The thirty-second 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 15 June 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) in the context of global eradication of WPV and cessation of outbreaks of cVDPV2 by end of 2023. Technical updates were received about the situation in the following countries and territories: Afghanistan, Democratic Republic of the Congo, Israel, Malawi, the occupied Palestinian territory and Pakistan, and written updates were provided by Eritrea and Yemen.

Wild poliovirus

The committee was very concerned that a second WPV1 had been detected in south-eastern Africa, in Mozambique, close to the border with Malawi where the first case was detected. Furthermore, genetic sequencing analysis of the two wild polioviruses indicates a single importation event from Pakistan / Afghanistan into southeastern Africa; the importation event is estimated to have occurred between July 2019 (date of the common node between Pakistan viruses and Malawi/Mozambique viruses) and December 2020 (date of the common node between Malawi and Mozambique viruses). COVID19-related severe movement restrictions implemented in March 2020 in Pakistan and Afghanistan means it is less likely exportation could have occurred between March and December 2020. The Malawi and Mozambique viruses independently evolved for about 0.9 and 1.2 years respectively until first detected and are both considered orphan viruses, and the absence of detection of circulating WPV1 viruses in Malawi and Mozambique between 2019 and 2021 suggests surveillance gaps in southeastern Africa. The original WPV1 cluster in south Asia has not been detected there since December 2020.

The committee noted that the certification of polio eradication African Region was not affected by the outbreak, as it is due to importation rather then endemic transmission. The committee also noted the importance of cross border activities in the outbreak response.

A multi-country response to the WPV1 outbreak is continuing, with four immunization rounds being conducted in Malawi, Mozambique, Tanzania, Zambia; Zimbabwe will join the response for rounds 3 and 4. Additionally, retrospective case searching, surveillance strengthening and improving essential immunization are all ongoing. The committee noted that while administrative coverage was high, problems with population data made these coverage estimates unreliable. Monitoring coverage by Lot Quality Assurance Sampling (LQAS) showed far lower coverage, and the committee noted that countries that have long been polio free needed assistance from GPEI partners in the implementation of supplementary immunization activities (SIAs).

The committee was concerned about the recent outbreak of WPV1 in the North Waziristan district of southern Khyber Pakhtunkhwa (KP) province in Pakistan. Since the last Emergency Committee (EC) meeting in February 2022, Pakistan has reported ten WPV1 cases from North Waziristan and two WPV1 positive environmental samples from the neighboring district of Bannu. With the ongoing WPV1 circulation in South KP, the risks to the rest of Pakistan has escalated.

The key challenges which hampered progress in southern KP include the complex security situation, specifically in North and South Waziristan, which resulted in inadequate access, missed children and reduced quality of SIAs. Community resistance with refusals to vaccination (including vaccination boycotts and fake finger-marking without vaccination), lack of female frontline workers and high turnover of frontline workers, and weak health infrastructure and service delivery all pose challenges. The ten WPV1 cases reported in 2022 are zero dose for routine immunization, zero dose or under-immunized in SIAs, and are from refusal families.

Another challenge in South KP is the sub-optimal Routine Immunization (RI) and progress on strengthening RI in South KP is slow.

The committee commended the dedication of frontline health workers who continue to seek every child who needed vaccination and extended its sympathy to the families of the 17 health workers who were killed in February 2022 in Takhar and Kunduz in Afghanistan. It is encouraging that 2.6 million previously unreached children have been vaccinated, and the number of children not yet accessed by immunization teams was down to an estimated 700,000. Data provided to the committee clearly showed that where house to house polio campaigns are possible the vaccine coverage is far higher.

There has been continuous / steady progress in the rest of Pakistan with no WPV1 detection in last 11 months. Last WPV1 case and positive environmental sample outside of South KP were detected in January 2021 and July 2021 respectively.

Circulating vaccine derived poliovirus (cVDPV)

Eritrea has reported detection of cVDPV2 for the first time, and the virus is most closely linked to a virus found in Sudan in 2020, indicating that both new international spread and missed transmission has occurred. Furthermore, the detection of cVDPV2 in Ghana, Togo and Côte d’Ivoire appears to have resulted from new spread from Nigeria. A new outbreak of cVDPV3 has been detected in Israel in a population sub-group who refuse vaccination. Environmental detection has also occurred in sites in the occupied Palestinian territory. High levels of transmission of cVDPV2 are occurring in northern Yemen, northern Nigeria, and eastern DR Congo, which have reported 115 out of 127 cases to date in 2022. Because of the conflict, no immunization rounds have been conducted in northern Yemen.

Despite the ongoing decline in the number of cases and lineages circulating, the risk of international spread of cVDPV2 remains high as evidenced by recent spread from Nigeria to West Africa. The large amount of transmission occurring in Nigeria along with chronically low immunization coverage is now resulting in spread to multiple countries, while the detection of cVDPV2 in Eritrea of an orphan virus means that missed transmission has occurred in the Horn of Africa also. The persistence of cVDPV2 in Somalia is another concern. The successful introduction of novel OPV2 and re-introduction of tOPV are expected to mitigate the risk of international spread of cVDPV2, particularly as supply issues are resolved in the second half of 2022.

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 or trivalent OPV, preferring to wait for novel OPV2 to become available. The committee noted that SAGE recommends that speed in the rollout of any of these three vaccines is of paramount importance and countries should avoid delays associated with waiting for novel OPV2.

The committee noted that the outbreak in Israel again shows that even countries with high immunization coverage can have pockets of high risk children which can sustain an outbreak.

Conclusion

Although heartened by the apparent progress, 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 and Mozambique. 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:

the current outbreak of WPV1 in Pakistan where there have been 10 cases in just the last three month which must be contained;

high-risk mobile populations in Pakistan such as migrants, nomads, displaced populations, particularly Afghan refugees represent a specific risk of international spread.

the unpredictable situation in Afghanistan, with ongoing and deteriorating humanitarian crises including food insecurity and risk of financial collapse disrupting eradication activities;

the detection of WPV1 in Malawi and Mozambique, particularly as the route from Pakistan to Africa remains unknown;

the sub-optimal immunization coverage obtained through recent rounds in southeastern Africa, meaning ongoing transmission could be occurring;

complacency leading to inadequate surveillance means that such transmission could be missed;

the large pool of unvaccinated ‘zero dose’ children in Afghanistan in formerly inaccessible areas in many provinces, while decreasing, still represent a major risk of re-introduction of WPV1 in those communities;

although COVID-19 cases are currently at low levels in Afghanistan and Pakistan, further waves of cases are possible, 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 northern Yemen, and ongoing high transmission in eastern Democratic Republic of the Congo and northern Nigeria, which have caused international spread to neighbouring countries;

the lack of timely high quality responses in many countries;

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, especially the four areas mentioned above (second dot point)

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:

States infected with WPV1, cVDPV1 or cVDPV3.

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

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 4 May 2022

Malawi: most recent detection 19 November 2021

Mozambique: most recent detection 25 March 2022

Pakistan: most recent detection 15 May 2022

cVDPV1

Madagascar: most recent detection 9 May 2022

cVDPV3

Israel: most recent detection 24 March 2022

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 (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 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.

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 9 September 2021

3. Burkina Faso: most recent detection 9 June 2021

4. Cameroon: most recent detection 29 October 2021

5. CAR: most recent detection 4 May 2022

6. Chad: most recent detection 25 March 2022

7. Côte d’Ivoire: most recent detection 9 February 2022

8. DR Congo: most recent detection 7 April 2022

9. Djibouti: most recent detection 27 March 2022

10. Egypt: most recent detection 28 April 2021

11. Eritrea: most recent detection 3 September 2021

12. Ethiopia: most recent detection 16 September 2021

13. Gambia: most recent detection 9 September 2021

14. Ghana: most recent detection 17 May 2022

15. Guinea: most recent detection 3 August 2021

16. Guinea Bissau: most recent detection 26 July 2021

17. Liberia: most recent detection 28 May 2021

18. Mauritania: most recent detection 3 November 2021

19. Mozambique: most recent detection 26 March 2022

20. Niger: most recent detection 18 April 2022

21. Nigeria: most recent detection 16 April 2022

22. Pakistan: most recent detection 11 August 2021

23. Senegal: most recent detection 18 November 2021

24. Sierra: Leone most recent detection 1 June 2021

25. Somalia: most recent detection 10 March 2022

26. South Sudan: most recent detection 8 April 2021

27. Togo: most recent detection 22 March 2022

28. Uganda: most recent detection 2 November 2021

29. Ukraine: most recent detection 24 December 2021

30. Yemen: most recent detection 3 March 2022

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

Congo: most recent detection 1 June 2021

Iran (Islamic Republic of): most recent detection 20 February 2021

Kenya: most recent detection 13 January 2021

Mali: most recent detection 23 December 2020

Sudan: most recent detection 18 December 2020

South Sudan: most recent detection 18 April 2021

Tajikistan: most recent detection 13 August 2021

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 the low quality campaigns so far and urged GPEI to provide urgent support to the countries involved in the response, Malawi, Mozambique, Tanzania, Zambia and Zimbabwe. These countries need to collaborate and coordinate in a timely fashion to achieve the following:

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 and Mozambique, ensure the Temporary Recommendations around vaccination of departing travelers are fully implemented and provide a report at the next committee meeting concerning implementation; and

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 under-immunized children. , noting that this modality may require further human and financial resourcing. In Pakistan, there is concern about persistent low grade WPV1 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 as recommended by SAGE.

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 WPV1 outbreak in southeastern Africa serves as a reminder to all countries of the risk of missed importation and subsequent spread. All countries need to review their surveillance systems to identify high risk populations with accumulation of zero dose children, particularly where recovery of surveillance following the COVID-19 pandemic has been only partial. Countries also need to take greater ownership of polio prevention and surveillance, especially as donor funding is diverted to COVID-19 needs and other emerging public health issues such as monkeypox, and other global issues such as the war in Ukraine. Countries and international partners need to make clear messaging about the importance of vaccination in the face of ‘vaccine fatigue’ and skepticism in many communities.

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. Stopping transmission in Somalia and Yemen is one of the main challenges in meeting the global goal of stopping outbreaks of cVDPV2 by end of 2023.

The Committee warned of the ongoing effects of COVID-19 particularly on essential immunization and surveillance with possible future disruptions of polio programme activities.

The committee noted the ongoing work around the duration of the polio PHEIC, and possible amendments to the IHR, and suggested that the committee be kept informed of the process.

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 20 June 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 20 June 2022.

Source: World Health Organization