Randomisation and Masking

A contract research organisation was tasked with the generation of the master randomisation code, as well as dispatch and labelling of vaccine vials. The master randomisation code containing randomisation number and intended allocation was uploaded on an interactive web response system. Based on the kit code list, kits were assigned to sites having the kit codes and allocation groups.

At the site level, the system would set the randomisation number and kit allotment without displaying the true group allocation. The same group was allocated for the second visit.

Block randomisation was performed:

Except for an unmasked member of the contract research organization, all others- participants, investigators, study coordinators, study-related personnel, and the funder- were masked to treatment group allocation.

Participants were assigned a computer-generated randomisation code that maintained masking. A masked study nurse was responsible for vaccine preparation and administration and vials were coded to ensure masking. The appearance, colour, and viscosity were identical across all vaccine and control formulations.