Sunday, December 22, 2024
The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polio viruses (cVDPV). 
The twenty-sixth meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) on the international spread of poliovirus was convened and opened by the WHO Deputy Director-General on 14 October 2020 with committee members attending via video conference, supported by the WHO Secretariat. Dr Zsuzsana Jakab in opening remarks on behalf of Dr Tedros congratulated all those involved in eliminating wild polioviruses from the WHO African Region despite some very challenging obstacles. The COVID-19 pandemic and the ongoing spread of cVDPV2 were both growing major challenges, which would require strenuous efforts to overcome in order to restart progress toward global polio eradication.
The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polio viruses (cVDPV). The following IHR States Parties provided an update at the video conference or in writing on the current situation in their respective countries: Afghanistan, Chad, Egypt, Guinea, Pakistan, Somalia, South Sudan, Sudan and Yemen.
Wild poliovirus
The higher incidence of global WPV1 cases seen during 2020 continues, with 121 cases reported between 1 January – 5 October 2020 compared to 85 for the same period in 2019, a 42% increase. Last year there were 176 WPV1 cases, the highest number reported since the PHEIC was declared in 2014, when there were 359 cases in nine countries. The lowest number of WPV1 cases was reported in 2017, when only 22 cases were found. No wild polio cases have been detected outside of Pakistan and Afghanistan since the last cases in Nigeria in 2016 four years ago. The number of positive environmental samples has increased 70% to 375 compared to 221 for the same time last year. Since the last meeting, exportation of WPV1 from Pakistan to Afghanistan has been documented.
The Committee noted that based on results from sequencing of WPV1 since the last committee meeting in June, there were further instances of international spread of viruses from Pakistan to Afghanistan. The ongoing frequency of WPV1 international spread between the two countries and the increased vulnerability in other countries where routine immunization and polio prevention activities have both been adversely affected by the COVID-19 pandemic are two major factors that suggest the risk of international spread may be at the highest level since 2014. While border closures and lockdowns may mitigate the risk in the short term while in force, this would be outweighed in the longer term by falling population immunity through disruption of vaccination and the resumption of normal population movements.
On the other hand the certification of the WHO African Region as wild polio free in August 2020 indicated a lessening of the global risk from this previous source.
Vaccine derived poliovirus (VDPV)
The committee was very concerned that the international spread of cVDPV2 continues, causing new outbreaks in Guinea, South Sudan and Sudan, the latter two due to importation of a cVDPV2 lineage that emerged in Chad in 2019. The same virus has also been detected in sewage in Cairo, Egypt but with no evidence of local circulation. The number of cases in 2020 is 409 as at 5 October 2020, already exceeding the 378 cases reported for the whole of 2019. As in all other years after 2016 when OPV2 was withdrawn, the number of cVDPV2 cases has been greater than the number of WPV1 cases in 2020. However, the number of sub-types / lineages detected so far in 2020 is 27, compared to 42 for the whole of 2019, and the number of newly emerged viruses is only seven so far this year, compared to 38 during 2019.
Cross border spread of cVDPV2 is now occurring regularly. Based on analysis by the US CDC of isolates, in the three months from April to June 2020, there has been evidence of exportation of cVDPV2 from:
· Pakistan to Afghanistan
· Côte d’Ivoire to Mali
· Guinea to Mali
· Côte d’Ivoire to Ghana, and Ghana to Côte d’Ivoire
· CAR to Cameroon
· Chad to Sudan and South Sudan
· Ghana to Burkina Faso
COVID-19
The committee heard that nearly all countries (90%) have experienced disruption to health services especially in low and middle income countries, according to a survey of 105 countries conducted March – June 2020. Routine immunization particularly outreach services was the area most frequently reported as disrupted.
The committee was very concerned that most of the current outbreak countries have had to delay immunization responses in recent months, meaning that transmission is likely continuing unchecked. Furthermore, there appear to be significant falls in surveillance indicators in many of the outbreak countries, such as drops in AFP reporting rates, and lesser drops in environmental sampling. Vaccine management and supply has been significantly impacted. More than 60 campaigns in 28 countries have been postponed since late February and early March. Vaccine supplies have been disrupted in many ways, with some quantities already in-country at risk of exceeding their expiry data and therefore unusable. Some suppliers are reaching storage capacity and may well be forced to stop production.
Although the resumption of Supplementary Immunization Activities (SIAs) is now occurring, the waves of the pandemic are expected to fluctuate considerably from country to country and across the WHO Regions, so the program will need to adjust according to the COVID-19 situation for the foreseeable future.
Although in general surveillance processes are continuing, there are clear signs of a significant drop in AFP case reporting, including in endemic countries, some outbreak countries and some other non-infected high risk countries.
The committee noted that GPEI modeling indicated there is a risk of an exponential rise in the number of cVDPV2 infected districts in the African Region, leading to a 200% increase if response SIAs had not resumed. In addition to the risk of WPV1 geographical spread and intensification, cVDPV2 cases could rise exponentially in Pakistan and Afghanistan potentially reaching more the 3,500 cases without a resumption of immunization response. Consequently, both Pakistan and Afghanistan are now implementing large scale mOPV2 campaigns and will continue with tOPV/mOPV2 until controlled. While there has been rapid spread, particularly in Afghanistan, expected exponential rise has been curtailed by the resumption of campaigns in July.
Conclusion
The Committee unanimously agreed that the risk of international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC) and recommended the extension of Temporary Recommendations for a further three months. The Committee recognizes the concerns regarding the lengthy duration of the polio PHEIC, but concludes that the current situation is extraordinary, with clear ongoing and increasing risk of international spread and ongoing need for coordinated international response. The Committee considered the following factors in reaching this conclusion:
Rising risk of WPV1 international spread:
Based on the following factors, the risk of international spread of WPV1 appears to be currently very high:
· increasing transmission in Pakistan and Afghanistan as evidenced by higher case numbers and positive environmental samples;
· greater geographical spread within the endemic countries, particularly Afghanistan;
· the ongoing inaccessibility in many provinces of Afghanistan, leading increasingly to highly susceptible populations which are and will continue to drive higher transmission;
· the drop in population immunity consequent on the pause in polio vaccination necessitated by the COVID-19 pandemic, leading to greater susceptibility to poliovirus importation and outbreaks in high risk countries;
· the complicated context of WPV eradication activities in Afghanistan and Pakistan created by the need to simultaneously respond to cVDPV2 and COVID-19;
· the difficulties in supplying vaccines due to the pandemic (as is being seen in Yemen, for example);
· the possible expiring of vaccines in country and stockpiles caused by delays in polio vaccination activities;
· the results of modelling done by GPEI on the potential consequences for WPV1 of the pause on eradication activities.
Rising risk of cVDPV international spread:
The international spread of cVDPV2 is now established, with three newly infected countries being reported since June 2020. While experience demonstrates the effectiveness of Sabin OPV2 in controlling outbreaks, and changes in the strategy and standard operating procedures for responding to cVDPV2 appear to be succeeding in reducing the risk of new emergences in outbreak zones and neighbouring areas, overall the problem continues to grow, affecting more countries and paralyzing more children.
â— COVID-19: This unprecedented pandemic is likely to continue to substantially negatively impact the polio eradication program and outbreak control efforts. The need to take extra precautions to prevent COVID-19 transmission will probably have an impact on vaccination coverage, and also hamper polio surveillance activities leading to increased risk of missed transmission.
â— Falling PV2 immunity: Global population mucosal immunity to type 2 polioviruses (PV2) continues to fall, as the cohort of children born after OPV2 withdrawal grows, exacerbated by poor coverage with IPV particularly in some of the cVDPV infected countries.
â— Weak routine immunization: Many countries have weak immunization systems that can be further impacted by various humanitarian emergencies including COVID19, 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.
â— Lack of access: Inaccessibility continues to be a major risk, particularly in several countries currently infected with WPV or cVDPV, i.e. Afghanistan, Nigeria, Niger, Somalia and Myanmar, which all have sizable populations that have been unreached with polio vaccine for prolonged periods.
â— Population movement: While border closures may have mitigated the short term risk, conversely the risk once borders begin to be re-opened is likely to be higher.
â— The results of cVDPV2 modelling, done by GPEI in June 2020 which had indicated that there was a risk of an exponential rise in the number of cVDPV2 infected districts in the African Region and in Pakistan and Afghanistan.
â— New cVDPV1 outbreak: The new outbreak of cVDPV1 in Yemen in an area of conflict is a further example of the risks anywhere that conflict can contribute to lower immunization rates and therefore new emergences of other cVDPV.
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:
â— States infected with WPV1, cVDPV1 or cVDPV3, with potential risk of international spread.
â— States infected with cVDPV2, with potential risk of international spread.
â— 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:
â— 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.
â— 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
â— 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 7 Sep 2020)
Pakistan (most recent detection 16 Sep 2020)
cVDPV1
Malaysia (most recent detection 13 March 2020)
Philippines (most recent detection 28 November 2019)
Yemen (most recent detection 5 June 2020)
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.
â— 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.
â— 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.
â— 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.
â— 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).
â— 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.
â— 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.
â— Provide to the Director-General a regular report on the implementation of the Temporary Recommendations on international travel.
States infected with cVDPV2s, with potential or demonstrated risk of international spread
Afghanistan (most recent detection 5 September 2020)
Angola (most recent detection 9 February 2020)
Benin (most recent detection 12 June 2020)
Burkina Faso (most recent detection 11 June 2020)
Cameroon (most recent detection 1 September 2020)
CAR (most recent detection 28 July 2020)
Chad (most recent detection 22 August 2020)
Cote d’Ivoire (most recent detection 20 June 2020)
DR Congo (most recent detection 4 August 2020)
Ethiopia (most recent detection 13 June 2020)
Ghana (most recent detection 16 June 2020)
Guinea (most recent detection 21 July 2020)
Malaysia (most recent detection 13 March 2020)
Mali (most recent detection 23 June 2020)
Niger (most recent detection 25 August 2020)
Nigeria (most recent detection 18 June 2020)
Pakistan (most recent detection 24 September 2020)
Philippines (most recent detection 16 January 2020)
Somalia (most recent detection 29 August 2020)
South Sudan (most recent detection 8 July 2020)
Sudan (most recent detection 18 August 2020)
Togo (most recent detection 3 May 2020)
Zambia (most recent detection 25 November 2019)
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.
â— 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.
◠Encourage residents and longterm visitors to receive a dose of IPV four weeks to 12 months prior to international travel; those undertaking urgent travel (i.e. within four weeks) should be encouraged to receive a dose at least by the time of departure.
â— Ensure that travelers who receive such vaccination have access to an appropriate document to record their polio vaccination status.
â— 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.
â— 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.
â— 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’.
â— 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
Mozambique (most recent cVDPV2 detection 17 December 2018)
PNG (most recent cVDPV1 detection 6 November 2018)
Indonesia (most recent cVDPV1 detection 13 February 2019)
Myanmar (most recent cVDPV1detection 9 August 2019)
China (most recentcVDPV2 detection 18 August 2019)
These countries should:
â— Urgently strengthen routine immunization to boost population immunity.
â— 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.
â— Intensify efforts to ensure vaccination of mobile and crossborder populations, Internally Displaced Persons, refugees and other vulnerable groups.
â— Enhance regional cooperation and cross border coordination to ensure prompt detection of WPV1 and cVDPV, and vaccination of high risk population groups.
â— Maintain these measures with documentation of full application of high quality surveillance and vaccination activities.
â— 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 noted with concern the drop in the number of SIAs due to the problems caused by COVID-19, including preventive SIAs in high risk countries that are done to maintain population immunity in places where routine immunization is weak or disrupted. This indicates a very dangerous situation could arise: not only is there increasing WPV1 in the two potential source countries, but the susceptibility in potential outbreak prone countries could significantly and relatively rapidly increase. Furthermore, importations leading to outbreaks may be detected late due to the pandemic’s effect on surveillance. The committee urges all at-risk countries to pay careful attention to managing these risks, ensuring population immunity for polio is maintained throughout the course of the pandemic whether through SIAs or improvements to routine immunization, and attention is also given to enhancement of surveillance, especially environmental surveillance where it remains limited in some high risk areas.
The committee also noted the risk of vaccine hesitancy could be exacerbated during the pandemic, so that adverse events during the development or future deployment of any COVID-19 vaccine could compound the existing issues around polio vaccines, particularly but not only in Pakistan. Conversely, vaccine issues arising out of novel OPV2 or trivalent OPV2 use could adversely affect any future COVID-19 vaccine deployment. The committee urged countries with particular problems around vaccine hesitancy to make preparations now to avert situations of greater vaccine refusals through education campaigns, activities to counter misinformation and rumors and wherever possible provide incentives to target populations such as multi-antigen campaigns and offering other health and wellbeing services (vitamins, anti-worming medication, soap etc).
The committee commended Egypt for its thorough investigation of the finding in Cairo of the VDPV2 poliovirus genetically closely linked to that which is circulating in Sudan and noted there was no evidence that it was circulating in Egypt. However, given recent experience in other countries where such findings often heralded the beginning of an outbreak, the committee requests Egyptian health authorities to continue to monitor the situation carefully and provide a detailed update to the committee at its next meeting. The committee urged any country that detects importation of a VDPV2 known to be circulating in another country prepare for a rapid response should local circulation be identified.
The committee was also very concerned about the polio program funding gap which is developing in 2021 and beyond and urged countries and donors to maintain funding of polio eradication activities, as the potential for reversal of progress appears high, with many years of work undone easily and swiftly if WPV1 spreads outside the endemic countries. The committee was saddened to learn of several deaths of polio workers due to COVID-19, which serves as a reminder that both the polio PHEIC and the COVID-19 PHEIC are at dangerous crossroads and need equal attention. The Committee recommends that in countries with strong polio programs to intensify efforts to link polio eradication and COVID-19 activities including surveillance to provide greater mutual benefits to both initiatives.
The phased replacement during 2021 of Sabin OPV2 with novel OPV2 is expected to substantially reduce the source of cVDPV2 emergence, transmission and subsequent risk of international spread. Full licensure and pre-qualification of nOPV2 is not expected before 2022; therefore all countries at risk of cVDPV2 outbreak should consider preparing for nOPV2 use under Emergency Use Listing procedure.
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 19 October 2020 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 19 October 2020.
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