Statement of the Thirty-first Polio IHR Emergency Committee - World Health Organization

The thirty-first 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 28 February 2022 with committee members and advisers attending via video conference, supported by the WHO Secretariat. The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPV). Technical updates were received about the situation in the following State Parties: Afghanistan, Djibouti, Democratic Republic of the Congo (DR Congo), Malawi, Mozambique, Nigeria, Pakistan, Somalia and Yemen.

Wild poliovirus

The committee was encouraged that WPV1 transmission has fallen to very low levels, with no new case in Pakistan since January 2021 and only four in Afghanistan in 2021 and one in 2022. Environmental surveillance continues to detect low levels of WPV1 transmission in Pakistan with 7.6% of samples testing positive in 2021 compared to 56% in 2020. In the second half of 2021 the proportion was only 1.5%. So far in 2022 there has been no positive sample; the most recent positive sample was collected 3 December 2021 in southern Khyber Pakhtunkhwa (KP).

The committee was very concerned that for the first time since the PHEIC was declared in 2014, there has been a case of polio due to new international spread from the Afghanistan – Pakistan epidemiological block, with WPV1 confirmed in a three year old child from Lilongwe, capital city of Malawi with onset of paralysis in November 2021. Genomic sequencing indicates the closest matching virus to that found in the case is a virus found in 2019 in Pakistan. Of concern, it is unknown whether transmission has been missed in Africa or Asia. This is the first WPV1 detection in the WHO African Region since 2016, when four cases occurred due to endemic transmission in Nigeria. This long distance international spread of polio, presumably by sea or by air traffic, is the first such spread since the 2013 introduction of WPV1 into Syria and Israel. The committee noted that a strong multi country response is being planned in Malawi and four neighboring countries, including a thorough investigation to try to determine more clearly when and how importation of WPV1 occurred.

The committee was very disturbed by the news that eight front line workers in Afghanistan had been attacked and killed in four different locations. These are the first attacks on polio workers since nationwide campaigns resumed in November last year and underline that major challenges remain in the country including security challenges and the adverse economic situation. Nevertheless it was encouraging that 2.6 million previously unreached children had been vaccinated in the November 2021 polio campaign. Data provided to the committee clearly showed that where house to house polio campaigns are possible the vaccine coverage is far higher.

In Pakistan, much progress has been made but gaining access to certain nomadic tribal groups in south KP where there is ongoing community resistance still poses challenges, including some security issues with reports of attacks on police and soldiers. Some polio campaigns have been of insufficient quality, and a comprehensive plan tailored to the local context has been developed for this area, which aims to overcome these chronic challenges and optimize performance. A dedicated regional hub has been established to facilitate implementation of the plan. Another key challenge are the children still missed in core reservoirs which are being reduced through approaches such as dealing with refusals before the campaign starts and using 'influencers', tracking of vaccinators to identify missed children and areas, performing sweeping activities and health camps. The committee noted that every poliovirus detection is being dealt with urgently, including the cases in Afghanistan.

Circulating vaccine derived poliovirus (cVDPV)

There have been four new countries infected with cVDPV2, Chad, Djibouti, Mozambique and Yemen bringing the total number of cVDPV2 infected countries to 29. Of these 29 cVDPV2 infected countries, 12 appear to have halted transmission with no detection for at least six months. Chad which appeared to have halted transmission for 12 months has had a new importation and is again considered infected. The total number of cVDPV2 cases in 2021 is 614, of which 413 have occurred in Nigeria, which is considerably less than the 1079 cases in 2020. As in all the years following 2016 when OPV2 was withdrawn, the number of cVDPV2 cases globally has been greater than the number of WPV1 cases.

Based on analysis of genetic linkages between viruses, cross border spread continues to occur, with spread from Nigeria into Cameroon, CAR, Chad and Niger and from Yemen into Djibouti and Egypt. Despite the ongoing decline in the number of cases and lineages circulating, the risk of international spread of cVDPV2 remains high.

The committee noted that the roll out of wider use of novel OPV2 continues under EUL. The committee also noted the delays concerning the importance of timely, quality outbreak response with countries avoiding timely response with monovalent OPV2, preferring to wait for novel OPV2 to become available.

Conclusion

Although heartened by the apparent progress particularly in Pakistan, 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 recognizes the concerns regarding the lengthy duration of the polio PHEIC and the importance of exploring alternative IHR measures in the future but concluded that there are still significant risks as exemplified by the importation of virus into Malawi. 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 appears to continue:

• the detection of WPV1 in Malawi, particularly as the route from Pakistan to Africa is currently unknown both in time and place.
• the unpredictable situation in Afghanistan, with looming humanitarian crises including food insecurity and risk of financial collapse disrupting eradication activities;
• the large pool of unvaccinated 'zero dose' children in Afghanistan in formerly inaccessible areas in many provinces which represent a major risk of re-introduction of WPV1 in those communities;
• high-risk mobile populations in Pakistan such as migrants, nomads, displaced populations, particularly Afghan refugees represent a specific risk of international spread.
• the ongoing risk posed by the COVID-19 pandemic which may have unpredictable adverse impacts on polio surveillance and on immunization activities.

Ongoing risk of cVDPV2 international spread::

Based on the following factors, the risk of international spread of cVDPV2 appears to remain high:

• the actual ongoing cross border spread including into newly infected countries;
• the explosive outbreak of cVDPV2 in Nigeria which has caused international spread to neighbouring countries;
• the ever-widening gap in population intestinal mucosal immunity in young children since the withdrawal of OPV2 in 2016;
• the same factors regarding the COVID-19 pandemic as mentioned above;

Other factors include

• Weak routine immunization: Many countries have weak immunization systems that can be further impacted by various humanitarian emergencies including COVID-19, and the number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies poses a growing risk, leaving populations in these fragile states vulnerable to outbreaks of polio.
• Lack of access: Inaccessibility continues to be a major risk, particularly in several countries currently infected with cVDPV, i.e. Nigeria, Niger and Somalia, which all have sizable populations that have been unreached with polio vaccine for prolonged periods.

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 no longer infected by WPV1 or cVDPV, but which remain vulnerable to re-infection by WPV or cVDPV.
   

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 considered vulnerable for a further 12 months. After this period, the country will no longer be subject to Temporary Recommendations, unless the Committee has concerns based on the final report.

TEMPORARY RECOMMENDATIONS

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

WPV1   

Afghanistan	most recent detection 14 January 2022
Malawi	most recent detection 19 November 2021
Pakistan	most recent detection 6 December 2021

cVDPV1

Madagascar	most recent detection 7 January 2022
Yemen	most recent detection 27 March 2021

cVDPV3

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 long-term visitors (i.e. > 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 (i.e. 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 (e.g. road, air, sea).
• Further intensify cross-border 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 cross-border populations. Improved coordination of cross-border 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.
• 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:

1. Afghanistan	most recent detection 9 Jul 2021
2. Benin	most recent detection 25 May 2021
3. Burkina Faso	most recent detection 9 June 2021
4. Cameroon	most recent detection 9 June 2021
5. CAR	most recent detection 3 November 2021
6. Chad	most recent detection 10 November 2021
7. Rep Congo	most recent detection 1 June 2021
8. DR Congo	most recent detection 2 January 2022
9. Djibouti	most recent detection 28 December 2021
10. Egypt	most recent detection 18 November 2021
11. Ethiopia	most recent detection 16 September 2021
12. Gambia	most recent detection 9 September 2021
13. Guinea	most recent detection 3 August 2021
14. Guinea Bissau	most recent detection 26 July 2021
15. Iran (Islamic Republic of)	most recent detection 20 Feb 2021
16. Liberia	most recent detection 28 May 2021
17. Mauritania	most recent detection 3 November 2021
18. Mozambique	most recent detection 10 December 2021
19. Niger	most recent detection 22 November 2021
20. Nigeria	most recent detection 13 January 2022
21. Pakistan	most recent detection 11 August 2021
22. Senegal	most recent detection 9 November 2021
23. Sierra Leone	most recent detection 1 June 2021
24. Somalia	most recent detection 1 January 2022
25. South Sudan	most recent detection 8 April 2021
26. Tajikistan	most recent detection 13 August 2021
27. Uganda	most recent detection 1 June 2021
28. Ukraine	most recent detection 24 December 2021
29. Yemen	most recent detection 29 October 2021

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 mOPV2 stockpile based on the recommendations of the Advisory Group on mOPV2.
• Further intensify efforts to increase IPV immunization coverage, including sharing coverage data.
• Intensify national and international surveillance regional cooperation and cross-border 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:

• Encourage residents and long­-term 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 cross-­border coordination to enhance surveillance for prompt detection of poliovirus, and vaccinate refugees, travelers and cross-­border populations, according to the advice of the Advisory Group.

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 infected by WPV1 or cVDPV, but which remain vulnerable to re-infection by WPV or cVDPV

WPV1

cVDPV

China	most recent detection 25 January 2021
Côte d'Ivoire	most recent detection 23 December 2020
Ghana	most recent detection 17 September 2020
Kenya	most recent detection 13 January 2021
Mali	most recent detection 23 December 2020
Sudan	most recent detection 18 December 2020
Togo	most recent detection 9 July 2020

These countries should:

• Urgently strengthen routine immunization to boost population immunity.
• Enhance surveillance quality, including considering introducing 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 cross-­border 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.
• At the end of 12 months without evidence of reintroduction of WPV1 or new emergence and circulation of cVDPV, provide a report to the Director-General on measures taken to implement the Temporary Recommendations.

Additional considerations

The Committee was very concerned by the importation of WPV1 into Africa and urged Malawi and its neighbors collaborate and coordinate in a timely fashion:

• the investigation of all AFP cases and contacts with appropriate stool samples, and undertake a search for missed cases and polio compatible cases;
• high quality polio campaigns with high coverage and careful post campaign monitoring;
• where appropriate, share the results of epidemiological investigations especially where these involve cross border populations;
• in Malawi, ensure the Temporary Recommendations around vaccination of departing travelers are fully implemented and provide a report at the next committee meeting concerning implementation.
• that surveillance should be enhanced in other countries in the region, particularly if there is significant movement of Malawian citizens into that country.

The committee remains very concerned about the situation in Afghanistan and expressed its condolences to the family, friends and colleagues of the killed polio workers. Security arrangements must be reviewed and improved to prevent any further attacks. Noting the humanitarian crisis still unfolding in the country, the committee urged that polio campaigns be integrated with other public health measures wherever possible, including screening children for malnutrition, vitamin A administration and measles vaccination. The committee also strongly suggests house to house campaigns be implemented wherever feasible as these campaigns have been shown to enhance identification of zero dose and underimmunised children, noting that this modality may require further human and financial resourcing. In Pakistan, there is concern about persistent low grade WPV-1 transmission in the central epidemiological corridor (including South KP and South East Afghanistan) and there is a need to strongly address gaps in surveillance and SIA quality.

The Committee welcomed the further progress achieved with the introduction and delivery of nOPV2 but was concerned to hear of significant delays in outbreak response timelines as countries opted to delay response in order to use nOPV2. Polio outbreaks should continue to be met with an aggressive and timely response with the immediately available type-2 vaccine.

The high case numbers of cVDPV2 in Nigeria present a risk not only to Nigeria but also surrounding countries. The committee noted with concern the high number of zero dose children in Nigeria and the low routine immunization rates. The committee urged Nigeria to continue to strengthen essential immunization and improve the quality of polio campaigns.

The committee noted with concern that in Yemen, children are not being accessed for immunization in the Houthi held areas. The committee encouraged ongoing dialogue with all stakeholders to allow access to immunization for all children throughout the country.

The Committee warned of the ongoing effects of COVID-19 particularly on essential immunization and possible future disruptions of immunization activities, and suggested the polio programme could play a role in expediting delivery of COVID vaccines. The committee noted the ongoing work around the duration of the polio PHEIC, and suggested that any lessons learnt from the COVID-19 PHEIC be made available to the committee.

Based on the current situation regarding WPV1 and cVDPV, and the reports provided by affected countries, the Director-General accepted the Committee's assessment and on 4 March 2022 determined that the situation relating to poliovirus 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 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 4 March 2022.