The Epidemiology unit of the Ministry of Health of Sri Lanka has planned to conduct a survey to determine the level of COVID-19 specific immunity among adults in the community. The Health operations pillar of the WHE, unity desk of the WHO headquarters and the WHO Country Office for Sri Lanka jointly reviewed the proposal for the proposed survey. They also provided technical support to Sri Lanka to align the seroprevalence survey proposal with the Unity Studies: WHO sero-epidemiological investigations protocol.
The proposed study is proven to be rational given the changed epidemiological situation of COVID-19 from intermittent cases to clusters and widespread transmission in the country with surges due to SARS CoV 2 variants, especially the Delta variant of concern by July 2021. In addition to the natural immunity, the population immunity was also rapidly being built up as a result of the roll-out of the COVID-19 vaccination programme in the country. The COVID-19 immunization campaign was started from 28 January 2021. The campaign was launched with different types of COVID-19 vaccines.
The study aims to determine the population level immunity against SARS-CoV-2 virus through measuring seroprevalence of SARS-CoV-2 specific antibodies in adults. It is anticipated that findings of the proposed study will help the government take relevant programme related decisions to implement measures to protect people against COVID-19.
Objectives of the seroprevalence study
- To measure seroprevalence of SARS-CoV-2 antibodies in the population of Sri Lanka by age and sex.
- To estimate the fraction of asymptomatic or subclinical infections in the population and by sex and age groups.
- To determine risk factors for infection by comparing the exposure of infected and non-infected individuals for COVID-19 infection in the study population.
The study design is a population based descriptive cross-sectional study. The study will use cluster sampling technique. The clusters to enroll the required sample size will be selected from nine districts. These districts will be Colombo (including Colombo Municipal Council), Gampaha, Nuwara Eliya, Galle, Kandy, Anuradhapura, Kalmunai, Jaffna and Kegalle. Health care staff for the study as study subjects will also be selected from the same districts.
The findings would help identify population immunity gaps for necessary interventions in terms of controlling transmission of SARS-CoV-2 in susceptible populations. The seroprevalence estimate would help the country identify the true burden of infection in the community due to symptomatic and asymptomatic disease as well as the population immunity acquired due to COVID-19 vaccines.