A reactive vaccination campaign with single dose oral cholera vaccine (OCV) during a cholera outbreak in Cameroon.

Background: Cameroon chose Oral Cholera Vaccine (OCV) mass vaccination campaign in addition to other interventions to respond to outbreaks since 2015. There is still a persistent controversy on the effectiveness of reactive OCV mass vaccination campaign.

Objective: This article aimed to share evidence-based observations on the effect of a reactive single-dose OCV mass vaccination campaign on cholera cases in Cameroon.

Methods: Health area centered risk analysis was used to identify nine high risk health areas among four health districts in the |North Region as hotspots. About 537,274 people at risk of cholera transmission one year of age and above including pregnant women were eligible to receive OCV. A total of 537,279 doses of OCV was deployed for vaccination from August 1-5, 2019 through door-to-door strategy for urban health districts, and fixed/ temporary fixed posts strategies for rural health districts.

Results: The overall vaccination coverage was 99.9%. Vaccine wastage rate was less than 0.5% (0.0011%). Independent monitoring showed vaccination coverage at 97.2%. The 2019 epidemic curve went down after OCV intervention on the contrary to that in the year 2018 at the same period. After OCV intervention, cholera cases dropped from about 10.5 to 9.3 cases per week at the regional level while at the district level, they dropped from 5.3 to 2.1, 2.2 to 1.7, 0.6 to 0 and 1.7 to 1.5 cases per week respectively for Garoua, Garoua II, Tchollire and Pitoa. Though not statistically significant (p = 1.4, α = 0.05), cases per 1000 population seemed to remain unchanged among OCV zones (0.32/1000) and non-OCV zones (0.31/1000) in 2018 while they increased from 0.37 (OCV zones) to 0.53 (non-0CV zones) cases per 1000 population in 2019.

Conclusion: There might have been a general trend in the reduction of the number of new cases after a reactive single-dose OCV campaign.