Questions and answers about poliovirus containment

The WHO European Region has been free from endemic poliomyelitis (polio) since 2002. The wild virus is no longer circulating and causing illness in the Region, and it is endemic in only three remaining countries worldwide. The slight risk of emergence of vaccine-derived strains in areas with low coverage using only the oral polio vaccine (OPV) has been addressed by the shift to or addition of the inactivated polio vaccine, as part of the global polio vaccine “switch” in 2016.

As global eradication approaches, comprehensive work has begun on polio containment – the final step in ridding the Region, and the world, of a crippling disease.

What is poliovirus containment?

Wherever a sample of poliovirus is held – for example, in the laboratory of an academic institution or an industrial facility – WHO needs to be informed of its presence and the infectious sample must be made safe and secure.

There are three ways to deal with the virus.

  1. It can be destroyed by heating to a high temperature under increased air pressure. This needs to be registered, done in the presence of witnesses and reported to WHO along with the supporting documentation. In the majority of situations, this is the option recommended by WHO and preferred by the country in which the laboratory is located.
  2. It can be transferred to a laboratory in the same or another country that is (or is on its way to becoming) certified to store it safely and securely. Laboratories or facilities certified to retain the virus are known as poliovirus essential facilities (PEFs).
  3. The laboratory holding the sample may seek its country’s approval to become a PEF and commit to complying with stringent certification criteria to continue holding samples. There are no certified PEFs yet anywhere in the world.

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Why do we need to do this?

Containment reduces the risk of the virus accidentally escaping a facility and infecting someone, or falling into the hands of someone with malicious intent. Following global efforts to increase vaccination rates, reduce the number of cases to almost zero and maintain high-quality surveillance, containment is the last remaining step on the road to polio eradication.

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How much progress has the WHO European Region made?

The initial lengthy process of logging where poliovirus is held in the Region has been completed. Now each academic institution or manufacturing facility that holds the virus must decide which containment option to pursue, in accordance with global agreements.

Over time, any samples overlooked in this initial round will come to light. Preparedness plans for this possibility and for any potential breaches of containment are also being put in place.

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How is poliovirus stored and who has it in the Region?

Poliovirus is normally stored in vials in freezers and is held in a surprisingly wide range of institutions. Vaccine manufacturers, for example, need to have poliovirus stocks in order to make vaccines. Academic institutions currently hold samples for teaching virology; however, they could use other similar viruses instead, to minimize the risk. Manufacturers of detergents and cleaning products may also use poliovirus to test the quality of their products. In this instance another virus could be substituted, but that may require a change in national regulations. Finally, many research and clinical virology laboratories possess stocks of polioviruses and now have to make a decision about these in order not to compromise the success of the containment process.

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How many PEFs does the Region need?

Using smallpox as an example, there are two smallpox containment facilities in the world, so it is certainly not necessary or desirable for every Member State to have a PEF.

As of October 2017, 12 Member States in the European Region have notified WHO that more than 30 institutions or manufacturing facilities plan to apply for PEF status. This status will be determined by a national authority on containment in each of these countries.

At this time it is difficult to predict how many of those applying for certification would be able to comply with the stringent safety and security criteria imposed by the certification scheme. The process of certification is long and costly, both in financial terms and in terms of human resources. A larger number of PEFs means a higher risk of an accidental release of the virus.

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Will the risk of polio resurgence ever be eliminated?

The world will be a safer place once all three types of wild poliovirus have been eradicated everywhere. While the potential risk posed by the virus will never reach zero, it can be reduced to the lowest possible level. Containment is essential to this, and full commitment to containment is required forever.

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