Which 39 countries reported vaccine-derived poliovirus cases during the 2023 to 2024 period?

Vaccine-derived poliovirus (VDPV) occurs when the weakened virus in the oral polio vaccine mutates and spreads in communities with low vaccination coverage. A specific report from the Global Polio Eradication Initiative tracked these cases during the period from January 2023 to June 2024 ⁵. This surveillance found that 39 countries reported at least one case of VDPV during that time ⁵.

What the research says

The primary data on the specific count of 39 countries comes from a report covering the January 2023 to June 2024 surveillance period ⁵. This number reflects the global spread of the virus in areas where immunity is low, distinct from wild poliovirus which was detected in Pakistan and Afghanistan during parts of this timeframe ⁴⁹.

Previous years showed similar trends, with 36 countries reporting circulating VDPV cases between January 2021 and May 2023 ⁹. In 2021 to 2022, outbreaks of circulating vaccine-derived polioviruses were documented globally ⁷. Specific types of VDPV, such as type 2, have been detected in wastewater in European cities ⁶, while type 1 cases have been reported in African regions where the virus had previously been eliminated ⁸.

These reports highlight that despite the eradication of wild poliovirus types 2 and 3, the risk of VDPV remains a significant challenge to global polio eradication efforts ⁹. The shift to using inactivated poliovirus vaccines in some areas is a response to this ongoing risk ⁹.

What to ask your doctor

• How does the risk of vaccine-derived poliovirus differ from wild poliovirus in my area?
• What are the current vaccination recommendations for my family given recent VDPV reports?
• Are there specific travel precautions I should take if visiting regions with recent polio cases?
• How does the switch to bivalent oral polio vaccine affect protection against VDPV type 2?