Polio IHR Emergency Committee Issues 39th Meeting Statement

The thirty-ninth 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 08 July 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 2026 and interruption and certification of cVDPV2 elimination by 2028. Technical updates were received about the situation in the following countries: Afghanistan, Ethiopia, Equatorial Guinea, Kenya, Mali, Niger, Pakistan, Senegal, and Somalia.

Wild poliovirus

Since the last Emergency Committee meeting, twelve new WPV1 cases were reported, five from Afghanistan and seven from Pakistan bringing the total to 14 in 2024. The number of WPV1 positive environmental samples in Pakistan in 2024 is 186 compared to 126 during all of 2023. The number of WPV1 positive environmental samples in Afghanistan in 2024 is 44 compared to 62 in all of 2023.

There has been an upward trend of WPV1 detection in Pakistan since mid-2023, mainly in the environmental samples from Khyber Pakhtunkhwa, Sindh and Balochistan provinces. In Afghanistan, there is increased WPV1 detection in the environmental samples in the South Region since late 2023, in addition to reporting of two WPV1 cases. The committee noted the conclusion of recently held meeting of the Technical Advisory Group (TAG) on polio eradication in Afghanistan and Pakistan that despite overall progress, endemic transmission has been re-established in the historic reservoirs of Kandahar (Afghanistan) and Peshawar (Pakistan) and there is risk of its re-establishment in Karachi and Quetta Block 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 (KP) province of Pakistan. However, there has been persistent transmission of YB3A genetic cluster since May 2022, resulting into 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 and two sub-national vaccination campaigns during the first half of 2024. During the June 2024 nation-wide vaccination campaign, Afghanistan for the first time after more than five years, utilized house-to-house vaccination strategy in the South Region with exception of the Kandahar province, which is a very encouraging development. The campaign quality in the endemic East Region of Afghanistan has reportedly been high in 2024. Nationally, 95% of the target children (aged

There has been no transmission of WPV1 in the African Region in 2024. Following an independent Outbreak Response Assessment (OBRA) in Malawi and Mozambique, the WPV1 outbreak in the African Region has been declared closed as of May 2024.

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 within the two countries in 2023 and 2024.

Circulating vaccine derived poliovirus (cVDPV)

In 2024, there have been 72 cases confirmed with cVDPV, of which 68 are cVDPV2 and four are cVDPV1. Of the 72 cases in 2024, 30 (42%) have occurred in Nigeria. Algeria, Cote d'Ivoire, Egypt, Equatorial Guinea, Gambia, Liberia, Mozambique, Senegal, Sierra Leone, Sudan, Uganda, and Zimbabwe have detected cVDPV in the environment but have not detected any cases.

A total of 527 cases have been confirmed with cVDPV in all of 2023, of which 393 are cVDPV2 and 134 are cVDPV1. Of the 527 cVDPV cases reported in 2023, 224 (43%) have occurred in the DR Congo.

There are two newly infected countries reporting cVDPV2 since the last meeting: Ethiopia and Equatorial Guinea. Both Ethiopia and Equatorial Guinea experienced importations, from South Sudan and Chad respectively. In 2024, the number of circulating cVDPV2 emergence groups detected to date is 13, compared to 27 in 2023, 22 in 2022, 29 in 2021, 36 in 2020, and 44 in 2019. Of the 13 emergence groups circulating in 2024, two are a newly detected this year, both derived from the novel OPV2 vaccine. There have now been 17 nOPV2 derived cVDPV2 emergences since 2021.

All the four cVDPV1 cases in 2024 have been reported from DR Congo. In 2023, a total of 134 cVDPV1 cases were reported including 106 from DR Congo, 24 from Madagascar, and four from Mozambique. Last cVDPV1 detection from Madagascar was in September 2023 and from Mozambique in November 2023.

The committee noted that in the African Region, which now, exclusively uses novel OPV2 for outbreak response, there has been a total of 16 new cVDPV2 emergences detected that have emerged from novel OPV2 use, while there has been one such emergence identified in Egypt in the Eastern Mediterranean Region. 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 and population displacement. These factors are most evident in northern Yemen, northern Nigeria, south-central Somalia and eastern DR Congo.

Conclusion

The Committee unanimously agreed that the risk of international spread of poliovirus still 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, the risk of international spread of WPV1 remains:

• Spread of WPV1 transmission back into formerly endemic areas and core reservoirs of Afghanistan (Kandahar) and Pakistan (Karachi, Peshawar, Quetta Block), that represents a significant risk to the gains made during the last two years.
• The WPV1 transmission has essentially re-established in Kandahar (Afghanistan) and Peshawar (Pakistan).
• This epidemiological context is particularly concerning at the outset of high transmission season in both endemic countries.
• Despite overall resumption of house-to-house vaccination campaigns in Southern Afghanistan, Kandahar province continues to implement site-to-site or mosque-to-mosque campaigns, which has been shown to be less effective than the house-to-house strategy;
• 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
• High-risk mobile populations in Pakistan represent a specific risk of international spread to Afghanistan in particular, compounded by ongoing significant movement the returnees from Pakistan into a number of provinces of Afghanistan;
• Any setback in Afghanistan poses a risk to the programme in Pakistan due to high population movement.

Ongoing risk of cVDPV international spread:

Based on the following factors, the risk of international spread of cVDPV2 appears to remain high although numbers of cVDPV1 cases have gone down:

• Ongoing cross border spread including into newly re-infected countries such as Ethiopia and Equatorial Guinea
• Continued cVDPV2 transmission in the critical areas of Nigeria, with more than 40% of the global cVDPV2 cases in 2024 and it's potential to amplify the transmission
• The cVDPV2 transmission in the Horn of Africa seems to be intensifying during the first half of 2024. The Horn of Africa countries continue to face humanitarian and health emergencies making it very 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
• Despite the decreasing number of cVDPV cases, the transmission continues to be detected in DR Congo, as recent as April 2024 for cVDPV1 and March 2024 for cVDPV2
• The ever-widening gap in population intestinal mucosal immunity in young children since the withdrawal of OPV2 in 2016 and consequently high concentration of zero dose children in certain areas;
• Insecurity 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

WPV1

cVDPV1

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:

Note: After the meeting of the Emergency Committee, WHO was notified on 16 July 2024, of the detection of circulating vaccine-derived poliovirus type 2 (cVDPV2) in 6 environmental samples from Deir Al Balah (3) and Khan Yunis (3) in Gaza Strip of the Occupied Palestinian Territory (oPt). All the positive environmental samples were collected on 23 June 2024. Efforts are already underway at all levels to mount an outbreak response.

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 to determine if there has been local transmission of the imported cVDPV2.
• Noting the existence of a separate mechanism for responding to type 2 poliovirus infections, consider requesting vaccines from the global novel OPV2 stockpile.
• 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.
• 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 should 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 travelers 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, travelers 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

WPV1

cVDPV

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

Additional considerations

The committee notes the geographic spread of WPV1 in Pakistan and Afghanistan at the outset of high transmission season. Moreover, consequent to persistent transmission in Afghanistan and Pakistan, the YB3A genetic cluster of WPV1 has 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.

The committee appreciates the recent steps taken (June 2024) by the Afghanistan Polio Programme towards resumption of house-to-house campaigns in Southern Afghanistan, and notes with concern that Kandahar Province in the region continues to have a large pool of susceptible children due to inability to implement house-to-house campaigns, yet. The committees notes that the overall women's inclusion in vaccination campaigns remains around 20% in Afghanistan, leading to inadequate access to all children in some areas. The committee is encouraged by the appointment of the Prime Minister's Focal Person for Polio Eradication in Pakistan. The Committee encourages Afghanistan and Pakistan polio programmes to maintain coordination, aiming to rapidly improve the access and quality of vaccination campaigns to be able to reach the Goal-1 of the GPEI strategy.

The committee is encouraged by the closure of WPV1 outbreak in the African Region and appreciates the efforts of National Governments and the GPEI in this regard. It is important to maintain high population immunity through routine immunization to avert the risk of future WPV1 outbreaks in the African Region.

The committee noted the ongoing transmission of cVDPV in the African Region and 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 of the African Region are making it very challenging to implement timely and high-quality polio vaccination campaigns. The committee noted the deteriorating cVDPV epidemiology in the Horn of Africa, with concurrent humanitarian and other health related challenges. The committee noted ongoing substantial role of mobile populations in sustaining the cVDPV transmission across several countries. The committee also 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 encourages the countries to document and share the best practices and suggests that GPEI facilitates that.

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 the ongoing supply related challenges regarding novel OPV2 and is encouraged by the prospects for improvement during the second half of 2024, including possible arrival of a second supplier in the market. The committee considered that securing of vaccine supply was a critical issue and that there should be planning to ensure a more robust vaccine supply beyond admission of a new supplier. While encouraging countries to declare public health emergencies following detection of a new outbreak, such crucial actions need to be supported by the GPEI in ensuring vaccine availability.

The committee noted that 20 countries in the African Region are yet to introduce a second dose of IPV in their Routine Immunization schedules. Moreover, a number cVDPV outbreak affected countries continue to have low IPV1 coverage. It is important to take urgent steps to introduce IPV2 in the Routine Immunization of the remaining countries and improve IPV1 coverage, especially in the outbreak affected countries. The committee is encouraged by the prequalification of the Hexavalent Vaccine and availability of GAVI support for its introduction., starting in 2025. The committee appreciates the GPEI plan on integration and encourages to take all steps to implement that and utilize all possible opportunities to boost population immunity against polio, including the Big Catch up.

The committee noted the ongoing GPEI efforts to maintain sensitive surveillance for polioviruses, and that epidemiological and genetic data indicates need for further quality improvement in the WPV1 endemic countries as well as the cVDPV affected countries. The Committee suggested to fast-track the efforts to improve speed of detection to inform rapid response, with special focus on high-risk geographies and populations

The committee noted the review of the International Health Regulations and that amendments to the Regulations were possible in 2024 but that these have not yet come into effect. The Committee felt it was still too early to discontinue the PHEIC as the risk of exportation of both WPV and cVDPVs remains significant, noting also that there has been geographical spread of WPV1 in the Pakistan and Afghanistan epidemiological block in 2023 and 2024.

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 12 continues to constitute a 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 previously infected by WPV1 or cVDPV within the last 24 months' and extended the Temporary Recommendations under the IHR to reduce the risk of the international spread of poliovirus, effective, 12 August 2024.