The Effect of Oral Cholera Vaccine in Response to an Outbreak of Cholera in aComplex Emergency, Borno State, Northeast Nigeria.

Background: Cholera Outbreak remains a global health threat amongst Internally Displaced Persons (IDPs) and areas facing complex emergencies. The insurgency in Northeast Nigeria disrupted social services and displaced thousands into IDPs camps which are overcrowded with sub-optimal water, sanitation, and hygiene. We confirmed, characterized the outbreak and instituted control measures which include the first-ever use of Oral Cholera Vaccine (OCV) in Nigeria. Methods: We defined a suspected cholera case-patient as any person above two (≥ 2) years of age presenting with Acute Watery Diarrhea (AWD) and severe dehydration or dying from AWD, with or without vomiting between 14th August to 21st December 2017. We conducted a descriptive and analytic study. Using the Polio vaccination structure, we launched an OCV campaign in two phases (rounds) targeting all people above one (≥ 1) year of age in the affected communities and IDP camps. Results: We identified 6,430 case-patients with 61 deaths in seven (7) Local Government Areas (LGAs) of Borno State which include 3,512 (54.62%) in Jere, 1,870 (29.08%) Monguno, 845 (13.14%) Dikwa, 115 (1.79%) Guzamala, 63 (0.98%) Maiduguri, 23 (0.36%) Mafa and 2 (0.03%) in Gubio. Most of the case-patients 6,109 (95%) were IDPs living in camps. The median age was nine (9) years (Range: 2-80). Females 2,780 (43%) were most affected than males. We targeted a total of 855,492 individuals above one year of age in the affected LGAs for an OCV. We vaccinated 896,919 individuals using 914,565 doses of OCV, giving a coverage rate of 105%. The wastage rate was 0.4%. We did not report any Adverse Events Following Immunization (AEFI). On OCV day four, 122 was the highest number of daily reported case-patients after which the daily case count began to decline until the end of the outbreak. The overall case fatality rate (CFR:0.95%) was 0.95%. Conclusion: The protracted cholera outbreak increased in magnitude and strength, and affected mostly children living in IDPs camps. The cholera outbreak was rapidly detected, and the response was timely, which might have been a possible reason for the low CFR. The reactive OCV might have influenced the ending of the outbreak. Despite the complex and challenging context, we were able to contain the outbreak within four months with a low CFR.