Partners in the Global Polio Eradication Initiative (GPEI), including WHO, the United Nations Children’s Fund (UNICEF), and the United States Centers for Disease Control and Prevention (CDC), conducted an assessment of the overall response in Ukraine to an outbreak of paralytic poliomyelitis (polio) first detected in the country in October 2021.
The outbreak response assessment (OBRA), conducted on 23–26 May 2023, aimed to evaluate the risk of undetected transmission of poliovirus in Ukraine by reviewing the surveillance, vaccination and communication activities implemented in the outbreak response.
The OBRA team determined that despite the significant challenges faced by the outbreak response and disruptions to the health system due to the ongoing crisis in Ukraine, there was sufficient evidence to conclude that poliovirus is not circulating undetected in the country. The team therefore recommended that WHO/Europe consider officially closing the outbreak. The next step will be to verify that no poliovirus has been imported from Ukraine to neighbouring countries.
Comprehensive outbreak response
The outbreak began in Ukraine after the importation and subsequent circulation of vaccine-derived poliovirus type 2 (cVDPV2), linked to a previous outbreak in Tajikistan in 2021. Two children in Ukraine developed paralytic infections, and 19 healthy close contacts tested positive without developing symptoms.
Since 2002 the WHO European Region has remained free from endemic poliovirus, and in 2022 it celebrated 20 years of this status. However, even a single case of polio, whether caused by a wild or vaccine-derived poliovirus, is considered an outbreak and triggers an urgent response.
A nationwide immunization catch-up campaign with poliovirus vaccine began in Ukraine in February 2022 and has continued despite a number of challenges. Mass movement of the population, particularly women and children, has posed difficulties in reaching the target age group for polio vaccination. Additionally, the war in Ukraine has shifted the priorities of the population towards safety and survival, resulting in vaccination becoming a lower priority. The destruction of health-care facilities has further hindered the response efforts.
Despite these barriers, as of 7 May 2023, a total of 176 262 doses of inactivated polio vaccine (IPV) had been administered as part of the catch-up campaign.
“Ukraine's remarkable achievement in halting polio transmission amidst the ongoing war reflects the unwavering commitment and resilience of the Government and Ministry of Health,” said Dr Jarno Habicht, WHO Representative in Ukraine.
“It also demonstrates the exceptional dedication and tenacity of the country’s health workers, who have surmounted numerous challenges to reach children with vaccines that will protect them from this additional threat to their lives. The successful implementation of high-quality disease surveillance and provision of routine vaccines amidst such adversity is truly commendable.”
Assessment and recommendations
The decision to officially close a polio outbreak requires several criteria to be met, including at least 6 consecutive months without detection of poliovirus in the country.
The OBRA team conducted a comprehensive evaluation of disease surveillance, vaccination, vaccine logistics, laboratory capabilities and communication efforts since the confirmation of the outbreak in October 2021. On field visits to Kyiv, Chernihiv and Zhytomyr oblasts, they visited the regional centres for disease control and prevention, regional children’s infectious disease hospitals, and polyclinics. These visits enabled the team to assess the situation on the ground and gather crucial insights to support the overall assessment of the polio response activities conducted.
The Public Health Centre of the Ministry of Health and the Rivne and Zakarpattya regional centres for disease control and prevention played a crucial role in providing valuable information on the response at the national level and in the areas of the country where the 2 cases occurred.
Despite the immense challenges and uncertainties faced in Ukraine due to the ongoing war, the OBRA team did not find any evidence of continued transmission of cVDPV2 in Ukraine. Based on this, the OBRA team recommended that WHO/Europe consider officially closing the polio outbreak.
Recognizing the massive movement of refugees from Ukraine into neighbouring countries, the team also requested that WHO/Europe collate information on performance of vaccination and surveillance from neighbouring countries receiving Ukrainian migrants. WHO/Europe is currently reviewing data from 7 countries to assess the risk of spread related to the refugee crisis.
Polio outbreak response activities in Ukraine were supported financially by GPEI partners including the CDC, the United States Agency for International Development, and the Bill & Melinda Gates Foundation.