Why the study?
Pakistan has experienced a surge in wild poliovirus type 1 cases and spread, an outbreak of circulating vaccine-derived poliovirus type 2, and COVID-19 pandemic-related disruption of polio vaccination delivery.
The resurgence of WPV1 and emergence of cVDPV2 in Pakistan highlight the urgent need to resume high-quality vaccination campaigns disrupted by the COVID-19 pandemic.
Supports intensified surveillance and immunization in endemic regions; leaves open optimal strategies for interrupting expanded transmission.
Pakistan and Afghanistan are the only countries where wild poliovirus type 1 (WPV1) is endemic (1,2). In 2019, Pakistan reported 147 WPV1 cases, approximately 12 times the number reported in 2018. As of September 15, 72 cases had been reported in 2020. Since 2019, WPV1 transmission has also spread from Pakistan's core poliovirus reservoirs (Karachi, Peshawar, and Quetta block) to southern districts of Khyber Pakhtunkhwa (KP), Punjab, and Sindh provinces. Further, an outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2), first detected in July 2019, has caused 22 paralytic cases in 2019 and 59 as of September 15, 2020, throughout the country. The coronavirus disease 2019 (COVID-19) pandemic has substantially reduced delivery of polio vaccines through essential immunization (formerly routine immunization) and prevented implementation of polio supplementary immunization activities (SIAs)* during March-July 2020. This report describes Pakistan's progress in polio eradication during January 2019-September 2020 and updates previous reports The Pakistan polio program has reinitiated SIAs and will need large, intensive, high-quality campaigns with strategic use of available oral poliovirus vaccines (OPVs) to control the surge and widespread transmission of WPV1 and cVDPV2.
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Hsu et al. (2020) studied this question.
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