The thirteenth meeting of the Emergency Committee under the International Health Regulations (2005) (IHR) regarding the international spread of poliovirus was convened via teleconference by the Director General on 24 April 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 7 February 2017: Afghanistan, Pakistan, Nigeria, and Equatorial Guinea. The committee also invited the Russian Federation and the Netherlands to provide information about polio events in their respective territories.
Wild polio
Overall the Committee was encouraged by continued steady progress in all three WPV1 infected countries, Pakistan, Afghanistan, and Nigeria, and the fall in the number of cases globally. While falling transmission in these three countries decreased the risk of international spread, the consequences should spread occur would represent a significant set-back to eradication and a risk to public health.
The Committee commended the efforts of Pakistan to further strengthen surveillance, and noted that the intensity of environmental surveillance in the country is now at unprecedented levels in the history of the polio eradication program. However, the recent orphan virus detected in Punjab province highlighted there are still gaps in surveillance. The Committee applauded the information that there were no fully inaccessible children in 2017, and the steady progress in the quality of supplementary immunization activities (SIA).
The Committee welcomed the reduction in Afghanistan in the number of inaccessible children and particularly the progress in reaching high-risk populations in Kunduz. However, the recent international spread of WPV1 from Pakistan into Kandahar, Hilmand and Kunduz provinces of Afghanistan illustrated that population movement between these two countries is an ongoing challenge to achieving eradication, and that gaps in population immunity continued despite improving SIA quality.
The Committee was pleased with the continued emphasis on cooperation along the long international border between the two countries noting that this sub region constitutes a single epidemiological block, due to population movement, shared nomadic groups, and border populations that straddle the border. The principle challenge remains the shared common poliovirus reservoirs between both countries.
The Committee noted that there were no new WPV1 cases detected in Nigeria since August 2016. However, as there remains a substantial population in Northern Nigeria that is totally or partially inaccessible, the committee concluded that there is a high risk that polioviruses are still circulating in this sub-region. Reaching these populations is critically important for the polio eradication effort, but it is acknowledged that there are significant security risks that may pose a 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 these innovations should be continued. Nigeria also reported on ongoing efforts to ensure vaccination at international borders (including at airports), other transit points, IDP camps and in other areas where nomadic populations existed.
There was ongoing concern about the Lake Chad basin region, and for all the countries that are affected by the 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 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 of immunization and surveillance activities.
While Equatorial Guinea remains vulnerable, the committee was pleased that there had been some recent improvement in AFP surveillance and a plan to introduce environmental surveillance. The plan to address gaps in population immunity through SIA’s and improvements to routine immunization are welcomed and should be monitored to ensure success.
The Netherlands reported an incident in which a breach of containment at a vaccine manufacturing plant led to the infection of a worker with WPV2 at a vaccine manufacturing plant. This event is serious and subject to ongoing monitoring, but the committee noted that some important lessons can be learnt in the response to this event. While the risk of international spread is very low, the public health consequences of any further transmission of this eradicated virus would be extremely serious.
Vaccine derived poliovirus
The committee noted that there were no new outbreaks of cVDPV, and no new cases in the three current cVDPV2 outbreaks (Borno and Sokoto in northern Nigeria, and in Quetta Pakistan). However, these outbreaks highlighted the presence of vulnerable under immunized populations in countries with endemic transmission. The committee noted the comprehensive response to these outbreaks.
The Russian Federation provided an update on the actions taken following the detection of VDPV2s in two children from the Chechen Republic and Moscow, but the committee noted there were still some important gaps in the information and the final classification of the case is therefore pending. However, the surveillance and immunization activities taken in response to this event were welcomed, and there appears to be very little risk of international spread.
In Lao PDR, the most recent case of cVDPV had onset in January 2016, and based on the most recent outbreak response assessment and the criteria of the committee, the country is no longer considered as infected, but remains vulnerable.
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 revised Temporary Recommendations for a further three months. The Committee considered the following factors in reaching this conclusion:
The continuing international spread of WPV1 between Pakistan and Afghanistan in the last 3 months.
The potential risk of further spread through population movement, whether for family, social and cultural reasons, or in the context of populations displaced by insecurity, returning refugees, or nomadic populations, and the need for international coordination to address these risks, particularly between Afghanistan and Pakistan, and Nigeria and its Lake Chad neighbors.
The current special and extraordinary context of being closer to polio eradication than ever before in history, with the incidence of WPV1 cases in 2017 the lowest ever recorded.
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 an increasing probability.
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 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 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.
Notwithstanding the concept that Afghanistan and Pakistan form a single epidemiological block with shared poliovirus reservoirs straddling the international border, in the context of the IHR, transmission across the border constitutes international spread between State Parties. Many other State Parties equally share cross border populations with neighboring countries, and form epidemiological blocks with respect to disease transmission. The existence of such epidemiological blocks does not negate the actual or potential public health risk to other States through international spread, requiring a coordinated international response, pre-conditions for determining a PHEIC under the IHR.