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.

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.

Contribution of Auto-Visual AFP Detection and Reporting (AVADAR) on polio surveillance in South Sudan.

Introduction: the last wild polio virus in South Sudan was documented in 2009. Nonetheless, it was one of the last four countries in the WHO African region to be accepted as a polio-free country in June 2020. In line with this, to accelerate the polio-free documentation process, the country has piloted Auto Visual AFP Detection and Reporting (AVADAR) in three counties. This study examined the contribution of the AVADAR surveillance system to the traditional Acute Flaccid Paralysis (AFP) surveillance system to document lessons learnt and best practices. Methods: we performed a retrospective descriptive quantitative study design to analyze secondary AVADAR surveillance data collected from June 2018 to December 2019 and stored at the WHO AVADAR server. Results: the AVADAR community surveillance system has improved the two main AFP surveillance indicators in the piloted counties and made up 86% of the total number of true AFP cases detected in these counties. The completeness and timeliness of weekly zero reporting were 97% and 94%, respectively and maintained above the standard throughout the study, while the two main surveillance indicators in the project area were improved progressively except for the Gogrial West County. In contrast, main surveillance indicators declined in some of the none-AVADAR implementing counties. Conclusion: the AVADAR surveillance system can overcome the logistical and remoteness barriers that can hinder the early detection and reporting of cases due to insecurity, topographical, and communication barrier in rural and hard-to-reach areas to accomplish and sustain the two main surveillance indicators, along with the completeness and timeliness of weekly zero reporting. We recommend extending this application-based surveillance system to other areas with limited resources and similar challenges by incorporating other diseases of public health concern.