WHO conducted an outbreak response evaluation from April 11 to 15, 2022, and found that the poliovirus is no longer circulating in Tajikistan, recommending the outbreak’s official closure.
Poliomyelitis (polio) is a contagious disease with no borders. The virus’s importation and subsequent propagation paralysed 34 children, while 26 others tested positive but did not develop paralysis symptoms. Tajikistan has not tested positive for any child, adult, or environmental sample since August 2021.
The epidemic in Tajikistan was the first time circulating vaccine-derived poliovirus type 2 (cVDPV2) was found in the WHO European Region. The world’s first cVDPV2 epidemic has been declared officially closed following subsequent vaccination with the novel oral polio vaccine type 2. (nOPV2).
The Region has been polio-free since 2002. A single case of polio, whether caused by a wild or vaccine-derived poliovirus, is considered an outbreak, requiring immediate and comprehensive action.
Dr Hans Henri P. Kluge, WHO Regional Director for Europe, remarked, “Tajikistan’s success in limiting this outbreak is a fantastic accomplishment and a clear demonstration of the Government of Tajikistan’s highest degree of political commitment.”
“The outbreak and its aftermath struck at a time when the health system was already straining under the weight of the COVID-19 pandemic, and the country was gearing up to undertake a massive COVID-19 vaccine campaign. Both epidemic responses must be carried out without jeopardising the crucial availability of vaccines for other children. We congratulate the Ministry of Health’s efforts in recent years, which have resulted in a robust immunisation system capable of effectively addressing all of these competing immunisation needs.”
Stopping the epidemic
The Ministry of Health and Social Protection of the Population acted quickly after the pandemic was confirmed, with help and guidance from WHO and other GPEI partners. Among the efforts taken were increased poliovirus surveillance, thorough contact tracing, and a detailed review of immunisation coverage at the subnational level. After undertaking a thorough risk assessment to determine the outbreak response scale and vaccination of choice, the country promptly completed a full verification procedure for readiness to use the nOPV2 vaccine.
After the trivalent oral polio vaccine was phased out, a superior nationwide disabled polio vaccine movement was launched in February 2021 to close the immunity break against poliovirus type 2 among the over 500,000 children born between 2016 and 2018 who were left vulnerable due to global deactivated polio vaccine (IPV) supply constraints.
Between June and September 2021, all children under the age of six received two national and one subnational nOPV2 immunisation rounds, with coverage reaching 95%. (based on external assessment). Extensive social mobilisation and communication initiatives targeted internal migrants in urban areas, as well as unregistered children.
Evaluation of the epidemic’s reaction
Certain conditions must be met before an outbreak can be declared officially over, including no poliovirus detection for at least six months. The efficiency of routine polio vaccination, coverage obtained during supplemental immunisation rounds, and the capacity and sensitivity of the polio surveillance system to identify any poliovirus circulation were all examined in Tajikistan.
After performing a thorough review that included national briefings and ground visits to national referral hospitals, public hospitals, polyclinics, regional and district vaccination programme offices, and public health centres, the committee recommended that the outbreak be closed.
nOPV2 is a significant step forward in the global fight against polio.
The adoption of nOPV2 to stop this outbreak is a huge step forward for the global polio campaign. The new anti-cVDPV2 strategy relies heavily on the innovative vaccination. Clinical investigations have showed that nOPV2 is both safe and effective, with more genetic stability than the standard type 2 oral polio vaccine.
Since the initiative began in March 2021, about 265 million doses of nOPV2 have been distributed across 14 nations. However, this is the first time an epidemic has been declared over due to the use of nOPV2.
Tajikistan, with the support of WHO, contributed to worldwide nOPV2 research by conducting an immunogenicity study on the virus, as well as successfully preventing transmission and minimising the risk of infection for millions of people. In addition, the country performed a global vaccine waste research.