Poliomyelitis (Circulating vaccine-derived poliovirus and Wild Poliovirus) – Global update

Quarantine Unit
Co-National Focal Point of International Health Regulations (IHR)-2005
Ministry of  Health, Sri Lanka 

Between 1 January and 14 October 2020, there have been several countries affected by poliomyelitis including circulating vaccine-derived poliomyelitis type 1 and 2 (cVDPV1 and cVDPV2) and wild poliovirus type 1 (WPV1) globally. This announcement is a weekly update on the status of cVDPV and WPV1 in these affected countries.

Between 8 and 14 October 2020, there have been four WPV1 in Acute Flaccid Paralysis (AFP) cases and four WPV1 positive environmental samples reported in Afghanistan and Pakistan. During the same period, there have been 23 cVDPV2 in AFP cases reported in Burkina Faso, Côte d’Ivoire, Guinea, Mali and Niger, and 21 cVDPV2 positive environmental samples reported in Afghanistan and Pakistan. Below is the description of the reported cases by country:

  • Afghanistan: one WPV1 in AFP case, one WPV1 positive environmental sample and 11 cVDPV2 positive environmental samples
  • Pakistan: three WPV1 in AFP cases, three WPV1 positive environmental samples and 10 cVDPV2 positive environmental samples
  • Burkina Faso: one cVDPV2 in AFP case
  • Côte d’Ivoire: four cVDPV2 in AFP cases
  • Guinea: eleven cVDPV2 in AFP cases
  • Mali: four cVDPV2 in AFP cases
  • Niger: three cVDPV2 in AFP cases

Please find below the link to the weekly global polio update published by the global polio eradication initiative (GPEI) that includes an update on polio (WPV 1, cVDPV1, and cVDPV2) case count for this week (between 8 and 14 October 2020) and cumulative case count by country since 1 January 2020.



Public Health Response

The Global Polio Eradication Initiative (GPEI) is continuing to support countries in their response implementation, including field, virologic, and epidemiological investigations, strengthening surveillance for acute flaccid paralysis and evaluating the extent of virus circulation.  GPEI staff in countries are supporting on adjusting routine immunization and outbreak response to the prevailing COVID-19 situation.

In 2019 and early 2020, the Global Polio Eradication Initiative developed the Strategy for the Response to Type 2 Circulating Vaccine-derived Poliovirus 2020-2021, an addendum to the Polio Endgame Strategy 2019-2023 to more effectively address the evolving cVDPV2 epidemiology, which will drive outbreak response in 2020 and 2021.  Necessary adaptations of delivery strategy and timelines are continuously being made.

Accelerating the development of novel oral polio vaccine type 2 (nOPV2) and enabling its use is an important step forward for GPEI. The new vaccine is anticipated to have a substantially lower risk of seeding new type 2 vaccine-derived polioviruses compared to mOPV2.


WHO risk assessment

The continued spread of existing outbreaks due to circulating vaccine-derived poliovirus type 2 as well as the emergence of new type 2 circulating vaccine-derived polioviruses points to gaps in routine immunization coverage as well as the insufficient quality of outbreak response with monovalent oral polio vaccine type 2. The risk of further spread of such strains, or the emergence of new strains, is magnified by an ever-increasing mucosal-immunity gap to type 2 poliovirus on the continent, following the switch from trivalent to bivalent oral polio vaccine in 2016.

The detection of cVDPV2s underscores the importance of maintaining high routine vaccination coverage everywhere to minimize the risk and consequences of any poliovirus circulation. These events also underscore the risk posed by any low-level transmission of the virus. A robust outbreak response is needed to rapidly stop circulation and ensure sufficient vaccination coverage in the affected areas to prevent similar outbreaks in the future. WHO will continue to evaluate the epidemiological situation and outbreak response measures being implemented.

The COVID-19 pandemic is continuing to affect the global polio eradication effort. Given that operationally polio vaccination campaigns are close-contact activities, they are incompatible with the current global guidance on physical distancing regarding the COVID-19 response efforts. As such, the programme has taken a very difficult decision to temporarily delay immunization campaigns. The overriding priority is to ensure the health and safety of health workers as well as communities. All GPEI recommendations are in line with those on essential immunization and are available here.

The programme has implemented a two-pronged approach to minimize the risk of an increase in polio cases, particularly in areas which are affected by the disease and possibly a spread of the virus to other areas.

  1. The programme will continue, to the extent possible, its surveillance activities to monitor the evolution of the situation.
  2. The programme aims to return to action in full strength including with vaccination campaigns, as rapidly as is safely feasible. The timing will depend on the local situation and the programme will then need to operate in the context of the respective countries national health systems risk assessments and priorities.  Comprehensive, context-specific plans to resume efforts are being developed, to be launched whenever and wherever the situation allows.

In many countries, polio assets (e.g., personnel, logistics, operations) are assisting national health systems to respond to the COVID-19 pandemic and help ensure the crisis is dealt with as rapidly and effectively as possible.


WHO advice

It is important that all countries, in particular those with frequent travels and contacts with polio-affected countries and areas, strengthen surveillance for acute flaccid paralysis (AFP) cases in order to rapidly detect any new virus importation and to facilitate a rapid response. Countries, territories and areas should also maintain uniformly high routine immunization coverage at the district level to minimize the consequences of any new virus introduction.

WHO’s International Travel and Health recommends that all travellers to polio-affected areas be fully vaccinated against polio. Residents (and visitors for more than 4 weeks) from infected areas should receive an additional dose of OPV or inactivated polio vaccine (IPV) within 4 weeks to 12 months of travel.

As per the advice of an Emergency Committee convened under the International Health Regulations (2005), efforts to limit the international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC). Countries affected by poliovirus transmission are subject to Temporary Recommendations. To comply with the Temporary Recommendations issued under the PHEIC, any country infected by poliovirus should declare the outbreak as a national public health emergency and consider vaccination of all international travelers.


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Author: SLCM