Vol. 6, Issue 2, Part A (2024)

Background: Evaluating the decay of SARS-CoV-2 antibodies over time following a booster dose is critical for understanding the longevity and efficacy of COVID-19 immunity. The rate at which antibodies decrease post-booster can vary based on factors like vaccine type, individual health, and age. This study aimed to assess the temporal decay of SARS-CoV-2 antibodies after booster dose administration. 
Methods: This prospective observational study was carried out at the Department of Biochemistry & Molecular Biology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh, from March 2022 to February 2023. The study included 80 adult participants aged 25 to 65, who received their COVID-19 booster dose approximately 6–8 months prior. Participants were selected using purposive sampling. Data analysis was performed using SPSS version 26.0. 
Results: The study found a significant decrease in serum IgG levels when comparing the 6-8 month’s post-booster period to the 3-month measurement, with p-values indicating strong statistical significance (p<0.001). This decline was consistently observed at 6, 7, and 8 months (p<0.05) across various groups, including different genders, infection, and vaccination statuses, age ranges (25-44 and 45-65), all BMI categories, and individuals with comorbidities such as diabetes (DM) and hypertension (HTN). Although all booster types showed a decrease in IgG levels, the decline was not significant for the Moderna vaccine (p>0.05), whereas significant reductions were noted for the other boosters (p<0.05).
Conclusion: After a booster dose, antibody levels, particularly serum IgG, significantly decline within six to eight months compared to three months, irrespective of age, gender, infection status, vaccination status, BMI, diabetes, and hypertension. All booster types showed reduced IgG levels, but the decline with Moderna was insignificant, indicating variability by vaccine type.