The Global Polio Eradication Initiative (GPEI) is extremely concerned about the unfolding effects of the current crisis in Ukraine on the country’s health system.  A functioning health system must be kept neutral and protected from all political or security issues affecting countries, to ensure that people have continued access to critical and essential care.

At the same time, we have seen time and again that large-scale population movements, insecurity and hampered access contribute greatly to the emergence and/or spread of infectious diseases, such as polio.

Ukraine is currently affected by a circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreak, with the most recent case detected in January 2022 (with disease onset in December 2021).

A national supplemental polio immunization campaign targeting nearly 140,000 children throughout Ukraine who had not been vaccinated against polio began on 1 February 2022, but is currently paused, as health authorities have shifted focus towards emergency services. Surveillance to detect and report new cases of polio is also disrupted, increasing the risk of undetected spread of the disease among vulnerable populations. The GPEI is working to urgently develop contingency plans to support Ukraine and prevent further spread of polio.

The GPEI has a long history of working in a variety of complex environments, and will continue to adapt its operations to the reality on the ground, to the degree possible, without compromising on the safety and security of health workers.  At the same time, immunization and surveillance is being assessed in neighbouring countries, to minimize the risk and consequences of any potential infectious disease emergence/spread resulting from the current large-scale population movements.  It is critical that necessary resources are mobilized and made available to assist with the humanitarian needs, including relief, disease response/prevention efforts both in Ukraine and in neighbouring countries.

Boy receiving polio drops from a health worker, with his mother during a polio vaccination campaign in 2015. © WHO / Alex Shpigunov
Boy receiving polio drops from a health worker, with his mother during a polio vaccination campaign in 2015. © WHO / Alex Shpigunov

A poliomyelitis (polio) vaccination campaign for children aged 6 months to 6 years who missed routine polio doses in the past will begin in Ukraine on 1 February 2022. This catch-up campaign is part of a comprehensive response to stop an outbreak of poliovirus first detected in Ukraine in October 2021. This first stage will last 3 weeks and is expected to reach nearly 140 000 children throughout the country.

Years of low immunization coverage in Ukraine have created a large pool of unvaccinated or under-vaccinated children who are vulnerable to polio. While routine immunization coverage has gradually increased over the past 6 years, in 2020, only 84% of 1-year-olds received the required 3 scheduled doses of polio vaccines by 12 months of age.

The immediate goal of the campaign is to reach the WHO-recommended level of 95% vaccination coverage of eligible children.

Background

The polio outbreak in Ukraine was confirmed on 6 October 2021. Poliovirus (circulating vaccine-derived poliovirus type 2) was first isolated in a 17-month-old girl in the province of Rivne who developed acute flaccid paralysis. Analysis of all her contacts found that 7 household contacts (siblings) and 8 community contacts in Rivne as well as 4 cousins in the province of Zakarpattya (who had had contact with the girl’s siblings) also tested positive, but did not develop paralytic symptoms.

A second case with acute flaccid paralysis (a 2-year-old boy in the region of Zakarpattya) also tested positive for poliovirus, with onset of paralysis in December 2021.

The isolated strain of the virus found in both paralytic cases and their contacts is linked to a poliovirus in Pakistan, which was also the cause of several cases in Tajikistan in 2020–2021.

Comprehensive plan to stop the spread of poliovirus

Following an initial local vaccination campaign, conducted where the first case was detected, a comprehensive polio outbreak response plan was approved by the Ministry of Health in December 2021.

The first stage of the plan will provide inactivated polio vaccine (IPV) to children aged 6 months to 6 years who have not received the required number of doses. In the second stage, all children under the age of 6 will be vaccinated with oral polio vaccine (OPV), even if they have received all their scheduled vaccination doses. This is necessary to protect children from infection and to stop the circulation of the virus. Dates for the second stage are pending.

WHO/Shpigunov

A team of technical experts assessed Ukraine’s response to a polio outbreak and concluded that transmission of poliovirus has been interrupted. Nevertheless, the team remains concerned about significant gaps in immunization and surveillance that put Ukraine at high risk for new outbreaks.

“Thanks to the efforts of the Ministry of Health, health workers and parents, many more children are vaccinated against polio, and I commend them for their commitment,” said Dr Zsuzsanna Jakab, WHO Regional Director for Europe. “But these efforts do not stop now. The immunization gap persists and, if Ukraine does not continue vaccinating its children, this gap will expand for polio and other vaccine-preventable diseases to strike.”

High routine immunization coverage

Owing to low coverage, immunization gaps accumulated in Ukraine; it interrupted polio transmission with a campaign of three rounds of catch-up vaccination. High routine immunization coverage is a top priority for WHO, to ensure that another outbreak of polio or any other vaccine-preventable disease does not hit the country.

“We need to seize the momentum gained during the polio outbreak to strengthen Ukraine’s immunization programme, so that parents may exercise their right and responsibility to vaccinate their children,” said Dr Luigi Migliorini, WHO Representative in Ukraine.

With the United Nations Children’s Fund (UNICEF), WHO is supporting the Ministry of Health in making vaccines available to close the country’s immunization gap and protect against all vaccine-preventable diseases.

Recommendations of the expert team

An expert team from different United Nations agencies and partners assessed the polio-outbreak response over two weeks in five Ukrainian regions, at both oblast and rayon levels. Experts analysed the disease surveillance systems, supplementary immunization activities, and communications “, said Dr Patrick O’Connor, leader of the WHO assessment team.

As well as concluding that poliovirus transmission in Ukraine had been interrupted, the team recommended key actions to mitigate the risk of future outbreaks:

• increase political commitment for childhood immunization;

• re-establish high, uniform immunization coverage with polio vaccines;

• improve the communication skills of frontline health workers; and

• enhance surveillance for early detection of polioviruses.

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Girl proudly displaying her marked finger, indicating that she has been vaccinated against polio. © Unicef
Girl proudly displaying her marked finger, indicating that she has been vaccinated against polio.
© Unicef

In Ukraine, 2 cases of circulating vaccine-derived poliovirus type 1 (cVDPV1) have been confirmed, with dates of onset of paralysis of 30 June and 7 July 2015. The genetic similarity between the cases indicates active transmission of cVDPV1. Both are from the Zakarpatskaya oblast, in south-western Ukraine, bordering Romania, Hungary, Slovakia and Poland. One child was 4 years old and the other 10 months old at the time of onset of paralysis.

Ukraine had been at particular risk of emergence of a cVDPV, due to inadequate vaccination coverage. In 2014, only 50% of children were fully immunized against polio and other vaccine-preventable diseases.

Discussions are currently ongoing with national health authorities to plan and implement an urgent outbreak response. An outbreak response of internationally-agreed standard, as adopted by the World Health Assembly in May 2015, requires a minimum of three large-scale supplementary immunization activities with an appropriate oral polio vaccine, to begin within two weeks of confirmation of the outbreak and covering a target population of 2 million children aged less than five years, and the public declaration of the outbreak as a national public health emergency.

Circulating VDPVs are rare but well-documented strains of poliovirus that can emerge in some populations which are inadequately immunized. A robust outbreak response can rapidly stop such events. The emergence of cVDPV strains underscores the importance of maintaining high levels of routine vaccination coverage.

It is important that all countries, in particular those with frequent travel and contacts with polio-affected countries and areas, strengthen surveillance for AFP cases in order to rapidly detect any new virus importation or emergence and to facilitate a rapid response. Countries 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 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 OPV or inactivated polio vaccine (IPV) within 4 weeks to 12 months of travel.

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