IHR Emergency Committee Issues Statement on the International Spread of Poliovirus

The 18th meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus was convened by the director-general on Aug. 15, 2018 at World Health Organization (WHO) headquarters with members, advisers and invited member states attending via teleconference.

The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine derived polioviruses (cVDPV). The Secretariat presented a report of progress for affected IHR States Parties subject to Temporary Recommendations. The following IHR States Parties provided an update on the current situation and the implementation of the WHO Temporary Recommendations since the Committee last met on April 30, 2018: Afghanistan, Democratic Republic of the Congo (DR Congo), Nigeria, Pakistan, Papua New Guinea (PNG), and Somalia.

Wild polio
Overall the Committee was encouraged by continued progress in WPV1 eradication, with the number of cases globally remaining low in 2018, but was concerned about the increase number of WPV cases in Afghanistan. In addition, there has been no international spread of WPV1 since October 2017.

The Committee commended the continued high level commitment seen in both Afghanistan and Pakistan, and the significant degree of cooperation and coordination, particularly in reaching high risk mobile populations that frequently cross the international border. The joint planning to cease transmission in the two recognized zones of transmission (the northern corridor which extends from Nangarhar to Islamabad and Rawalpindi, and the southern corridor from Kandahar to Quetta Block) is a key to success in achieving WPV eradication in Pakistan and Afghanistan, the Region, and globally. The committee noted that it is four years since there has been international spread outside of these two epidemiologically linked countries.

The Committee commended the achievements in Pakistan that have resulted in a sustained reduction in the number of cases, with only three cases so far in 2018 from one district, and a fall in the proportion of environmental samples that have tested positive for WPV1. However, environmental surveillance continues to detect WPV1 transmission in many high-risk areas of the country such as Karachi, Peshawar and the Quetta Block. The drive to finish eradication in the 2018-19 polio low transmission season and the steps taken to ensure maintenance of current efforts during the political transition in Pakistan were also welcomed.

The Committee was very concerned by the increase in WPV1 cases in Afghanistan in 2018, with 11 cases reported so far, compared to six at the same time last year. The increased insecurity resulting in nearly 1 million being inaccessible in recent polio immunization campaigns was a significant part of the reason for the jump in cases, along with persisting pockets of missed children, particularly in the southern and eastern regions

The Committee commended the strong efforts to reach inaccessible and trapped children in Borno, Nigeria, even in the face of increased insecurity, and noted that 15,606 settlements have been reached at least once by vaccination teams as at May 2018, with 3218 remaining unreached. Furthermore, use of community monitors from inaccessible settlements has expanded surveillance reach and resulted in the notification of AFP cases from Abadam and Marte that were silent for the last two years (before 2018). It is now two years since the last WPV1 was detected in Nigeria, and four years since there has been any international spread.

There is ongoing concern about the districts of the neighboring countries of the Lake Chad basin region that have been affected by the Boko Haram insurgency, with the consequent lack of services and presence of IDPs and refugees. The risk of international spread from Nigeria to the Lake Chad basin countries or further afield in sub-Saharan Africa remains substantial. The Committee was encouraged that the Lake Chad basin countries, Cameroon, Chad, the Central African Republic (CAR), Niger and Nigeria continued to be committed to sub-regional coordination of immunization and surveillance activities. However, there are widespread persistent gaps in population immunity across these countries, and the ongoing population movement in the sub-region and insecurity are major challenges.

Vaccine derived poliovirus
The committee was very concerned by the increase in circulating vaccine derived polioviruses (cVDPV). Since the last meeting, new emergences with circulation of VDPV have been detected in Papua New Guinea, DR Congo (Mongala) and Nigeria (Sokoto). In Nigeria and DR Congo multiple lineages of cVDPV2 are circulating concurrently, and in Somalia, both cVDPV2 and cVDPV3 are circulating.

Control of the outbreaks in DR Congo remains difficult to achieve. Gene sequencing and analysis has shown that there have been three different cVDPV2 sub-types circulating. The analysis of the newly detected cVDPV2 in Mongala Province indicates the virus has emerged after OPV2 withdrawal in 2016. Conflict and population movement within and outside DR Congo represent a risk of further spread. The detection of cVDPV2 in Ituri Province far from previously detected cases and adjacent to the border with Uganda heightened these concerns and is an example that the virus can spread long distances. The outbreaks of Ebola virus disease further complicates the response.

The new outbreak of cVDPV1 in PNG highlights that there are vulnerable areas of the world not usually the focus of eradication efforts. The swift action of the Government of PNG in declaring a national public health emergency was welcomed, and highlights the utility of the Temporary Recommendations in such circumstances.

The outbreaks of cVDPV2 in Somalia and Kenya, and cVDPV3 in Somalia are of major concern, particularly the apparent international spread between Somalia and Kenya.

The outbreaks of cVDPV2 in Jigawa, and for the second time in Sokoto, Nigeria, again underlines the vulnerability of northern Nigeria to poliovirus transmission. Routine immunization coverage remains very poor in many areas of the country, although the national emergency programme to strengthen routine immunisation is beginning to make an impact in some areas.

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 considered the following factors in reaching this conclusion:

- Although the risk of international spread of WPV has greatly diminished since the PHEIC was declared in 2014, should international spread now occur, the impact on progress towards WPV eradication would be even more grave in terms of delaying certification and prolonging requirements for dedicated human and financial resources in support of the eradication effort.
- There is a risk of growing global complacency as the numbers of WPV cases remains low and eradication becomes a tangible reality, and removal of the PHEIC now could contribute to greater complacency.The apparent reversal in progress in Afghanistan heightens concerns.
- Many countries remain vulnerable to WPV importation. Gaps in population immunity in several key high-risk areas is evidenced by the current number of cVDPV outbreaks of all serotypes, which only emerge and circulate when polio population immunity is low as a result of deficient routine immunization programs.
- The new international outbreak of cVDPV2 affecting Somalia and Kenya, with a highly diverged cVDPV2 that appears to have circulated undetected for up to four years, highlights that there are still high-risk populations in South and Central zones of Somalia where population immunity and surveillance are compromised by conflict.
- Inaccessibility to vaccination programs remains another major risk, particularly in several countries currently infected with WPV or cVDPV, i.e. Afghanistan, Nigeria and Somalia, which all have sizable populations that have been unreached with polio vaccine for prolonged periods.
- The risk is amplified by population movement, whether for family, social, economic or cultural reasons, or in the context of populations displaced by insecurity and returning refugees. There is a need for international coordination to address these risks, particularly between Afghanistan and Pakistan, Nigeria and its Lake Chad neighbors, and countries in and bordering the Horn of Africa and DR Congo.
- The inaccessible population in Borno state in Nigeria remains substantial despite the commendable efforts to reach all settlements.Some of these populations have not received polio vaccine since WPV1 was detected in 2016, so ongoing transmission in these unreached pockets cannot be ruled out. The risk of transmission in the Lake Chad sub-region appears considerable, with significant gaps in population immunity in these vulnerable countries, compounded by international population movement.
- The difficulty in controlling spread of cVDPV2 in DR Congo demonstrates significant gaps in population immunity at a critical time in the polio endgame;the lack of IPV vaccination in several countries neighboring DR Congo heightens the risk of international spread, as population immunity is rapidly waning.
- The increasing number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies poses another risk. Populations in these fragile states are vulnerable to outbreaks of polio. Outbreaks in fragile states are exceedingly difficult to control and threaten the completion of global polio eradication during its end stage.
- A regional approach and strong cross­border cooperation is required to respond to these risks, as much international spread of polio occurs over land borders.

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, with potential risk of international spread.
- States infected with cVDPV2, with potential risk of international spread.
- 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 (e.g. Borno)
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 5 Aug 2018)

Pakistan (most recent detection 30 July 2018)

Nigeria (most recent detection 27 Sept 2016)

cVDPV1

Papua New Guinea (most recent detection 8 July 2018)

cVDPV3

Somalia (most recent detection 23 May 2018)

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 cVDPV2s, with potential risk of international spread
DR Congo(most recent detection 24 June 2018)
Kenya(most recent detection 21 March 2018)
Nigeria(most recent detection 15 July 2018)
Syrian Arab Republic(most recent detection 21 Sept 2017)
Somalia(most recent detection 10 July 2018)

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.
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 (if available in country) 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.
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.
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 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
Cameroon (last case 9 Jul 2014)
Central African Republic (last case 8 Dec 2011)
Chad (last case 14 Jun 2012)
Niger (last case 15 Nov 2012)

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.
*For the Lake Chad countries, this will be linked to when Nigeria is considered no longer infected by WPV1 or cVDPV2.

Additional considerations

The outbreak in Papua New Guinea again highlights the ongoing vulnerability of some parts of the world to polioviruses. The committee urged countries in close proximity to the current outbreaks, such as Ethiopia, South Sudan and Indonesia to strengthen polio surveillance and routine immunization.

The Committee noted that the extension of the PHEIC for over four years in the context of the end game of the global eradication effort, was an exceptional use of the IHR. The committee noted that some stakeholders are questioning whether this continued declaration of a PHEIC may weaken its impact as a tool to address global health emergencies, and specifically whether it continues to have utility noting that the risk of international spread appears to have substantially diminished since 2014. It noted that it was not originally envisaged that a PHEIC would continue for such a long interval, but the committee feels that the circumstances of an eradication program such as polio are unique. The committee was deeply concerned that the abrupt removal of the PHEIC might send out the wrong message to the global community and might reverse the gains made in reducing the risk of international spread in some areas. There is sound evidence that the Temporary Recommendations have been an important factor in reducing the risk of international spread since 2014 [1][2]. The committee requested the secretariat to review whether there were alternative approaches or tools to achieve the same outcomes as the Temporary Recommendations for the polio PHEIC and report back to the committee in three months.

Based on the current situation regarding WPV1 and cVDPV, and the reports provided by Afghanistan, DR Congo, Nigeria, Pakistan, Papua New Guinea and Somalia, the Director-General accepted the Committee’s assessment and on 27 August 2018 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 Aug. 27, 2018.

[1] Wilder-Smith A, Leong WY, Lopez LF, et al. Potential for international spread of wild poliovirus via travelers. BMC Med 2015; 13: 133.

[2] Duintjer Tebbens RJ, Thompson KM. Modeling the costs and benefits of temporary recommendations for poliovirus exporting countries to vaccinate international travelers. Vaccine 2017; 35(31): 3823-33

Source: WHO