A study in a tertiary level hospital in Bangladesh shows no age dependent variations in COVID-19 antibody level among school-aged children and healthy adults

Background: The immune response to COVID-19 varies among individuals based on multiple factors, including age, comorbidities and prior exposure to the virus. Understanding these variations is crucial for optimizing vaccination strategies and public health policies. This study was conducted in a tertiary-level hospital in Bangladesh to assess whether age influences COVID-19 antibody levels among school-aged children and healthy adults. Methods: This cross-sectional observational study was conducted at Central Police Hospital, Dhaka, Bangladesh, between September 2022 and August 2024. Data were collected from two groups: children aged 3-15 years attending the Paediatric Outpatient Department and adults aged 25-76 years attending the Medicine Outpatient Department for routine medical visits. A total of 94 children and 112 adults were included in the study. All statistical analyses were conducted using statistical software SPSS version 26.0. Results: The mean total antibody levels ranged from 94±14.6 in children aged 3-5 years to 98±15.1 in adults aged 41-60 years, with no significant difference across age groups (p=0.827). Regression analysis showed that age was not a significant predictor of antibody levels (β₁=0.015, p=0.252). Comorbidities in adults, including diabetes (96±15.1, p=0.612), hypertension (95±13.8, p=0.529) and heart disease (93±16.5, p=0.451), did not significantly affect antibody responses. Conclusions: This study found that school-aged children exhibited significant COVID-19 antibody levels despite neither being vaccinated nor having a documented history of infection. In contrast, healthy adults achieved comparable antibody levels primarily through vaccination. Regression analysis confirmed that age was not a significant predictor of antibody levels and comorbidities did not have a notable impact on antibody responses in adults. These findings suggest that children may acquire antibodies through alternative mechanisms, such as asymptomatic exposure or passive immunity, while adults rely on vaccination for immune protection.