A circulating vaccine-derived poliovirus type 2 outbreak in a chronic conflict setting: a descriptive epidemiological study in South Sudan - 2020 to 2021.

BACKGROUND: In this study, we describe the epidemiological profile of an outbreak of the circulating Vaccine Derived Polio Virus type 2 in South Sudan from 2020 to 2021. METHOD: We conducted a retrospective descriptive epidemiological study using data from the national polio/AFP surveillance database, the outbreak investigation reports, and the vaccination coverage survey databases stored at the national level. RESULTS: Between September 2020 and April 2021, 59 cases of the circulating virus were confirmed in the country, with 50 cases in 2020 and 9 cases in 2021. More cases were males (56%) under five (93%). The median age of the cases was 23.4 ± 11.9 months, ranging from 1 to 84 months. All states, with 28 out of the 80 counties, reported at least one case. Most of the cases (44, 75%) were reported from five states, namely Warrap (31%), Western Bahr el Ghazal (12%), Unity (12%), Central Equatoria (10%), and Jonglei (10%). Four counties accounted for 45.8% of the cases; these are Gogrial West with 12 (20%), Jur River with 5 (8.5%), Tonj North with 5 (8.5%), and Juba with 5 (8.5%) cases. The immunization history of the confirmed cases indicated that 14 (24%) of the affected children had never received any doses of oral polio or injectable vaccines either from routine or during supplemental immunization before the onset of paralysis, 17 (28.8%) had received 1 to 2 doses, while 28 (47.5%) had received 3 or more doses (Fig. 4). Two immunization campaigns and a mop-up were conducted with monovalent Oral Polio Vaccine type 2 in response to the outbreak, with administrative coverage of 91.1%, 99.1%, and 97% for the first, second, and mop-up rounds, respectively. CONCLUSION: The emergence of the circulating vaccine-derived poliovirus outbreak in South Sudan was due to low population immunity, highlighting the need to improve the country's routine and polio immunization campaign coverage.

Acute flaccid paralysis surveillance performance from 2011 to 2020 in Jonglei State, South Sudan: progress and challenges encountered.

Introduction: South Sudan reported the last indigenous wild poliovirus (WPV) in 2001 in Unity State, while the country was part of Sudan. In addition, the country reported an imported case of WPV in 2004-2005 and 2008-2009. The WPV circulation in the state was interrupted in 2009 and the last case was reported in Ayod county. The country continues to be at risk of importation of circulating vaccine-derived poliovirus type 2 (cVDPV2). In 2014 and 2020 the country experienced an outbreak of cVDPV2, in which Jonglei state was one of the affected states. Four out of 50 (8%) cVDPV2 cases in 2020 were reported from Jonglei State. The purpose of this study is to review surveillance performance indicators of Jonglei and compare them with the WHO surveillance performance standard and other country´s surveillance performances. Methods: retrospective secondary data analysis was conducted using the Jonglei state Acute Flaccid Paralysis (AFP) surveillance case-based database from 2011 to 2020. The reason for selecting Jonglei is because it is one of the poor performing states and is chronically hit by flood and internal conflicts. Data analyses were carried out using the Microsoft Excel (2016) program, where descriptive analysis frequencies, tables, and graphs were generated. Results: the study revealed that 346 AFP cases were reported in the counties of Jonglei state from 2011 through 2020. Out of 11 counties, 11 (100%) of them have reported suspected AFP cases. Children under five years accounted for 275 (79%) of all cases. The male gender accounted for 175 (51%) of all cases. A total of 249 (72%) had received three or more doses of Oral Polio Vaccine (OPV). Non-Polio Acute Flaccid Paralysis (NPAFP) rate varies from 1.2 in 2014 to 4.4 cases per 100,000 children under 15 years in 2018. The stool adequacy ranges from 58% in 2020 to 100% in 2011. Conclusion: the performance of Jonglei´s AFP surveillance system did not meet the WHO recommended target for both major AFP surveillance indicators (non-polio AFP rate and stool adequacy) during the study period.

The sensitivity of acute flaccid paralysis surveillance - the case of South Sudan: retrospective secondary analysis of AFP surveillance data 2014-2019.

Introduction: South Sudan has made quite impressive progress in interrupting wild poliovirus and maintaining a polio-free status since the last case was reported in 2009. South Sudan introduced different complementary strategies to enhance acute flaccid paralysis (AFP) surveillance. Hence, the objective of this study is to evaluate the sensitivity of the surveillance system using the WHO recommended surveillance standard and highlight the progress and challenges over the years. Methods: we conducted a retrospective, descriptive, quantitative study design and used the available secondary AFP surveillance database. Results: the overall non-polio AFP rate was 6.2/100,000 children under 15 years old in the study period. The stool adequacy was maintained well above the certification level of surveillance. The two main surveillance performance indicators were met at the national level throughout the study period. In contrast, only five out of ten states persistently attained and maintained the two main surveillance performance indicators throughout the study period, while in 2019 all states achieved except for Jonglei state. During the analysis period, no wild poliovirus was isolated except two circulating Vaccine Derived Poliovirus Type 2 (cVDPV2) cases in 2014 and one Immunodeficiency Vaccine Derived Poliovirus Type 2 (iVDPV2) case in 2015. However, on average, three cases were classified as polio compatible with each year of the study. Conclusion: South Sudan met the two key surveillance performance indicators and had a sensitive AFP surveillance system during the period studied. We recommend intensifying surveillance activities in the former conflict-affected states and counties to maintain polio-free status.