Circulating vaccine-derived poliovirus type 1 – Myanmar

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On 23 June 2019, a vaccine-derived poliovirus type 1 (VDPV1) was isolated from a two -year- old child with acute flaccid paralysis (AFP), with onset of paralysis on 22 May 2019 from Kayin state, Myanmar. Subsequently, on 11 July 2019, a genetically linked VDPV1 was isolated from the same state from a 5-year 6-month-old child with AFP, with date of onset of paralysis on 14 June, and it was classified as circulating VDPV1 (cVDPV1) on 12 July 2019. On 25 July 2019, cVDPV1 was isolated from a third AFP case from the same state, with date of onset of paralysis on 23 May 2019. Subsequently, on 19 August 2019, a fourth case of VDPV1 has been confirmed in a six-year-old child, with onset of paralysis on 23 July 2019. The child has no history of vaccination with OPV. In addition, the virus has also been isolated from seven healthy community contacts. These linked viruses have 25 to 31 nucleotide changes from Sabin 1. All cases and contacts are from Hpapun township of Kayin state, Myanmar.

Myanmar’s routine immunization coverage is estimated at 91% for three doses of bivalent oral polio vaccine (bOPV) in 2018. Neighbouring countries including Thailand and other countries in South East Asia have been informed of the confirmed cVDPV1, and subnational surveillance is being strengthened across the region. In 2018, Myanmar and Kayin state met certification standards for AFP surveillance with non-polio AFP rate of 3.45, and stool adequacy rate of 100% for Kayin state.

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