Polio IHR Emergency Committee Holds 40th Meeting

The fortieth meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) on the international spread of poliovirus was convened by the WHO Director-General on 6 November 2024 with Committee members and advisers meeting via video conference with affected countries, supported by the WHO Secretariat. The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPV) in the context of the global target of interruption and certification of WPV1 eradication by 2027 and interruption and certification of cVDPV2 elimination by 2029. Technical updates were received about the situation in Afghanistan, Cameroon, France, Ghana, Indonesia, Nigeria, occupied Palestinian territory (oPt), Pakistan, Spain and Zimbabwe.

Wild poliovirus

Since the last Emergency Committee meeting, 51 new WPV1 cases were reported – 17 from Afghanistan and 34 from Pakistan – bringing the total to 62 in 2024. This represents a 283% increase in paralytic cases in Afghanistan and a 550% increase in Pakistan compared to all of 2023. The number of WPV1 positive environmental samples in Pakistan in 2024 is 402 compared to 126 during all of 2023. The number of WPV1 positive environmental samples in Afghanistan in 2024 is 84 compared to 62 in all of 2023.

There has been an upward trend of WPV1 detection in Pakistan since mid-2023, initially in the environmental samples and later also in paralytic polio cases, mostly from Khyber Pakhtunkhwa (KP), Sindh and Balochistan provinces. In Afghanistan, there is increased WPV1 detection in the environmental samples and paralytic cases, mainly in the South Region since late 2023. The Committee noted the WPV1 geographic spread in both the endemic countries and that most of the newly infected provinces in 2024 had not reported WPV1 cases in recent years (before 2024). The Committee, however, noted that the most intense WPV1 transmission is in the southern cross border epidemiological corridor comprising of Quetta Block of Pakistan and South Region of Afghanistan. Moreover, WPV1 transmission is seemingly re-establishing in historical core reservoirs of Karachi and Peshawar of Pakistan. Review of the molecular epidemiology indicates that there has been progressive elimination of the genetic cluster 'YB3C' in 2022 and 2023, with its last detection in November 2023 in Bannu district of Khyber Pakhtunkhwa province of Pakistan. However, there has been persistent transmission of YB3A genetic cluster since May 2022, resulting in its split into two: YB3A4A and YB3A4B. The YB3A4A is a shared cluster in the northern and southern cross-border corridors across Afghanistan and Pakistan, while the YB3A4B is mainly active in Pakistan.

Both Afghanistan and Pakistan continue to implement an intensive and synchronized campaign schedule focusing on improved vaccination coverage in the endemic zones and effective and timely response to WPV1 detections elsewhere in each country. Both countries implemented two nationwide rounds each in 2024 so far; Afghanistan implemented an additional four and Pakistan an additional six sub-national vaccination rounds. After very encouraging progress towards implementing house-to-house campaigns in all of Afghanistan during the first half of 2024, Afghanistan programme has recently gone back to implementing site-to-site modality campaigns. The Committee was concerned about this recent development, since site-to-site campaigns are not able to reach all the children in Afghanistan especially those of younger age and girls, which may lead to a further upsurge of WPV1 with geographical spread in Afghanistan and beyond. In Pakistan, the campaign quality in the endemic zone of South KP and historic WPV1 reservoirs continues to face challenges relating to operational implementation and increasing insecurity (including attacks on health works) particularly in the Khyber Pakhtunkhwa and Balochistan provinces. Despite some recent progress in the endemic South KP in Pakistan, there are concerning numbers of missed children during the recent campaigns (ranging from 5000 to 700 000) due to insecurity, boycotts, and programme quality issues. Key AFP surveillance performance indicators are not meeting the targets in some of the districts of South KP of Pakistan. In addition to seasonal movement patterns within and between the two endemic countries, the continued return of undocumented migrants from Pakistan to Afghanistan compounds the challenges faced. The scale of the displacement increases the risk of cross-border poliovirus spread as well as spread within both the countries. This risk is being managed and mitigated in both countries through vaccination at border crossing points and the updating of micro-plans in the districts of origin and return. The programme continues to closely coordinate with IOM and UNHCR.

In summary, the available data indicate that globally transmission of WPV1 is geographically limited to the two WPV1 endemic countries; however, there has been geographical spread and intensifying transmission within the two endemic countries in 2024.

Wild poliovirus type-3 accidental exposure in France

The Committee noted the recent incident of an accidental WPV3 exposure in a manufacturing plant in France and appreciated the immediate and effective response measures taken by the French authorities to prevent any spread. The Committee reinforced the importance of ensuring poliovirus containment measures as per the WHO Global Action Plan for Poliovirus Containment and recommendations of the Global Certification Commission on Poliomyelitis Eradication.

Circulating vaccine derived poliovirus (cVDPV)

In 2024, there have been 190 cVDPV cases, of which 182 are cVDPV2 and eight are cVDPV1. Additionally, 177 environmental samples were positive for cVDPV, all type 2. Of the 182 cVDPV2 cases in 2024, 85 (46%) have occurred in Nigeria. Of the eight cVDPV1 cases in 2024, seven were reported from DR Congo and one from Mozambique.

A total of 529 cases have been confirmed with cVDPV in all of 2023, of which 395 are cVDPV2 and 134 are cVDPV1. Of the 529 cVDPV cases reported in 2023, 226 (43%) have occurred in the DR Congo.

Since the last meeting of the Emergency Committee, Cameroon, Djibouti, French Guiana (France), Ghana, oPt, Spain, and Zimbabwe reported new cVDPV2 detections. Amidst the ongoing insecurity and humanitarian challenges, the oPt (Gaza) reported 11 cVDPV2 positive environmental samples and one paralytic case between June and October 2024. The Committee appreciated the ongoing outbreak response implementation in Gaza reaching nearly 600 000 children during the first campaign, despite the very challenging situation.

In 2024, the total number of circulating cVDPV2 emergence groups detected to date is 24, compared to 27 in 2023, 22 in 2022, 29 in 2021, 36 in 2020, and 44 in 2019. Of the 24 emergence groups circulating in 2024, eight are newly detected this year, all derived from the novel OPV2 vaccine. There have now been 23 nOPV2 derived cVDPV2 emergences since 2021. The Committee noted that the nOPV2 vaccine continues to demonstrate significantly higher genetic stability and substantially lower likelihood of reversion to neurovirulence relative to Sabin OPV2.

A total of eight cVDPV1 cases have been reported in 2024, seven in the Democratic Republic of the Congo and one in Mozambique. This compares to 134 cVDPV1 cases in all of 2023 (106 in Democratic Republic of the Congo, 24 in Madagascar, four in Mozambique), representing a 94% reduction in the global cVDPV1 paralytic burden from 2023. However, one new emergence has been reported from the Tshopo province in the Democratic Republic of the Congo (RDC-TSH-3). This is the first cVDPV1 emergence reported since September 2022. The committed noted encouraging progress in Madagascar towards interrupting local cVDPV1 transmission, with no detections for more than 12 months.

The Committee noted that two cVDPV3 outbreaks have recently been reported for the first time since March 2022; in French Guiana (a French territory located in the South America) and Guinea in the African Region. French Guiana reported three cVDPV3 positive environmental samples while Guinea reported three paralytic cases.

The Committee noted that much of the risk for cVDPV outbreaks can be linked to a combination of inaccessibility, insecurity, a high concentration of zero dose and under-immunized children along with continued population displacement. These factors are currently most evident in northern Yemen where response immunization has not yet happened due to insecurity and conflict as well as northern Nigeria, south-central Somalia, eastern DR Congo and oPt.

Conclusion

The Committee unanimously agreed that the risk of international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC) and recommended the extension of Temporary Recommendations for a further three months. The Committee considered the following factors in reaching this conclusion:

Ongoing risk of WPV1 international spread:

Based on the following factors, there remains the risk of international spread of WPV1:

• Spread of WPV1 transmission back into formerly endemic areas and core reservoirs of Afghanistan (South) and Pakistan (Karachi, Peshawar, Quetta Block) as well as other areas in the two countries that were without any WPV1 detection for prolong periods of time; representing a significant risk to the gains made during the last two years.
• That WPV1 transmission has been re-established in the south region of Afghanistan and the Peshawar, Karachi, and Quetta Blocks in Pakistan.
• This intensifying WPV1 transmission in both endemic countries during the early low transmission season indicates sizeable cohort of unimmunized and under-immunized children.
• Lack of house-to-house vaccination campaigns in Afghanistan represents a major risk of further WPV1 spread and intensification of its transmission.
• Certain geographies and population pockets in the epidemiologically critical areas of Pakistan continue to have inconsistent campaign quality and substantial number of unimmunized and under-immunized children due to insecurity (including attacks on health workers) and operational gaps.
• High-risk mobile populations in Pakistan represent a specific risk of international spread to Afghanistan in particular, compounded by ongoing significant movement of returnees from Pakistan into several provinces of Afghanistan.

Ongoing risk of cVDPV international spread:

Based on the following factors, the risk of international spread of cVDPV appears to remain high:

• Ongoing cross border spread including into newly re-infected countries and territories.
• Continued cVDPV2 transmission in the critical areas of Nigeria, with 46% of the global cVDPV2 cases in 2024 and its potential to amplify the transmission.
• The cVDPV2 transmission in the Horn of Africa seems to be intensifying. The Horn of Africa countries continue to face humanitarian and health emergencies making it challenging to implement high-quality vaccination campaigns in a timely manner.
• There is a large pool of unimmunized susceptible children in the Northern Governorates of Yemen.
• The ever-widening gap in population intestinal mucosal immunity in young children since the withdrawal of OPV2 in 2016, as well as high concentration of zero dose children in certain areas.
• Despite the decreasing number of cVDPV1 cases, a new emergence was detected in DR Congo, indicating a population immunity gap.
• Recent resurgence of cVDPV3 after more than two years, infecting French Guiana and Guinea.
• Ongoing insecurity and conflict in many areas that are the source of cVDPV transmission.

Contributing factors include:

• Weak routine immunization: Many countries have weak immunization systems that can be further impacted by humanitarian emergencies including conflict and protracted complex emergencies. This poses a growing risk, leaving populations in these fragile states vulnerable to polio outbreaks.
• Lack of access: Inaccessibility continues to be a major risk, particularly in northern Yemen and Somalia which have sizable populations that have been unreached with polio vaccine for extended periods of more than a year.

Risk categories

The Committee provided the Director-General with the following advice aimed at reducing the risk of international spread of WPV1 and cVDPVs, based on the risk stratification as follows:

1. States infected with WPV1, cVDPV1 or cVDPV3.
2. States infected with cVDPV2, with or without evidence of local transmission.
3. States previously infected by WPV1 or cVDPV within the last 24 months.

Criteria to assess States as no longer infected by WPV1 or cVDPV:

• Poliovirus Case: 12 months after the onset date of the most recent case PLUS one month to account for case detection, investigation, laboratory testing and reporting period OR when all reported AFP cases with onset within 12 months of last case have been tested for polio and excluded for WPV1 or cVDPV, and environmental or other samples collected within 12 months of the last case have also tested negative, whichever is the longer.
• Environmental or other isolation of WPV1 or cVDPV (no poliovirus case): 12 months after collection of the most recent positive environmental or other sample (such as from a healthy child) PLUS one month to account for the laboratory testing and reporting period.
• These criteria may be varied for the endemic countries, where more rigorous assessment is needed in reference to surveillance gaps.

Once a country meets these criteria as no longer infected, the country will be remain on a 'watch list' for a further 12 months for a period of heightened monitoring. After this period, the country will no longer be subject to Temporary Recommendations.

TEMPORARY RECOMMENDATIONS

States infected with WPV1, cVDPV1 or cVDPV3 with potential risk of international spread

(as of data available at WHO HQ on 22 October 2024)

WPV1

Afghanistan most recent detection 23 Sep 2024

Pakistan most recent detection 01 Oct 2024

cVDPV1

Mozambique most recent detection 17 May 2024

DR Congo most recent detection 27 Apr 2024

cVDPV3

French Guiana (France) most recent detection 06 Aug 2024

Guinea most recent detection 12 Sep 2024

These countries should:

• Officially declare, if not already done, at the level of head of state or government, that the interruption of poliovirus transmission is a national public health emergency and implement all required measures to support polio eradication; where such declaration has already been made, this emergency status should be maintained as long as the response is required.
• Ensure that all residents and long­term visitors (> four weeks) of all ages, receive a dose of bivalent oral poliovirus vaccine (bOPV) or inactivated poliovirus vaccine (IPV) between four weeks and 12 months prior to international travel.
• Ensure that those undertaking urgent travel (within four weeks), who have not received a dose of bOPV or IPV in the previous four weeks to 12 months, receive a dose of polio vaccine at least by the time of departure as this will still provide benefit, particularly for frequent travelers.
• Ensure that such travelers are provided with an International Certificate of Vaccination or Prophylaxis in the form specified in Annex 6 of the IHR to record their polio vaccination and serve as proof of vaccination.
• Restrict at the point of departure the international travel of any resident lacking documentation of appropriate polio vaccination. These recommendations apply to international travelers from all points of departure, irrespective of the means of conveyance (road, air and / or sea).
• Further intensify cross­border efforts by significantly improving coordination at the national, regional and local levels to substantially increase vaccination coverage of travelers crossing the border and of high risk cross­border populations. Improved coordination of cross­border efforts should include closer supervision and monitoring of the quality of vaccination at border transit points, as well as tracking of the proportion of travelers that are identified as unvaccinated after they have crossed the border.
• Further intensify efforts to increase routine immunization coverage, including sharing coverage data, as high routine immunization coverage is an essential element of the polio eradication strategy, particularly as the world moves closer to eradication. Countries which have not yet introduced IPV2 into their schedules should urgently implement this. Once available, countries should also consider introducing the hexavalent vaccine now approved by Gavi.
• Maintain these measures until the following criteria have been met: (i) at least six months have passed without new infections and (ii) there is documentation of full application of high-quality eradication activities in all infected and high-risk areas; in the absence of such documentation these measures should be maintained until the state meets the above assessment criteria for being no longer infected.
• Provide to the Director-General a regular report on the implementation of the Temporary Recommendations on international travel.

States infected with cVDPV2, with or without evidence of local transmission*:

(as of data available at WHO HQ on 22 October 2024)

1. Algeria most recent detection 14 Aug 2024
2. Angola most recent detection 24 Aug 2024
3. Benin most recent detection 18 May 2024
4. Burkina Faso most recent detection 12 Dec 2023
5. Cameroon most recent detection 02 Aug 2024
6. Central African Republic most recent detection 07 Oct 2023
7. Chad most recent detection 30 Aug 2024
8. Rep. Congo most recent detection 07 Dec 2023
9. Côte d'Ivoire most recent detection 23 Apr 2024
10. Democratic Republic of the Congo most recent detection 14 Jul 2024
11. Djibouti most recent detection 08 Sep 2024
12. Egypt most recent detection 01 Aug 2024
13. Equatorial Guinea most recent detection 26 Mar 2024
14. Ethiopia most recent detection 22 Jul 2024
15. Gambia most recent detection 15 Feb 2024
16. Ghana most recent detection 20 Aug 2024
17. Guinea most recent detection 12 Jun 2024
18. Indonesia most recent detection 10 Jul 2024
19. Kenya most recent detection 31 Jul 2024
20. Liberia most recent detection 08 Jun 2024
21. Mali most recent detection 02 Jan 2024
22. Mauritania most recent detection 13 Dec 2023
23. Mozambique most recent detection 05 Mar 2024
24. Niger most recent detection 17 Sep 2024
25. Nigeria most recent detection 07 Sep 2024
26. occupied Palestinian territory (oPt) most recent detection 05 Sep 2024
27. Senegal most recent detection 02 May 2024
28. Sierra Leone most recent detection 28 May 2024
29. Somalia most recent detection 05 Jun 2024
30. South Sudan most recent detection 02 Sep 2024
31. Spain most recent detection 16 Sep 2024
32. Sudan most recent detection 24 Jan 2024
33. Uganda most recent detection 07 May 2024
34. United Republic of Tanzania most recent detection 20 Nov 2023
35. Yemen most recent detection 25 Jun 2024
36. Zimbabwe most recent detection 25 Jun 2024

States that have had an importation of cVDPV2 but without evidence of local transmission should:

• Officially declare, if not already done, at the level of head of state or government, that the prevention or interruption of poliovirus transmission is a national public health emergency.

• Undertake urgent and intensive investigations and risk assessment to determine if there has been local transmission of the imported cVDPV2, requiring an immunization response

• Noting the existence of a separate mechanism for responding to type 2 poliovirus infections, Members States should request vaccines from the global novel OPV2 stockpile

• Further intensify efforts to increase routine immunization coverage, as high routine immunization coverage is an essential element of the polio eradication strategy, particularly as the world moves closer to eradication. Countries which have not yet introduced IPV2 into their schedules should urgently implement this. Once available, countries should also consider introducing the hexavalent vaccine, now approved by Gavi.
• Intensify national and international surveillance regional cooperation and cross­border coordination to enhance surveillance for prompt detection of poliovirus.

States with local transmission of cVDPV2, with risk of international spread, in addition to the above measures, should:

• Encourage residents and long­term visitors to receive a dose of IPV four weeks to 12 months prior to international travel.

• Ensure that travellers who receive such vaccination have access to an appropriate document to record their polio vaccination status.
• Intensify regional cooperation and cross­border coordination to enhance surveillance for prompt detection of poliovirus, and vaccinate refugees, travellers and cross­border populations.

For both sub-categories:

• Maintain these measures until the following criteria have been met: (i) at least six months have passed without the detection of circulation of VDPV2 in the country from any source, and (ii) there is documentation of full application of high quality eradication activities in all infected and high risk areas; in the absence of such documentation these measures should be maintained until the state meets the criteria of a 'state no longer infected'.
• At the end of 12 months without evidence of transmission, provide a report to the Director-General on measures taken to implement the Temporary Recommendations.

States no longer polio infected, but previously infected by WPV1 or cVDPV within the last 24 months and which remain vulnerable to re-infection by WPV or cVDPV (as of data available at WHO HQ on 22 October 2024)

WPV1

country last virus date

cVDPV

Country Last virus date

1. Botswana cVDPV2 25 Jul 2023
2. Burundi cVDPV2 15 Jun 2023
3. Israel cVDPV2 13 Feb 2023
4. Madagascar cVDPV1 16 Sep 2023
5. Malawi cVDPV2 02 Jan 2023
6. The United Kingdom cVDPV2 08 Nov 2022
7. Zambia cVDPV2 06 Jun 2023

These countries should:

• urgently strengthen routine immunization to boost population immunity;

• enhance surveillance quality, including considering introducing or expanding supplementary methods such as environmental surveillance, to reduce the risk of undetected WPV1 and cVDPV transmission, particularly among high-risk mobile and vulnerable populations;

• intensify efforts to ensure vaccination of mobile and cross­border populations, Internally Displaced Persons, refugees and other vulnerable groups;

• enhance regional cooperation and cross border coordination to ensure prompt detection of WPV1 and cVDPV, and vaccination of high-risk population groups; and

• maintain these measures with documentation of full application of high-quality surveillance and vaccination activities.

Additional considerations

The Committee noted that GPEI Polio Oversight Board (POB) in its recent meeting in mid-October 2024, revised the timeline for the GPEI Strategy 2022 – 2026, up to 2029. The strategy under the revised timeline, aims to stopping WPV1 transmission in Pakistan and Afghanistan by end-2025 and certification of WPV1 eradication by end-2027; and stopping cVDPV2 outbreaks globally by end-2026 and certification cVDPV2 elimination by 2029. The bOPV Cessation will be considered after certification of eradication of WPV1 and certification of elimination of cVDPV2 by the Global Certification Commission on Poliomyelitis Eradication.

The Committee expressed concern about the intensifying WPV1 transmission in Afghanistan and Pakistan with significant increase in the number of paralytic cases and geographic spread in 2024. Consequent to persistent WPV1 transmission, the YB3A genetic cluster of WPV1 has split into two, indicating significant number of under-immunized children in both the remaining endemic countries. Continuing WPV1 transmission despite the ongoing campaigns implementation indicates the need for an in-depth programme review and adjustment in current programme strategies. The review should inform the programme planning and implementation in the crucial upcoming low transmission season from December 2024 through May 2025.

The Committee is concerned about the inability to implement house-to-house campaigns and very low engagement of women health workers in Afghanistan, putting infants and young children especially the girls, at high risk of missing polio vaccination. This situation may jeopardize all the gains made in Afghanistan over the last two years, including in the East Region where polio epidemiology has been seemingly improving during the last few months.

The Committee noted the high-level political commitment for polio eradication in Afghanistan and Pakistan. The Committee urged that the political commitment must translate into meaningful steps at the operational level to enhance community engagement and implement high-quality vaccination campaigns to stop the current intense WPV1 transmission and avert the risk of national and international spread. Specifically in Afghanistan the Committee recommended resumption of house-to-house campaigns and employment of more female vaccinators to enhance community acceptability.

The Committee noted the ongoing transmission of cVDPV in the African Region; particularly in northern Nigeria, where the transmission has lately intensified. The reports about continued sub-optimal quality vaccination campaigns and lack of community engagement are concerning for the Committee. The Committee noted the recent review and planning exercise of the Nigeria polio programme and urged to immediately put in place the plans to address the challenges in northern Nigeria. Though, the number of cVDPV cases have declined in DR Congo in 2024, the Committee considers that the country is still at high-risk of continuing outbreaks and needs to further boost population immunity through high-quality vaccination efforts. The Committee is encouraged by the improving cVDPV1 situation in the African Region; however, expressed concern about the recent detection of a new cVDPV1 emergence in DR Congo, indicating some population pockets with low immunity.

The Committee expressed concern about the inability to implement immunization response in the northern Yemen, with continued reporting of cases. The Committee is also concerned about the surveillance related challenges in northern Yemen. The committee is encouraged by the coordinated immunization response in Gaza and appreciated the efforts of all stakeholders towards implementing the response.

The committee noted the detection of cVDPV3 in Guinea and French Guiana after more than two years and urged timely and high-quality surveillance and immunization response to stop these outbreaks.

The committee noted that many of the cVDPV infected countries remain conflict affected, disrupting routine immunization as well as polio vaccination campaigns. The committee also noted that other health emergencies and disease outbreaks (cholera, measles, dengue, malaria, etc.) in several countries are making it very challenging to implement timely and high-quality polio vaccination campaigns. The committee noted that context-specific tailored interventions will be critical to implement high-quality campaigns and ultimately stop the cVDPV outbreaks in the current complex scenario, with varying challenges in different countries and sub-national geographies. Synchronized sub-regional approaches and strong cross-border coordination will also be critical to jointly address the challenges relating to permeable borders and common operational challenges across countries.

The committee noted some good practices in several countries, particularly on cross-border collaboration and surveillance, and on community and professional engagement. The committee encourages the countries to document and share the best practices and suggests that GPEI facilitates that.

The Committee noted the importance of maintaining sensitive surveillance in the polio infected and high-risk countries and that the GPEI should provide all possible support in this regard under the Global Polio Surveillance Action Plan. The developed countries should also maintain quality surveillance for polioviruses, considering the ongoing importation risk recently highlighted by cVDPV detection in Spain and French Guiana. High-quality surveillance is fundamental to ensure early detection and timely response to importations and newly emerged outbreaks.

The committee noted that novel OPV2 continues to demonstrate high genetic stability compared to Sabin OPV2. However, the risk of new cVDPV2 emergences will remain in the event of long intervals (> 4 weeks) between outbreak response campaigns and low vaccination quality.

The Committee noted that the amendments to the International Health Regulations (2005) (IHR) through resolution WHA77.17 (2024), were notified to States Parties on 19 September 2024 and that they would come into effect on 19 September 2025 for 192 States Parties. Regarding any potential effects of these amendments on the Committee, the Secretariat informed that it would be premature to assess any such effects at this time but would brief the Committee ahead of their entry into force in September 2025.

Based on the current situation regarding WPV1 and cVDPVs, and the reports provided by affected countries, the Director-General accepted the Committee's assessment, and on 3 December 2024 determined that the poliovirus situation continues to constitute a Public Health Emergency of International Concern (PHEIC) with respect to WPV1 and cVDPV. The Director-General endorsed the Committee's recommendations for countries meeting the definition for 'States infected with WPV1, cVDPV1 or cVDPV3 with potential risk for international spread', 'States infected with cVDPV2 with potential risk for international spread' and for 'States no longer infected by WPV1 or cVDPV, but which remain vulnerable to re-infection by WPV or cVDPV' and extended the Temporary Recommendations under the IHR to reduce the risk of the international spread of poliovirus, effective, 3 December 2024.