan and Pakistan.
The switch will necessitate moving hundreds of millions of doses of new vaccines to refrigerated warehouses, while old vaccines are systematically destroyed. Acceptable methods for destroying vaccines include incineration, boiling, autoclaving, bleaching or burying in concrete-sealed containers.
Trivalent polio vaccines are no longer necessary with the eradication of type 2 polio and are in fact problematic because of their contribution to a phenomenon known as vaccine-associated paralytic polio (VAPP), and the related circulated vaccine-derived poliovirus (cVDPV).
Within the last 10 years, there have been 725 cases of VAPP and 90% of those cases were caused by mutated type 2 poliovirus originating from the attenuated strain in the vaccine. With type 2 polio no longer an infectious threat, the inclusion of this component poses an additional risk.
However, the risk could be amplified if there is any type 2 polio lingering in the vaccine pool, since newly vaccinated children will now have no protection against type 2 polio. This raises the importance of ensuring all old vaccines are destroyed.
The global switch will be a logistical challenge but could hasten the global end of polio.