Efficacy, safety, and immunogenicity of Soberana recombinant vaccine (product of Finlay Institute) based on RBD protein subunit of Sars-Cov-2 in a 2-dose regimen with and without a booster dose: a double-blind, randomized, placebo-controlled phase III clinical trial in the Iranian population of 18-80 years

Evaluation of efficacy, safety and immunogenicity of recombinant protein vaccine in the prevention of symptomatic infection, severe disease and death due to SARS - CoV-2, in the population aged 18-80 years

In a double blind randomized trial, 24,000 adults, aged between 18 and 80 years old (in 8 cities) will assign to the vaccine and placebo groups (4:1 ratio). The intervention in 6 cities, will be performed with two doses of vaccine and in 2 cities with three doses of vaccine.

This study will be conducted in 8 centers from 7 provinces. During the study, efficacy, safety and immunogenicity of two doses of Soberana 02 vaccine and two doses of Soberana 02 with one dose of Soberana plus will evaluate in comparison with the control group. Researchers and volunteers are not aware of the product prescription for each individuals.

Inclusion informed consent, 18-80 years, male and female, Iranian citizens, healthy adults/adults with controlled underlying diseases, able to comply with schedule, subjects from 8 cities Exclusion Fever or infectious disease (recently),mental diseases, sever allergies, complicated diseases (asthma, hypertension, renal, liver and hart diseases), application of tetanus vaccines (recently), vaccination against SARS-CoV-2, use of immunomodulators, tattoos on arms, participation in COVID-19 vaccine trials, Blood transfusion and its products (recently), Coagulation problems, heavy smoker-First priority groups for vaccination

Cohort 1: 25 µg of RBD-TT, IM, 0 - 28 Cohort 2: 25 µg of RBD-TT, IM, 0 - 28 + a booster dose (Soberana Plus), 56 Placebo groups: Aluminum hydroxide, IM, 0.5 mL, 0 - 28 (& 56 in Cohort 2)

PCR-confirmed of Covid-19 between day 14 and 75 and day 14 and 90 after the last dose, respectively in the 2-dose and the 2-dose+booster regimens.

Due to the small number of volunteers who were above 65 years (as they have had access to COVID-19 vaccine from the national health system), the 10% limit for recruitment of the above 65 years age group was removed from the protocol upon approval of the DSMB. As per the request of the DSMB committee, new sample size is estimated for the cellular immunity assessment. Accordingly, the following fields in the IRCT were updated: - Secondary outcome variable section> description of the third outcome variable> the sample size for cellular immunity assessment is changed to 130 people. - Abstract section > Study Design section: e 10% limit for recruitment of the above 65 years age group is removed.

The random chain will be defined in the system before the start of the study and the list of randomized treatment groups and the corresponding codes will be delivered to the Food and Drug Administration. Random codes and the type of intervention will be assigned to the candidates based on this list, the details of which are given in the following sections. The random chain in this study will be based on the stratified block randomization method. Stratified randomization will be based on studied cities and the randomization unit is individual participants. Random blocks are a common method for constructing and allocating interventions in clinical trials in which the sample size is divided into a number of blocks of a certain size and in each block the ratio of intervention and control groups in the study is observed. Using this method, it is possible to ensure that the ratio of the intervention group to the control is observed at any time during the study. In the present study, the sample size of 24,000 people in 8 study centres (3000 people in each centre) has been determined. Each centre also has 500 codes in excess of the study size to meet the extraordinary needs of the study (for example, the decision to increase the sample size in one of the centres). The size of the blocks is 25. Therefore, for each centre, 3500 codes in 140 random blocks will be considered, in each of which there are 20 intervention codes and 5 control codes. Each intervention or control code has a unique block ID in the form of a UUID, a 1-digit code for the study centre, a block code from 1 to 140 for labeling vial-holding blocks, and a volunteer code. The volunteer code consists of 5 digits, the first digit of which is the code of the study centre and 4 digits after 1 to 3000 and is therefore unique in the study. Random chain construction is done through a program written specifically for this study. Random chain construction will be performed through a randomization program using the Python 3.8.2 programming language, which was written specifically for this study. In this program, first the total sample size, number of centers, block size, number and ratio of interventions as well as the intervention label are defined. The program then calculates the required number of blocks for each center based on its sample size and block size and creates random chains for each block. In summary, in this method, first a list of intervention and control codes in a block will be made by observing the ratio of the groups. The ordering of the indices is done using a random process in which one of the indices is selected at each stage using a uniform distribution, added in the final order and removed from the unselected indices. This process is repeated for each block.

The unique codes of the volunteers are delivered to the preparation group and a label with the volunteer code is inserted on each vial. None of the people working in the preparation department will be in contact with those are involved in the site. Therefore, at the time of delivery of the vial block to the centres, the study colleagues will not be able to distinguish between the drug vial and the placebo. The suspensions in the vaccine and placebo vials are milky white and are similar in color and clarity. Moreover, vaccine and placebo vials are offered in similar appearance, they are inseparable, and packaging and are placed in boxes of 25. Each box will contain the block number and serial numbers of the vaccine/placebo inside. According to this process, participants, vaccinators, researchers, and outcome assessors will be blind. Vaccinators check the unique code information assigned to the candidate with the code on the vaccine/placebo vial before injection. During the study, all consumed vials will be archived and maintained.