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.
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.
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:
Ongoing risk of cVDPV2 international spread::
Based on the following factors, the risk of international spread of cVDPV2 appears to remain high:
Other factors include
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:
Criteria to assess States as no longer infected by WPV1 or cVDPV:
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
cVDPV1
cVDPV3
These countries should:
States infected with cVDPV2, with or without evidence of local transmission:
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
States with local transmission of cVDPV2, with risk of international spread should in addition to the above measures:
For both sub-categories:
States no longer infected by WPV1 or cVDPV, but which remain vulnerable to re-infection by WPV or cVDPV
WPV1
cVDPV
These countries should:
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 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.
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