WHO Statement on the international spread of Poliovirus

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Bwari Area Council immunises 140,273 children
Bwari Area Council immunises 140,273 children

Twelfth meeting of the Emergency Committee under the International Health Regulations (2015) regarding the international spread of poliovirus

The twelfth meeting of the Emergency Committee (EC) under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus was convened via teleconference by the Director General on 7 February 2017.

The Emergency Committee reviewed the data on wild poliovirus (WPV1) and circulating vaccine­derived polioviruses (cVDPV). The Secretariat presented a report of progress for affected IHR States Parties subject to Temporary Recommendations. The following IHR States Parties presented an update on the implementation of the WHO Temporary Recommendations since the Committee last met on 11 November 2016: Afghanistan, Pakistan, Nigeria, and Central African Republic. The committee also invited the Russian Federation to provide information about a VDPV event in its territory.

Wild polio

Overall the Committee was encouraged by steady progress in Pakistan and Afghanistan, and was reassured and impressed by the rapid response of the polio eradication programme in Nigeria.

The committee welcomed the dedication in Pakistan to further strengthen surveillance, and in particular the expansion of environmental surveillance to improve detection. The intensity of environmental surveillance is now at unprecedented levels, so that it is likely detections may increase even as transmission in cases is falling. These data need careful interpretation, and the committee acknowledged that this also includes interpretation of data concerning cross-border transmission. The Committee also applauded the information that there were no fully inaccessible children in 2017. However, the recent exportation of WPV1 from Pakistan into Kandahar province of Afghanistan illustrated the difficulty of halting international spread between these two countries.

While the Committee applauded the efforts of Afghanistan to reach inaccessible children and noted the overall reduction in these numbers, the continuing insecurity in parts of Afghanistan means that substantial numbers of children remain inaccessible, heightening anxiety about completion of eradication.

The Committee welcomed the continued emphasis on cooperation along the long international border between the two countries noting that this sub region constitutes an epidemiological block. The committee continues to believe that the international border represents a significant opportunity to vaccinate children who may otherwise have been missed, and welcomed the increase in the number of border vaccination teams. Opportunities to install teams at more informal border crossings should be encouraged.

The Committee commended Nigeria for its rapid response to the WPV1 cases and welcomed that there had been no further cases detected since the last meeting. However, as there remain substantial populations in Northern Nigeria that are totally or partially inaccessible, the committee concluded that it is highly likely that polioviruses are still circulating in these areas. Reaching these populations is critically important for the polio eradication effort, but it is acknowledged that there are significant security risks that may pose danger to polio eradication workers and volunteers. The Committee noted that working under this threat is likely to negatively impact on the quality of the interventions. Nigeria has already adopted innovative and multi-pronged approaches to this problem, and the committee urged that this innovative spirit be continued.

There was ongoing concern about the Lake Chad region, and for all the countries that are affected by the insurgency, with the consequent lack of services, and presence of Internally Displaced Persons (IDPs) and refugees. The risk of international spread from Nigeria to Lake Chad basin countries or further afield in sub-Saharan Africa remains high. The committee was encouraged that the Lake Chad basin countries including Nigeria, Cameroon, Chad, Niger and the Central African Republic (CAR), continued to be committed to sub-regional coordination. CAR needs to maintain the current momentum, including further improvement to AFP surveillance and if feasible introduce environmental surveillance as is currently planned.

Equatorial Guinea remains vulnerable, based on very sub-optimal polio eradication activities including poor surveillance, low routine immunisation coverage, and waning national efforts to address this vulnerability.

Vaccine derived poliovirus

The committee was very concerned that two new outbreaks of cVDPV have been identified, one in Sokoto in northern Nigeria, and the second in Quetta Pakistan. The virus found in Sokoto was unrelated to that found in Borno. Both of these outbreaks highlighted the presence of vulnerable under immunized populations in countries with endemic transmission. The committee noted the response to these outbreaks, acknowledging that in both cases it had complicated the ongoing efforts to eradicate WPV1.

The Committee welcomed the provision of information by the Russian Federation at the meeting about the recent detection of VDPV in two children from the Chechen Republic, and also welcomed the surveillance and immunization activities taken to date in response. The Committee noted that the investigation by the Russian Federation had shown that one of the children was immunosuppressed. The Committee requested that the WHO European Regional office and WHO HQ should continue to work with the Russian Federation to confirm the classification of the viruses. Therefore as the risk of international spread is still being assessed, no recommendations regarding this situation have been made by the committee.

In Guinea, the most recent case of cVDPV had onset in December 2015, and based on the most recent assessments and the criteria of the committee, the country is no longer considered as infected, but remains vulnerable.

The committee also noted the detection of non-circulating VDPV in several other countries.

Conclusion

The Committee unanimously agreed that the international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC), and recommended the extension of the Temporary Recommendations for a further three months. The Committee considered the following factors in reaching this conclusion:

  • The outbreak of WPV1 and cVDPV in Nigeria highlighting that there are high-risk areas where surveillance is compromised by inaccessibility, resulting in ongoing circulation of WPV for several years without detection. The risk of transmission in the Lake Chad sub-region appears high.
  • The continued international spread of WPV1 between Pakistan and Afghanistan.
  • The persistent, wide geographical distribution of positive WPV1 in environmental samples and AFP cases in Pakistan, while acknowledging the intensification of environmental surveillance inevitably increasing detection rates.
  • The current special and extraordinary context of being closer to polio eradication than ever before in history, with the lowest number of WPV1 cases ever recorded occurring in 2016.
  • The risk and consequent costs of failure to eradicate globally one of the world’s most serious vaccine preventable diseases. Even though global transmission has fallen dramatically and with it the likelihood of international spread, the consequences and impact of international spread should it occur would be grave.
  • The possibility of global complacency developing as the numbers of polio cases continues to fall and eradication becomes a possibility.
  • The serious consequences of further international spread for the increasing number of countries in which immunization systems have been weakened or disrupted by conflict and complex emergencies. 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.
  • The continued necessity for a coordinated international response to improve immunization and surveillance for WPV1, to stop international spread and reduce the risk of new spread.
  • The importance of a regional approach and strong cross­border cooperation, as much international spread of polio occurs over land borders, while also recognizing that the risk of distant international spread remains from zones with active poliovirus transmission.
  • Additionally with respect to cVDPV:
    • cVDPVs also pose a risk for international spread, which without an urgent response with appropriate measures threatens vulnerable populations as noted above;
    • The ongoing circulation of cVDPV2 in Nigeria and Pakistan, demonstrates significant gaps in population immunity at a critical time in the polio endgame;
    • The ongoing urgency to prevent type 2 cVDPVs following the globally synchronized withdrawal of the type 2 component of the oral poliovirus vaccine in April 2016;
    • The ongoing challenges of improving routine immunization in areas affected by insecurity and other emergencies, including the post Ebola context;
    • The global shortage of IPV which poses an additional threat from cVDPVs.

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:

Wild poliovirus

  • States currently exporting WPV1;
  • States infected with WPV1 but not currently exporting;
  • States no longer infected by WPV1, but which remain vulnerable to international spread.

Circulating vaccine derived poliovirus

  • States currently exporting cVDPV;
  • States infected with cVDPV but not currently exporting;
  • States no longer infected by cVDPV, but which remain vulnerable to the emergence and circulation of VDPV.

The Committee applied the following criteria to assess the period for detection of no new exportations and the period for detection of no new cases or environmental isolates of WPV1 or cVDPV:

Criteria to assess States no longer exporting (detection of no new WPV1 or cVDPV exportation)

  • Poliovirus Case: 12 months after the onset date of the first case caused by the most recent exportation 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 the first case caused by the most recent importation have been tested for polio and excluded for newly imported WPV1 or cVDPV, and environmental samples collected within 12 months of the first case have also tested negative, whichever is the longer.
  • Environmental isolation of exported poliovirus: 12 months after collection of the first positive environmental sample in the country that received the new exportation PLUS one month to account for the laboratory testing and reporting period.

Criteria to assess States no longer infected (detection of no new 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 samples collected within 12 months of the last case have also tested negative, whichever is the longer.
  • Environmental isolation of WPV1 or cVDPV (no poliovirus case): 12 months after collection of the most recent positive environmental sample PLUS one month to account for the laboratory testing and reporting period.

Temporary recommendations

States currently exporting WPV1 or cVDPV

Currently Pakistan – last WPV1 exportation: 13 January 2017, to Afghanistan; last case 22 December 2016.

Exporting 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; where such declaration has already been made, this emergency status should be maintained.
  • Ensure that all residents and long­term visitors (i.e. > four weeks) of all ages, receive a dose of oral poliovirus vaccine (OPV) 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 OPV 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 travellers.
  • Ensure that such travellers 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 travellers from all points of departure, irrespective of the means of conveyance (e.g. road, air, sea).
  • Recognizing that the movement of people across the border between Pakistan and Afghanistan continues to facilitate exportation of WPV1, both countries should further intensify cross­border efforts by significantly improving coordination at the national, regional and local levels to substantially increase vaccination coverage of travellers crossing the border and of high risk cross­border populations. Both countries have maintained permanent vaccination teams at the main border crossings for many years. 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 travellers that are identified as unvaccinated after they have crossed the border.
  • Maintain these measures until the following criteria have been met: (i) at least six months have passed without new exportations 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 criteria of a ‘state no longer exporting’.
  • Provide to the Director General a monthly report on the implementation of the Temporary Recommendations on international travel, including the number of residents whose travel was restricted and the number of travellers who were vaccinated and provided appropriate documentation at the point of departure.

States infected with WPV1 or cVDPVs but not currently exporting

Infected countries (WPV1)
  • Nigeria (last case 21 Aug 2016)
  • Afghanistan (last case 13 Jan 2017)
Infected countries (cVDPV)
  • Nigeria (last case 28 Oct 2016)
  • Pakistan (last case 17 Dec 2016)
  • Lao People’s Democratic Republic (last case 11 Jan 2016)

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; where such declaration has already been made, this emergency status should be maintained.
  • Encourage residents and long­term visitors to receive a dose of OPV or 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.
  • Ensure that travellers 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 substantially increase vaccination coverage among refugees, travellers and cross­border populations.
  • Maintain these measures until the following criteria have been met: (i) at least six months have passed without the detection of WPV1 transmission or circulation of VDPV 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 international spread, and states that are vulnerable to the emergence and circulation of VDPV

WPV1
  • Cameroon (last case 9 Jul 2014)
  • Niger (last case 15 Nov 2012)
  • Chad (last case 14 Jun 2012)
  • Equatorial Guinea (last case 13 May 2014)
  • Central African Republic (last case 8 Dec 2011)
cVDPV
  • Ukraine (last case 7th July 2015)
  • Madagascar (last case 22nd August 2015)
  • Myanmar (last case 5th October 2015)
  • Guinea (last case 14th December 2015)

These countries should:

  • Urgently strengthen routine immunization to boost population immunity.
  • Enhance surveillance quality 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 (1) 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 for all infected and high risk countries

The Committee strongly urged global partners in polio eradication to provide optimal support to all infected and vulnerable countries at this critical time in the polio eradication programme for implementation of the Temporary Recommendations under the IHR, as well as providing ongoing support to all countries that were previously subject to Temporary Recommendations (Somalia, Ethiopia, Syria, Iraq and Israel).

The committee requested the secretariat to provide data on routine immunization in countries subject to Temporary Recommendations. Recognizing that cVDPV illustrates serious gaps in routine immunization programmes in otherwise polio free countries, the Committee recommended that the international partners in routine immunization, for example Gavi, should assist affected countries to improve the national immunization programme.

The Committee noted the Secretariat’s report on the identification of Sabin 2 virus detected in environmental samples in several countries, and in some of these cases probably due to the ongoing use of tOPV in the private sector. The Committee requested a full report on this at the next meeting.

The Committee noted a more detailed analysis of the public health benefits and costs of implementing temporary recommendations was completed and warranted further discussion and review.

The Committee urged all countries to avoid complacency which could easily lead to a polio resurgence. Surveillance particularly needs careful attention to quickly detect any resurgent transmission.

Based on the advice concerning WPV1 and cVDPV, and the reports made by Afghanistan, Pakistan, Nigeria, and the Central African Republic, the Director General accepted the Committee’s assessment and on 13 February 2017 determined that the events relating to poliovirus continue to constitute a PHEIC, with respect to WPV1 and cVDPV. The Director General endorsed the Committee’s recommendations for countries falling into the definition of ‘States currently exporting WPV1 or cVDPV’, for ‘States infected with WPV1 or cVDPV but not currently exporting’ and for ‘States no longer infected by WPV1, but which remain vulnerable to international spread, and states that are vulnerable to the emergence and circulation of VDPV’ and extended the Temporary Recommendations as revised by the Committee under the IHR to reduce the international spread of poliovirus, effective 13 February 2017.

The Director General thanked the Committee Members and Advisors for their advice and requested their reassessment of this situation within the next three months.

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