The thirtieth 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 3 November 2021 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, China, Guinea Bissau, Mauritania, Nigeria, Pakistan, Senegal and Ukraine.
Wild poliovirus
WPV1 transmission has fallen to low levels, with no new case since January 2021 when two WPV1 cases occurred, one each from Pakistan and Afghanistan, compared to 129 WPV1 cases during the same time period in 2020. From environmental surveillance, the overall proportion of specimens that are positive in Pakistan is 10% compared to 56% in 2020 and there have been only seven positive samples since April 2021, meaning the proportion of positives for the last six months is 2.2%. During last three months, only one environmental sample has tested positive for WPV1 from the 163 assessed samples (from DI Khan in August). September 2021 was the first month since environmental surveillance started in Pakistan in which all of the assessed environmental samples tested negative for WPV1. From the samples processed to date in October, no sample has been found positive. The committee also noted the completion of the surveillance review in Pakistan which found a high likelihood that the current WPV1 detection is valid.
The key challenge in Pakistan remains the ‘persistently missed children’ in the core reservoirs regarding which progress is being made through innovative approaches such as deploying evening vaccination teams, health camps, tracking of missed and not available children after the SIA is completed, dealing with refusals before the campaign starts and using pro-vaccination influencers. The key challenge in Afghanistan remains the cumulative backlog of unvaccinated children due to extended inaccessibility for insecurity reasons, and the current instability and humanitarian situation causing uncertainty about programme implementation. The planned NIDs in November and December using a house to house campaign strategy are a key opportunity to address this large pool of unvaccinated children. Based on the progress achieved to date, the Committee noted the cautious optimism of the polio program and that the coming few months would be critical ones in interrupting polio transmission in the two remaining endemic countries. There is no room for complacency, close monitoring will be required to ensure that each and every child is vaccinated.
Circulating vaccine derived poliovirus (cVDPV)
Since the last meeting, three additional countries have been infected with cVDPV2, bringing the total number of currently cVDPV2 infected countries to 30, in three WHO Regions (African, Eastern Mediterranean and European). The number of cVDPV2 cases in 2021 totals 420, of which 266 have occurred in Nigeria. The three newly infected countries were all the result of international spread of cVDPV2, namely Guinea Bissau, Mauritania and Ukraine. Based on analysis of genetic linkages between viruses, cross border spread remains common with 10 documented importations into 10 countries in the second quarter of 2021. Despite the ongoing decline in the number of cases and lineages circulating, the risk of international spread of cVDPV2 remains high, with experience in Egypt and Iran showing that even countries with high IPV coverage are at risk of established cVDPV2 transmission following importation.
The committee noted that SAGE has endorsed the transition of nOPV2 from initial to wider use under EUL, based on the findings of an independent safety and genetic stability assessment. The committee also noted the pandemic-induced shortage of nOPV2 vaccine and underlined the SAGE recommendation concerning the importance of timely, quality outbreak response with the immediately available type-2 vaccine (mOPV2).
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 but concluded that there are still significant risks despite apparent progress made in the two endemic countries, and that the coming three months would be a critical period to monitor the situation there closely. 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 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 formerly inaccessible areas in many provinces of Afghanistan 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, particularly during the northern hemisphere winter months.
Ongoing risk of cVDPV2 international spread::
Based on the following factors, the risk of international spread of cVDPV2 appears to remain high:
- the actual ten documented instances cross border spread into 10 countries of which three are 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;
- the large population of zero dose children in Afghanistan that appears to be driving transmission there.
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 23 February 2021)
Pakistan (most recent detection 9 August 2021)
cVDPV1
Madagascar (most recent detection 13 September 2021)
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 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:
Afghanistan (most recent detection 9 July 2021)
Benin (most recent detection 14 May 2021)
Burkina Faso (most recent detection 9 June 2021)
Cameroon (most recent detection 8 September 2021)
CAR (most recent detection 29 October 2020)
Chad (most recent detection 28 November 2020)
Rep Congo (most recent detection 14 April 2021)
DR Congo (most recent detection 30 April 2021)
Côte d’Ivoire (most recent detection 23 December 2020)
Egypt (most recent detection 8 June 2021)
Ethiopia (most recent detection 16 July 2021)
Gambia (most recent detection 1 July 2021)
Guinea (most recent detection 10 July 2021)
Guinea Bissau (most recent detection 26 July 2021)
Iran (Islamic Republic of) (most recent detection 20 February 2021)
Kenya (most recent detection 25 January 2021)
Liberia (most recent detection 28 May 2021)
Mali (most recent detection 23 December 2020)
Mauritania (most recent detection 1 September 2021)
Niger (most recent detection 20 July 2021)
Nigeria (most recent detection 12 September 2021)
Pakistan (most recent detection 11 August 2021)
Senegal (most recent detection 14 September 2021)
Sierra Leone (most recent detection 1 June 2021
Somalia (most recent detection 23 May 2021)
South Sudan (most recent detection 10 Apr 2021)
Sudan (most recent detection 18 December 2020)
Tajikistan (most recent detection 13 August 2021)
Uganda (most recent detection 1 June 2021)
Ukraine (most recent detection 7 September 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 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:
- 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, 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
none
cVDPV
Angola (most recent detection 9 February 2020)
China (most recent detection 25 January 2021)
Ghana (most recent detection17 September 2020)
Malaysia (most recent detection 13 March 2020)
Philippines (most recent detection 16 January 2020)
Togo (most recent detection 9 July 2020)
Zambia (most recent cVDPV2 detection 25 November 2019)
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 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.
- 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 concerned by the large cVDPV2 outbreak in Nigeria that has recently spilled into Niger and Cameroon. While noting the impact of COVID-19, the committee was concerned about the poor quality of SIAs conducted to date and routine immunization and urged the country to focus its efforts to address these two factors.
The committee was very concerned about the situation in Senegal where there has been an almost 12 month delay since the initial detection with no outbreak response yet conducted which had resulted in further cross border spread. The committee urged Senegal to declare a national public health emergency as a means of invigorating response efforts and to take proactive steps to expedite its outbreak response.
The committee was concerned by the reports of lengthy stockouts of vaccines including polio vaccine in Guinea Bissau and urged the country to take steps to rectify this and avoid repeat occurrences in the future. The committee recommended that routine immunization be reviewed as stockouts may be a symptom of a wider problem.
In Ukraine, steps need to be undertaken quickly to undertake an immunization response using whichever OPV2 is available, in addition to identifying groups and local areas where there are pockets of missed children. The committee noted also the GPEI guidance on polio vaccination in an emergency situation which offers guidance on vaccinating refugees and could be applied to any mobile population.
The committee noted the convincing efforts by China to rule out further transmission and accepted that nine months after the last detection of cVDPV3, China was no longer infected.
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 Committee warned of the ongoing effects of COVID-19 particularly on essential immunization and possible future disruptions of supply and delivery of vaccines. Zero-dose children and communities were missed before the advent of the pandemic and it is critical that these children and communities are prioritized as essential immunization services are restored. COVID-19 is likely to continue to have adverse effects on all health programs and systems for some time to come so the polio programme must continue to manage its response to overcome the remaining hurdles.
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 5 November 2021 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 5 November 2021.