Study aim: Evaluation of Immunogenicity and safety of Noora vaccine as a booster. Design: This clinical trial is designed as a hybrid (in the form of two separate trials) in phase 3: ّ First A randomized, double blind clinical trial with two parallel groups and a single center with a sample size of 300 people. Second A multicenter and single arm clinical trial comparing before and after injection of booster vaccine with a sample size of 10000 people. Settings and conduct: The first part in the single center of Shahid Soleimani will be randomly double blind with parallel groups to check the immunogenicity . Blinding ratio will be 1: 2 and the volunteer, researcher and executive staff are unaware of the nature of the injection. The second ward will be in one of the 10 affiliated centers of Baqiyatallah Hospital, before and after. After injection, possible allergic reactions and other reactions will be recorded. Participants/Inclusion and exclusion criteria: Inclusion criteria include: over 18 years of age, candidates who have received two identical doses of the specified approved vaccine by MOH, and at least 3 months after the second dose, fully understand the provisions of the consent form and sign it. Exclusion criteria include: COVID19 infection in the past two months, quarantine, history of certain diseases, medication received in the last 3 months, receiving immunoglobulin or blood products in the previous 3 months, pregnant women Or breastfeeding or intending to pregnancy Intervention groups: Including two intervention groups 1) Injection of 80 μg of recombinant RBD protein vaccine 2) Injection of a placebo dose Main outcome variables: Primary Outcomes: Comparison of antibody levels in a sample of 300 volunteers on days 0 and 21 after injection. Cell immune response to booster dose and measurement of neutralized antibody level in 90 subgroups.