Top 5 Takeaways

1. Significant Increase in cVDPV2 Cases: During January 2020–June 2021, there were 44 cVDPV outbreaks resulting in 1,335 paralytic cases, with 86% being cVDPV2.
2. Introduction of Novel OPV2: The novel type 2 oral poliovirus vaccine (nOPV2), more genetically stable than the Sabin strain, was first used in March 2021 for outbreak responses.
3. Geographical Spread: cVDPV2 outbreaks affected 34 countries, with 82% of these countries located in Africa.
4. Impact of COVID-19: The COVID-19 pandemic disrupted surveillance and immunization activities, potentially leading to undercounts and delayed detection of cVDPV2 outbreaks.
5. Strategic Goals: The Global Polio Eradication Initiative aims to interrupt all cVDPV2 transmission by the end of 2023 through improved outbreak detection and response strategies.

Original Article Author and Citation

Corresponding Author

Mary M. Alleman, mea4@cdc.gov

Suggested Citation

Alleman MM, Jorba J, Henderson E, et al. Update on Vaccine-Derived Poliovirus Outbreaks — Worldwide, January 2020–June 2021. MMWR Morb Mortal Wkly Rep 2021;70:1691–1699. DOI: http://dx.doi.org/10.15585/mmwr.mm7049a1

Summary

This report updates the status of circulating vaccine-derived poliovirus (cVDPV) outbreaks worldwide from January 2020 to June 2021. During this period, 44 cVDPV outbreaks were ongoing, resulting in 1,335 paralytic cases, with 38 of these outbreaks being cVDPV type 2 (cVDPV2). The novel type 2 oral poliovirus vaccine (nOPV2), which is more genetically stable than the Sabin strain, was introduced in March 2021 for outbreak responses. However, the supply of nOPV2 is currently limited. The Global Polio Eradication Initiative aims to improve early detection and response to cVDPV2 outbreaks to interrupt transmission by the end of 2023.

Methods

The report utilized data from environmental surveillance and acute flaccid paralysis (AFP) case investigations to detect and monitor cVDPV outbreaks. The data were collected from 37 countries affected by cVDPV outbreaks during the reporting period. The analysis included genetic sequencing to link poliovirus isolates to specific outbreaks and track their spread.

Discussion

The report highlights the significant challenge posed by cVDPV2 outbreaks, particularly in Africa, where 82% of the affected countries are located. The COVID-19 pandemic disrupted surveillance and immunization activities, leading to potential undercounts and delayed outbreak detection. The introduction of nOPV2 is a critical step in addressing cVDPV2 outbreaks, but its limited supply poses a challenge. The Global Polio Eradication Initiative’s 2022–2026 Strategic Plan aims to improve outbreak detection and response to achieve the goal of interrupting cVDPV2 transmission by the end of 2023.

Conclusion

cVDPV outbreaks continue to be a significant public health challenge, with a notable increase in cVDPV2 cases during the reporting period. The introduction of nOPV2 offers hope for better outbreak control, but supply limitations and the impact of the COVID-19 pandemic complicate efforts. The Global Polio Eradication Initiative’s strategic goals focus on improving early detection and response to cVDPV2 outbreaks to achieve interruption of transmission by the end of 2023.

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