question: Rapid ramp up of immune responses against SARS-CoV-2 during pandemic enables adequate prevention and treatment for COVID-19. Estimating levels of SARS-CoV-2 spike protein antibodies post vaccination is crucial for designing mass-vaccination strategies. The aim of this study was to evaluate effectiveness of Sputnik V first dose in Pakistan. A cross-sectional study of 2000 participants was conducted for examining Gam-COVID-Vac or Sputnik V first dose effects at 21st days post administration at Islamabad Diagnostic Center, Islamabad, Pakistan. From 100 real-time PCR negative (SARS-CoV-2 RNA) individuals, samples were collected and analyzed for antibodies to the SARS-CoV-2 spike protein using Electro-chemiluminescence immunoassay (ECLIA) (Elecsys # 09289267190 Roche, USA). 85% of the participants showed strong positive results with SARS-CoV-2 spike protein antibodies > 1.5 AU/ml. The individuals with antibody titer > 250 AU/ml were 34.9%. Among those with antibody levels > 250 AU/ml 52% had previous history of COVID-19 infection. While participants with > 100 AU/ml of antibodies were 12.7%. However 9.5% showed antibody titer of > 25 AU/ml. 27% of participants had antibody titers of > 1.5–2.5 AU/ml. While antibody titers of < 1.5 AU/ml were observed among 15.9% of participants. Majority of the individuals represented significantly high antibody titers against SARS-CoV-2 even before second booster dose of Ad5 based Sputnik V vaccine. Continuous monitoring of antibody levels among COVID-19 vaccinated populations are deemed to assess humoral immunity status against SARS-CoV-2 infections.