WHAT IS CIRCULATING VACCINE DERIVED POLIO?

Posted by PDG Murray Verso, End Polio Now Coordinator
Over the past 40 years, Rotary and its partners in the Global Polio Eradication Initiative have reduced the incidence of poliomyelitis by 99%. Thanks to our eradication efforts more than 20 million children have avoided the devastating effects of polio.

 

With only 12 cases of wild polio virus in 2023 (6 in Afghanistan and 6 in Pakistan) and no cases for the past 5 months, we are very close to seeing the end of endemic polio. However, in recent years outbreaks of circulating vaccine derived polio virus (cVDPV) have become a major challenge to achieving eradication.

Unlike wild polio virus which occurs in nature, vaccine derived polio (aka variant polio) are non-wild variants that sometimes emerge in populations where children have not been vaccinated. In these areas of under immunization, if the weakened form of polio virus contained in oral polio vaccine (OPV) circulates for an extended time, this strain can genetically change to one that can cause paralysis. OPV itself does not cause polio.

cVDPV outbreaks occur in geographical regions where routine immunizations and door-to-door campaigns have failed to reach some children for many years. These could occur because of

  • weak immunization programs in poorly resourced countries
  • civil unrest
  • misinformation
  • mobile populations

The best way to minimize the risk of cVDPV or variant polio is to maintain high vaccination rates amongst children.

Stopping cVDPV outbreaks is a major priority for the GPEI and is outlined in its 2022-26 Strategy. When an outbreak occurs, it is vital that countries respond quickly to stop it spreading further.

A key weapon in the fight to combat cVDPV, is the novel oral polio vaccine type 2 (nOPV2) released in 2021 under the WHO’s Emergency Use Listing procedure. It is much more genetically stable and therefore less likely to be associated with cVDPV2 outbreaks than the older versions of OPV. As of December 2023, approximately 1 billion doses of the vaccine have been administered across 35 selected countries, predominantly in the African region which is most affected by cVDPV2 outbreaks.

In late December 2023, the World Health Organization issued its prequalification approval for the new vaccine. This will enable additional countries to access the vaccine more easily to respond to outbreaks of type 2 variant poliovirus (cVDPV2)

nOPV2 is helping us make valuable headway against cVDPV2 outbreaks, and with the ongoing support from our global partners, donors and leaders of polio-affected countries, we can stop all forms of polio for good. 

PDG Murray Verso is End Polio Now Coordinator

(Photo from PEXELS)