Tajikistan’s rapid and successful response to a polio outbreak amidst the COVID-19 pandemic

The first ever outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2) in the WHO European Region was confirmed in Tajikistan on 20 January 2021 after its importation from a neighboring country. As a result of type 2 oral polio vaccination global supply constraints in 2016, an estimated 520 000 Tajik children born between 2016 and 2018 stood vulnerable to infection. By August, 33 children were paralyzed, and the virus had been isolated from 26 healthy contacts and from 20 samples periodically collected from the sewer system in the capital city. From February to September, an unprecedented response to the poliovirus outbreak was mounted in terms of speed and quality despite competing COVID-19 pandemic priorities and the worsened security situation in the sub-region. Readiness verification for the use of novel vaccine in Tajikistan was conducted rapidly, and several rounds of quality immunization campaigns were implemented, covering more than 1.3 million children. Interim evidence from the 16 to 20 August 2021 outbreak response assessment indicated that cVDPV2 transmission in Tajikistan has already been interrupted. To determine if the outbreak can be declared closed, a final outbreak response assessment mission is planned by WHO for quarter 2 of 2022.

How did Tajikistan do it, and how did the WHO Secretariat support Tajikistan?

• Strengthening surveillance – Following confirmation of the outbreak, the Ministry of Health and Social Protection of the Population immediately acted upon the WHO Regional Office for Europe’s key recommendations on responding to Poliovirus Type 2 (PV2) for enhancing poliovirus (PV) surveillance. These are in line with Global Polio Eradication Initiative (GPEI) Standard Operating Procedures (SOP). Intensive contact tracing and sampling was conducted and immunization coverage was reviewed.
• Selecting the most appropriate vaccine – The Government of Tajikistan opted for use of a genetically stabilized, novel oral polio vaccine type 2 (nOPV2) which received WHO Emergency Use Listing status in November 2020. This decision was made by the Ministry of Health based upon a recommendation from, and extensive technical discussions with, the WHO Regional Office for Europe. A rigorous risk assessment was conducted to determine the outbreak response scale and nOPV2 was chosen as the best vaccine option both for the response and for protecting the polio-free status of the entire WHO European Region.
• Conducting vaccine readiness verification for the novel vaccine – With technical support from the WHO Country Office and Global Polio Eradication Initiative partners, Tajikistan documented the 25 Emergency Use Listing readiness criteria necessary for the initial use phase, enabling nOPV2 release within eight weeks. This made Tajikistan the first country outside of the WHO African Region authorized to use nOPV2. To fulfil outbreak monitoring and nOPV2 preparedness requirements, Tajikistan established functional environmental surveillance within record time; the first sample was collected by the week of 7 February 2021.
• Increasing vaccine coverage to close the immunity gap nationwide – In February, a high-quality nationwide inactivated polio vaccine campaign was conducted to close the immunity gap against poliovirus type 2 among the more than half a million children born from 2016 to 2018. An external evaluation supported by WHO confirmed high vaccination coverage. WHO covered financial costs, deployed an international expert to provide the required technical expertise, and trained local staff. Between June and September, three nOPV2 immunization rounds were implemented with coverage externally confirmed to be high (greater than 95%).
• Implementing specific strategies for hard-to-reach groups – To cover missed children during all three rounds of vaccination, a flexible outreach approach was used that could rapidly be adjusted as gaps in coverage were identified. During the second round of vaccinations to address low coverage, there was a COVID-19 case surge that affected human healthcare resources and vaccine uptake. Exemplary resilience was demonstrated in implementing immediate corrective measures. Extensive social mobilization and communication strategies were deployed to reach groups who were at risk of being missed. These included internal migrants in urban areas, communities close to the land borders with Afghanistan, Luli populations, and unregistered children.

Photo Credit: © M.Abidzhanov

Photo Caption: WHO staff monitoring the first round of the novel oral polio vaccine type 2 campaign.

In addition to successfully halting transmission and removing the risk of infection for millions of people, Tajikistan contributed to global research on the nOPV2 vaccine with the support of WHO through an nOPV2 immunogenicity study. The study was initiated by the Ministry of Health and WHO headquarters and the WHO Regional Office for Europe reviewed the design, financially supported the study, and arranged for samples to be tested in WHO’s global laboratory in Atlanta, Georgia, United States of America. The findings were presented in the Global Polio Research Committee Meeting on 7 April 2022. The country also participated in the global vaccine wastage study.

Tajikistan’s success was particularly notable as the health system was already overstretched by the COVID-19 pandemic and competing priorities posed a challenge. Preparation and implementation activities for the nOPV2 campaign occurred while the country was mounting a massive vaccination drive against COVID-19. Major efforts were also made to ensure that the provision of routine childhood vaccination services was not disrupted. Conducting training activities and organizing vaccination points at health facilities in the context of COVID-19 restrictions was challenging but primary health care staff demonstrated high motivation and determination to work during the pandemic. The high commitment of the national government was key for success. Strong national leadership, complemented by continuous and effective technical guidance and assistance from WHO and the Global Polio Eradication Initiative, was instrumental to a robust outbreak response.