Inactivated SARS-CoV-2 vaccine (Vero cell)(Wuhan Institute of Biological Products Co., Ltd.)

This is a randomized, phase II trial which will be conducted among volunteers aged 18 years and above in Karachi, Lahore and Islamabad, Pakistan. The trial will have nine arms and is an open label study. Trained persons will administer the vaccine and draw blood under strict aseptic measures. The immune responses using pseudo neutralizing antibodies against SARS-CoV-2 in COVID-19 seronegative participants receiving heterologous and homologous COVID-19 vaccines will be assessed. Anti-spike IgG antibodies by ELISA and pseudo neutralizing antibodies against SARS-CoV-2 will also be measured. The safety and reactogenicity will also be assessed by recording serious adverse events (SAE), adverse events of special interest (AESI), solicited local and systemic reactions and medically attended adverse reactions through biochemical and hematological tests or safety measures throughout the study. In most cases the adverse events are mild and self-limiting but can require medication and/or hospitalization in rare cases. Participants suffering from any adverse event causally related to the to the trial intervention will be facilitated and the cost of treatment including laboratory investigations will be provided to them. Data confidentiality will be ensured by delinking names in forms and through password protection.