Correlation of Sars-Cov-2 IGG Antibody Levels with Viral Load Among Vaccine Breakthrough Infections: A Study From Rawalpindi

Objective: To determine the correlation between SARS-CoV-2 antibody titers and viral load in vaccine breakthrough infections. Study Design: Cross-sectional analytical study. Place and Duration of Study: Department of Virology, Armed Forces Institute of Pathology, Rawalpindi Pakistan, from Nov 2021 to May 2022. Methodology: Three hundred and thirty-seven patients admitted at the Pak Emirates Military Hospital, who had completed the entire course of the inactivated SARS-CoV-2 vaccination and developed COVID-19, at least 14 days from the second dose were selected. Specimens for the viral load of SARS-CoV-2 were taken from posterior nasopharyngeal swabs and serum for anti-Spike antibodies. Viral load in the specimens were estimated using reverse transcriptase polymerase chain reaction. Meanwhile, antibodies level against the SARS-CoV-2 surface spike protein receptor binding domain were assessed using COBAS e411 Electrochemiluminescence. Results: Two hundred and thirty-two (69%) patients were male, while 104(31%) were female. Age, Cycle Threshold value and antibody titers data were normally distributed. Mean age (in years) of participants was 41.83±15.35 (range 18-65). Mean Cycle Threshold value was 23.79±5.49 (range 13.3–35), while mean anti-Spike IgG titers was 165.29±84.62 (range 12–250). Pearson’s correlation coefficient (r) was 0.023 with a 95% CI [-0.08, 0.13] and p-value >0.05, indicating no correlation between Cycle Threshold values and antibody titers. Conclusion: No correlation was found between viral load and anti-spike antibody among patients presenting with breakthrough infections following vaccination with an inactivated vaccine.