VAPP or vaccine-associated paralytic polio are cases of polio that are actually caused by the polio vaccine.
Very rarely, the attenuated (weakened) virus in the oral polio vaccine can revert to a form that can cause the person who was vaccinated or their close contact to actually develop polio.
It should not be confused with cVDPV or circulating vaccine-derived polio virus. With cVDPV, the original strain of attenuated vaccine virus reverts to a form that can not only cause polio, but can also spread from one person to another, causing outbreaks. Fortunately, these outbreaks are very rare.
Vaccine-Associated Paralytic Polio
How rarely? VAPP only occurs in about 1 in every 1.27 million children receiving their first dose of OPV.
Can’t we just stop using the live, oral polio vaccine?
Although a serious side effect of the vaccine, the vaccine’s benefit clearly outweighs the risk of VAPP while polio is endemic (lots of cases) in a region, after all, without the vaccine, hundreds of thousands of children would get polio and would be paralyzed.
In polio-free countries, the risk of VAPP becomes greater than the risk of polio though, and they move to the inactivated polio vaccine. That helps prevent a situation in which the polio vaccines actually causes more cases of polio than wild type polio viruses.
Eventually, all countries will move to the IPV vaccine as we move closer to polio eradication. We came one step closer to that point in April 2016 when all countries that were still using the oral polio vaccine switched from trivalent OPV to bivalent OPV for their routine immunization programs. This should eliminate up to 38% of cases of VAPP!
What To Know About VAPP
VAPP or vaccine-associated paralytic polio is a rare side effect of the oral polio vaccine.
More Information About VAPP
- Oral polio vaccine (OPV) cessation
- Replacing trivalent OPV with bivalent OPV
- Polio Eradication and Endgame Strategic Plan 2013–2018
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