Disease Outbreak News

Circulating vaccine-derived poliovirus type 2 – Ukraine

22 October 2021

Description of the situation

On 2 October 2021, WHO was notified of the isolation of poliovirus in the samples from an acute flaccid paralysis (AFP) case in Ukraine. The individual is a 17-month old female who had onset of paralysis on 3 September. Poliovirus type 2 was confirmed on 1 October by the Regional Reference Lab (RRL) in Helsinki, Finland, and further genetic sequencing at RRL confirmed vaccine-derived poliovirus type 2 (VDPV2) on 6 October. The same virus has also been isolated from six healthy siblings of the case. The family is from Rivne province, in the northwest of Ukraine.

Genetic sequencing indicates the virus is closely linked with an environmental isolate in Tajikistan. Local authorities, along with WHO regional and country teams, are conducting further investigations to determine the source of the infection, and to ascertain any potential risk of further spread. Therefore, the current outbreak was classified as circulating VDPV2 (cVDPV2).

Previously, an outbreak of circulating VDPV type 1 (cVDPV1) was reported in Ukraine in 2015, resulting in two cases. The last reported VDPV was classified as VDPV2 in Ukraine’s Odesa province in 2016. The virus isolated from the current reported case in Rivne is not related to the 2015 outbreak or 2016 isolates.

The national immunization coverage with three doses of polio vaccine (POL3) in Ukraine was 83% in 2020.

Public health response

The Ministry of Health led multi-disciplinary emergency task force has been established to coordinate the public health response. Partners of the Global Polio Eradication Initiative (GPEI), including WHO, are providing support to authorities at national and subnational levels. This support includes outbreak investigation, intensified surveillance, and raising public awareness.

Supplemental vaccination of all young children in the affected area is planned to ensure catch-up for any eligible children who may have missed routine polio vaccination and ensure that all are protected from the disease.

WHO risk assessment

The risk of national spread is assessed as high due to historically low immunization coverage rates in Ukraine and the existing subnational vaccination gaps. Although AFP surveillance is sensitive enough to detect paralytic cases, poliovirus transmission may continue undetected.

The risk of international spread of this virus is currently assessed as low due to the relatively high immunization coverage and sanitary infrastructure in neighboring countries, particularly Belarus, Hungary, and Slovakia. However, the European Regional Commission for Certification of Polio Eradication expressed concern about the quality of polio surveillance and suboptimal vaccination coverage in Poland and Romania.

WHO advice

It is important that all countries, particularly those with frequent travel and contacts with polio-affected countries and areas, strengthen the surveillance of AFP cases in order to rapidly detect any new poliovirus importations and to facilitate a rapid response. Countries, territories, and areas should also maintain systematically high routine immunization coverage rates at subnational levels to minimize the consequences of any new poliovirus introduction.

WHO’s International Travel and Health recommends that all travelers 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 oral poliovirus vaccine (OPV) or inactivated poliovirus vaccine (IPV) within four weeks to 12 months of travel.

Countries affected by poliovirus circulation are subject to temporary recommendations issued by the Emergency Committee of the International Health Regulations on Polioviruses, due to the declared Public Health Emergency of International Concern (PHEIC). The latest report by the Committee is from August 2021.