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Case Reports
. 2023 Apr 6;41 Suppl 1(Suppl 1):A48-A57.
doi: 10.1016/j.vaccine.2023.02.035. Epub 2023 Feb 17.

Genetic and epidemiological description of an outbreak of circulating vaccine-derived polio-virus type 2 (cVDPV2) in Angola, 2019-2020

Alda Morais  1 , Joana Morais  1 , Miguel Felix  1 , Zoraima Neto  1 , Valódia Madaleno  1 , Abubakar Sadiq Umar  2 , Nirakar Panda  2 , Fekadu Lemma  2 , José Alexandre Lifande Chivale  2 , Danielle Graça Cavalcante  2 , Elizabeth Davlantes  3 , Margherita Ghiselli  4 , Catherine Espinosa  4 , Ari Whiteman  5 , Jane Iber  6 , Elizabeth Henderson  6 , Kelley Bullard  6 , Jaume Jorba  6 , Cara C Burns  6 , Ousmane Diop  7 , Nicksy Gumede  8 , Lerato Seakamela  9 , Wayne Howard  9 , Alean Frawley  10
Affiliations
Case Reports

Genetic and epidemiological description of an outbreak of circulating vaccine-derived polio-virus type 2 (cVDPV2) in Angola, 2019-2020

Alda Morais et al. Vaccine. .

Abstract

After six years without any detection of poliomyelitis cases, Angola reported a case of circulating vaccine-derived poliovirus type 2 (cVDPV2) with paralysis onset date of 27 March 2019. Ultimately, 141 cVDPV2 polio cases were reported in all 18 provinces in 2019-2020, with particularly large hotspots in the south-central provinces of Luanda, Cuanza Sul, and Huambo. Most cases were reported from August to December 2019, with a peak of 15 cases in October 2019. These cases were classified into five distinct genetic emergences (emergence groups) and have ties with cases identified in 2017-2018 in the Democratic Republic of Congo. From June 2019 to July 2020, the Angola Ministry of Health and partners conducted 30 supplementary immunization activity (SIA) rounds as part of 10 campaign groups, using monovalent OPV type 2 (mOPV2). There were Sabin 2 vaccine strain detections in the environmental (sewage) samples taken after mOPV2 SIAs in each province. Following the initial response, additional cVDPV2 polio cases occurred in other provinces. However, the national surveillance system did not detect any new cVDPV2 polio cases after 9 February 2020. While reporting subpar indicator performance in epidemiological surveillance, the laboratory and environmental data as of May 2021 strongly suggest that Angola successfully interrupted transmission of cVDPV2 early in 2020. Additionally, the COVID-19 pandemic did not allow a formal Outbreak Response Assessment (OBRA). Improving the sensitivity of the surveillance system and the completeness of AFP case investigations will be vital to promptly detect and interrupt viral transmission if a new case or sewage isolate are identified in Angola or central Africa.

Keywords: Angola; Poliomyelitis; Type 2; Vaccination campaigns; Vaccine-derived.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1.
Fig. 1.
Post-switch cVDPV2 distribution in Angola, by emergence group and specimen date.* *AFP cases in red circles, environmental samples in green circles.
Fig. 2.
Fig. 2.
Location of isolations of cVDPV2 by emergence group (color), and specimen source (outline shape: circles for AFP cases or contacts/community; diamond for environmental surveillance [ENV]), Angola, 2019–2020.
Fig. 3.
Fig. 3.
Bayesian phylogenetic tree of VP1 sequences (903 nucleotides) of 2019–2020.**191 isolates representing the five emergence groups identified in Angola since April 2019. The tree includes cVDPV2 sequences of isolates from DRC (18), Congo (4), and Zambia (1). The five independent cVDPV2 emergences are color-coded. Sequence names start by three-letter country code followed by emergence name, province, and year. Bold circles at interior nodes represent posterior values > 0.7. The scale at the bottom of the tree represents the number of substitutions per site.
Fig. 4.
Fig. 4.
Location of environmental surveillance sites and their annual non-polio enterovirus detection rates, Angola, 2019 and 2020.
Fig. 5.
Fig. 5.
NPAFP and stool adequacy rates by district, Angola, 2019 and 2020.
Fig. 6.
Fig. 6.
Cumulative mOPV2 SIA rounds performed in Angola, by district, 2019–2020.
See this image and copyright information in PMC

References

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