The World Health Organization (WHO) convened the 40th meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) on November 6, 2024. The committee, composed of members, advisers, and representatives from affected countries, reviewed data on wild poliovirus (WPV1) and circulating vaccine-derived polioviruses (cVDPV) as part of global efforts to achieve eradication targets for WPV1 by 2027 and cVDPV2 by 2029.
Wild Poliovirus Update
Current Status
The committee reported 51 new WPV1 cases since its last meeting, bringing the total for 2024 to 62. These include 17 cases in Afghanistan and 34 in Pakistan, representing significant increases compared to 2023:
- Afghanistan: A 283% rise in paralytic cases compared to 2023, with environmental samples also increasing (84 in 2024 vs. 62 in 2023).
- Pakistan: A 550% rise in cases, with 402 WPV1-positive environmental samples in 2024, compared to 126 in 2023.
Geographic Spread
WPV1 transmission has intensified in cross-border regions between Afghanistan and Pakistan, particularly in Quetta (Pakistan) and Afghanistan’s southern region. Historic reservoirs like Karachi and Peshawar are also showing signs of resurgence.
Vaccination Campaigns
Afghanistan and Pakistan have intensified synchronized vaccination efforts:
- Afghanistan conducted two nationwide and four sub-national rounds.
- Pakistan held two nationwide and six sub-national rounds.
However, challenges persist:
- Afghanistan: A shift to site-to-site campaigns, which exclude house-to-house vaccination, raises concerns about access to children, particularly girls.
- Pakistan: Insecurity, attacks on health workers, and boycotts have disrupted campaigns, leaving up to 700,000 children unvaccinated in some areas.
Population displacement, including the return of undocumented migrants from Pakistan to Afghanistan, adds complexity, increasing the risk of cross-border spread. Vaccination efforts at border crossings and enhanced coordination with organizations like IOM and UNHCR are being employed to mitigate these risks.
Accidental WPV3 Exposure in France
The committee acknowledged a recent WPV3 exposure at a manufacturing facility in France. Swift and effective containment measures prevented any spread, emphasizing the importance of adhering to WHO’s Global Action Plan for Poliovirus Containment.
Circulating Vaccine-Derived Poliovirus (cVDPV)
2024 Overview
So far in 2024, 190 cVDPV cases have been reported:
- 182 cVDPV2 cases: Nearly half (85 cases) occurred in Nigeria.
- Eight cVDPV1 cases: Seven in the Democratic Republic of the Congo (DRC) and one in Mozambique.
This is a significant reduction compared to 2023, which recorded 529 cases (395 cVDPV2 and 134 cVDPV1).
Geographic Spread
New detections of cVDPV2 occurred in Cameroon, Djibouti, French Guiana, Ghana, occupied Palestinian territory (Gaza), Spain, and Zimbabwe.
- In Gaza, one paralytic case and 11 positive environmental samples were reported amid humanitarian challenges. Nearly 600,000 children were vaccinated in response.
- Guinea and French Guiana recorded cVDPV3 cases, marking the first outbreaks of this strain since 2022.
Progress and Challenges
- Madagascar: Encouraging progress, with no cVDPV1 cases reported for over a year.
- DRC: One new cVDPV1 emergence was detected in Tshopo province.
- Northern Yemen: Insecurity and conflict prevent immunization, mirroring challenges in northern Nigeria, Somalia, and eastern DRC.
The committee highlighted the novel oral polio vaccine (nOPV2), which shows improved genetic stability and reduced neurovirulence compared to previous vaccines, as a promising tool for controlling cVDPV2.
Summary and Recommendations
The committee concluded that WPV1 transmission remains geographically confined to Afghanistan and Pakistan but noted an increase in spread and intensity. Similarly, cVDPV outbreaks continue to occur due to a combination of under-immunization, insecurity, and displacement, particularly in conflict-affected areas.
The committee urged continued efforts to address operational challenges, enhance vaccination coverage, and strengthen surveillance to meet eradication targets. Close collaboration between governments, international organizations, and local communities remains essential to achieving these goals.
