Serosurveillance of COVID 19 among unvaccinated children aged 10-17 in Sikkim, North-Eastern India: A cross-sectional analysis

Abstract

Introduction: Serological studies offer valuable insights into the burden of diseases, especially among vulnerable populations. This preliminary serological survey for COVID19 was conducted among unvaccinated children aged 10-17 years in both urban and rural areas of East Sikkim, India, following the second wave of the pandemic. Conducting the study after the peak of transmission was deemed appropriate for a one-time cross-sectional investigation, to assess the prevalence of COVID19 in the region.

Methods: This cross-sectional study was conducted in 10 randomly selected urban areas and 9 rural areas within Gangtok Municipal Corporation. The survey team consisted of an accredited social health activist (ASHA), an anganwadi worker, and a laboratory technician. They conducted a household survey by randomly selecting households and obtaining informed consent from guardians. Demographic information was recorded, and blood samples were collected from participants. Antibody levels were estimated using the Cobas-e411 equipment and Roche’s Elecsys Anti-SARS-CoV-2 immunoassay reagent, which detects both IgM and IgG antibodies in human serum/plasma.

Results: A total of 1,104 participants were enrolled in the study. The overall seroprevalence rate was 58.24% (n=643), with urban areas contributing 39.24% (n=433) and rural areas contributing 19% (n=210). Seroprevalence did not significantly differ between genders, with 56.27% (n=269) of males and 59.74% (n=374) of females testing positive for SARS-CoV-2 antibodies. A significant difference was observed between symptomatic and asymptomatic participants, with seroprevalence rates of 71.25% and 57.22%, respectively, indicating higher antibody prevalence in symptomatic individuals. Among the seropositive participants, only 9% were symptomatic, while 91% were asymptomatic. The case-to-infection ratio (CIR) was 1:8, and the case fatality rate was zero for children aged 10-17 in this region.

Conclusions: Although seroprevalence has been increasing nationally, a portion of the population remains seronegative. The case-to-infection ratio suggests that many infections go undetected or unreported. This data highlights that the actual number of COVID19 infections was significantly higher than the number of confirmed cases reported by testing. Continued monitoring and targeted public health measures are essential to address the COVID19.