Sinopharm and Sinovac COVID-19 vaccines; Prevalence and risk factors for post full vaccination weak immunity.

Objective: To see the prevalence and risk factors for post full vaccination (Sinopharm and Sinovac COVID-19 vaccines) weak immunity in persons with no history of viral exposure. Study Design: Prospective Observational. Setting: Syed Research Centre, Sialkot. Period: Nov 2021 to Feb 2022. Material & Methods: Eighty two individuals (male/female, aged: 24-70 years) were enrolled from District Sialkot (Pakistan). Two doses of Sinopharm or Sinovac COVID-19 vaccine were administered to each participant before blood sampling. The quantity of COVID-19 spike immunoglobulin G against SARS-CoV-2 (5-Antigen) was detected in serum using chemiluminescence immunoassay technique [threshold titer: 7.1 (detection), 105. 63 (seroprotection), 492.96 BAU/mL (strong humoral response)]. Results: Overall, 96.3% seropositivity, 89% seroprotection, and 37.8% (n = 31) weak immune response were recorded. Whereas, mean antibody titer was found to be 2312.02 (range: 0.0 – 28711.74) BAU/mL. A vaccinated male had approximately 4 folds (95%CI: 1.297 – 11.504; p = .002) more likelihood of weak immune response than females. Similarly, the rate of poor immunological outcome was higher in individuals with >24.9 Kg/m2 (69.2%, n = 27) body mass index compared to ≤24.9 Kg/m2. A person with Sinopharm COVID-19 vaccine was more vulnerable to weak immune response than Sinovac vaccinated participants (RR = 2.351; 95%CI = 1.327 – 4.167; p .002; 57.6% vs. 24.5%, respectively). Co-occurrence of age (>47 years) and BMI (>24.9 Kg/m2) existed in 11 of 28 males (39.3%) with impaired immunogenicity. Conclusion: The high rate of post full vaccination weak immune response is alarming. Gender, BMI, and vaccine type were amongst the predictors for diminished humoral response.