Subjects will be enrolled in the study if they meet all the following criteria. <br/ >1. Male and female aged â?¥ 18 years <br/ >2. Subject who had recieved primary vaccination (both doses completed) with either <br/ >a. COVAXIN (Group 1) OR <br/ >b. COVISHIELD (Group 2) <br/ >Where last dose of primary vaccination was taken 6-7 months prior to the screening visit <br/ >3. Subjects who are determined by medical/surgical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study <br/ >4. If the subject had COVID-19 after primary vaccination, that subject should have passed 3 months after being asymptomatic or RT-PCR negative <br/ >5. Negative COVID-19 Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) test result at the screening visit <br/ >6. Consent for using effective methods of contraception during the entire trial and 3 months after its completion <br/ >7. No evidence of pronounced vaccine-induced reactions or complications after receiving immunobiological products in medical history <br/ >8. No acute infectious and/or respiratory diseases within at least 14 days before the enrollment <br/ >

Subjects will be enrolled in the study if they meet all the following criteria. <br/ >1. Male and female aged â?¥ 18 years <br/ >2. Subject who had recieved primary vaccination (both doses completed) with either <br/ >a. COVAXIN (Group 1) OR <br/ >b. COVISHIELD (Group 2) <br/ >Where last dose of primary vaccination was taken 6-7 months prior to the screening visit <br/ >3. Subjects who are determined by medical/surgical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study <br/ >4. If the subject had COVID-19 after primary vaccination, that subject should have passed 3 months after being asymptomatic or RT-PCR negative <br/ >5. Negative COVID-19 Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) test result at the screening visit <br/ >6. Consent for using effective methods of contraception during the entire trial and 3 months after its completion <br/ >7. No evidence of pronounced vaccine-induced reactions or complications after receiving immunobiological products in medical history <br/ >8. No acute infectious and/or respiratory diseases within at least 14 days before the enrollment <br/ >