ABSTRACT
The rapid development of vaccines to prevent infection by SARS-CoV-2 virus causing COVID-19
makes necessary to compare the capacity of the different vaccines in terms of development of
a protective humoral response. Here, we have used a highly sensitive and reliable flow
cytometry method to measure the titers of antibodies of the IgG1 isotype in blood of volunteers
after receiving one or two doses of the vaccines being administered in Spain. We took advantage
of the multiplexed capacity of the method to measure simultaneously the reactivity of
antibodies with the S protein of the original strain Wuhan-1 and the variant B.1.1.7 (Alpha). We
found significant differences in the titer of anti-S antibodies produced after a first dose of the
vaccines ChAdOx1 nCov-19/AstraZeneca, mRNA-1273/Moderna, BNT162b2/Pfizer-BioNTech
and Ad26.COV.S/Janssen. Most important, we found a relative reduction in the reactivity of the
sera with the B.1.1.7 versus the Wuhan-1 variant after the second boosting immunization. These
data allow to make a comparison of different vaccines in terms of anti-S antibody generation
and cast doubts about the convenience of repeatedly immunizing with the same S protein
sequence.
https://www.medrxiv.org/content/10.1101/2021.08.12.21261952v1
