To the Editor — Since December 2019, the COVID-19 pandemic has spread from China across the world. As the pandemic continues, 19 vaccines using different technologies have been authorized and are now being used for large vaccination programs worldwide. These vaccines are based on different vaccine platforms (mRNA, recombinant viruses, adjuvanted recombinant proteins and inactivated viruses) that have never been compared in terms of immunogenicity using the same standardized immunological readouts.
