Impact Study of Cholera Vaccination in Endemic Areas - Seroprevalence

The project will comprise three different components:

Clinical cholera surveillance to measure cholera diseases incidence in selected African hotspots targeted by vaccination.

Serial serological surveys to measure the prevalence of recent cholera infection (within the last 12 months).

Identification and follow up of individuals with positive V. cholerae shedding (symptomatic or asymptomatic) among sero-survey participants and among household members of cholera confirmed cases.

The present protocol relates to the setup of seroprevalence surveys and the follow up of individuals with positive V. cholerae shedding identified through seroprevalence surveys, in DRC.

This protocol will allow us to assess if a large vaccination campaign reaching high coverage in cholera hotspot in Africa can allow sustained control of cholera for at least two years, by fulfilling the following specific objectives:

• To calculate the proportion of individuals infected with cholera recently (i.e. previous year or last 2 months) before the campaign distribution or in non-vaccinated zones (baseline survey, rural site) or following the mass OCV campaign and before the start of the usual cholera season (pre-season survey, urban site).
• To assess proportion of individuals recently infected (i.e. infected in the last two months or in the last year) during the expected peak-week of cholera in the area (peak survey, urban site) and at the end of the expected cholera season (post-season survey), as compared to baseline or pre-season survey.
• To assess the intra-household transmission and correlation in cholera recent infections among vaccinated and non-vaccinated households (post-season survey)
• To compare mortality linked to diarrheal diseases and potential cholera in the community of rural site before and after vaccination
• To assess the duration of shedding among vaccinated and unvaccinated individuals and the duration of viable V. cholerae in the peri-household environment.
• To measure the secondary cholera attack rates (symptomatic and asymptomatic) at household level among vaccinated and unvaccinated individuals following the identification of an index case in a given household.

Inclusion criteria

• All persons,

• Living in the randomly-selected households in targeted area AND
• Randomly selected among household members. Inclusions will be limited to 1 participant per household, except for one survey AND
• Giving his/her consent (or assent for children 13 to 17 years old) to participate in the study

Exclusion criteria

• People who decline to participate will be excluded from the study. For 2nd survey in Goma only: members of the household who cannot be reached after 2 attempts will be excluded.