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Notes from the Field: Readiness for Use of Type 2 Novel Oral Poliovirus Vaccine in Response to a Type 2 Circulating Vaccine-Derived Poliovirus Outbreak — Tajikistan, 2020–2021

2022; Centers for Disease Control and Prevention; Volume: 71; Issue: 9 Linguagem: Inglês

10.15585/mmwr.mm7109a4

1545-861X

Patrick O’Connor, Shahin Huseynov, Carrie Nielsen, Faizali Saidzoda, Eugene Saxentoff, Umeda Sadykova, Patricia Kormoss,

Respiratory viral infections research

On January 13, 2021, a vaccine-derived poliovirus type 2 (VDPV2) was identified by the Regional Reference Laboratory for Polio in Moscow, Russia* in a specimen from a patient with acute flaccid paralysis (AFP) in Jaloliddin Balkhi district, Khatlon Region, in Tajikistan.Paralysis onset occurred on November 22, 2020.On February 6, 2021, a second, genetically linked VDPV2 paralytic case, with onset of paralysis on January 17, 2021, was confirmed from Khatlon Region in the neighboring Vakhsh district, indicating local transmission.Genetic sequencing of the isolate by the Regional Reference Laboratory for Polio in Moscow found a 20-nucleotide divergence from Sabin vaccine virus strain, and a 14-nucleotide divergence from a circulating VDPV2 (cVDPV2) reported from Khikorgangi, Pakistan on December 7, 2020, which suggests undetected circulation for approximately 12 months (1).On the basis of high-quality AFP surveillance in Tajikistan, the researchers concluded these cases likely represent recent importation (2).During 2014, the Director-General of the World Health Organization (WHO) declared polio a Public Health Emergency of International Concern under the International Health Regulations; the isolation of any poliovirus requires immediate reporting and prompt response (3).Children born after the global cessation of use of type 2containing oral poliovirus vaccine (OPV) from routine immunization schedules in April 2016 have no mucosal immunity against type 2 polioviruses.Therefore, cVDPV2 outbreak immunization responses require the use of type 2-containing OPVs; however, in low-coverage settings, use of type 2 oral poliovirus vaccine increases the risk for seeding † of new * Tajikistan does not have a national polio laboratory; therefore, specimens are transported to the Regional Reference Laboratory for Polio in Moscow, Russia for testing on a regular basis.During the COVID-19 pandemic, regularly scheduled flights to and from Tajikistan were interrupted, and this affected the transportation of specimens.† Oral poliovirus vaccines are live attenuated virus vaccines and provide intestinal immunity; poliovirus replicates in the intestinal tract.The vaccine virus is excreted in stool and can spread from person to person.However, in communities with low immunization coverage, vaccine virus can circulate during an extended period leading to reversion to neurovirulence, which can result in paralysis identical to that caused by wild polioviruses.https://www.cdc.gov/vaccines/vpd/polio/hcp/vaccine-derived-poliovirus-faq.html