As part of the clinical trial network being set up by National Biopharma Mission (NBM)-Biotechnology Industry Research Assistance Council (BIRAC), four existing demographc surveillance sites (also referred to as Demographic Health Surveillance sites-DHS)/Health and Demographic Surveillance Sites-HDSS) /Demographic, Developmental and Environmental Surveillance Sites-DDESS) were selected to study epidemiology of Dengue & Chikungunya in different age-groups over a period of three years. This study design involved identification of lab confirmed cases of dengue/ chikungunya through active febrile illness (AFI) surveillance; and three rounds of sero-surveys in a cohort of 1500 individuals (2-50 years) at each site. Serum samples collected in this study would be stored in a centralised bio-repository for exploration of various aetiologies of AFI if required. These sites were expected to undertake community based trials for indigenous dengue/chikungunya vaccines in future.

In view of the COVID-19 pandemic, it was decided that these sites with established community presence and experience of maintaining population cohorts could be leveraged to fill knowledge gaps related to the actual burden of COVID disease in the community as well as to improve understanding of the community transmission dynamics. A fifth site from Pune district of Maharashtra was added for COVID specific research objectives to ensure representation from the Western part of the country.

While a cohort design with active febrile illness (AFI) surveillance appears to be the most comprehensive study design, it is associated with numerous operational challenges at this point of time:

The sample size required to generate a reasonable estimate of incidence of COVID would be high (>5000)

The feasibility of collecting NP swabs / saliva samples for COVID-19 confirmation in community settings is challenging, resource intensive, associated with risk of stigma, community push back and risk to staff. 

The follow-up protocol for any positive case identified is operationally difficult to follow as part of this study.

In view of this, an approach involving follow up of a defined population cohort through repeated serological surveys and syndromic acute febrile illness/Influenza like illness surveillance through fortnightly phone calls  (without lab confirmation) to record suspected cases of COVID-19 was considered to be the most feasible study design operationally and scientifically. With 6-8 vaccine projects being supported by the National Biopharma Mission, BIRAC, data from these sites will be useful in decisions related to selection of vaccine trial sites. Also, when actual vaccine introduction takes place, the information on burden of these syndromes will be useful to plan logistics for required investigations in these cases.

Though the pandemic in India was largely restricted to metros and urban cities in the first few months, it has now reached rural areas as well due to the mass exodus of migrant workers. The selected sites represent a mix of rural and urban population and present an opportunity to estimate burden in both the settings.

To align with the original mandate with which BIRAC had selected these sites, two rounds of serological testing of dengue and chikungunya is proposed to be done in the same cohort to estimate the burden of these diseases in the community. The original protocol prepared for the study on Dengue and Chikungunya epidemiology study shall be implemented after the COVID pandemic subsides.