This is a summary, written by members of the CITF Secretariat, of:

Wong MK, Liu JT, Budylowksi P, Yue FY, Li Z, Rini JM, Carlyle JR, Zia A, Ostrowski M, Martin A. Convergent CDR3 homology amongst Spike-specific antibody responses in convalescent COVID-19 subjects receiving the BNT162b2 vaccine. Clin Immunol. 2022 Apr;237:108963. doi: 10.1016/j.clim.2022.108963. Epub 2022 Mar 5. Erratum in: Clin Immunol. 2023 May 3. doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in Clinical Immunology, found that individuals who were recovering from a SARS-CoV-2 infection and who were then vaccinated with the Pfizer-BioNTech vaccine had high levels of SARS-CoV-2 neutralization. These individuals also generated a similar population of B cells recognizing the SARS-CoV-2 spike protein. This study was led by Dr. Mario Ostrowski (University of Toronto).

B cell phenotypes and a diverse range of B cell receptor sequences were studied in two previously infected COVID-19 subjects who received either one or two doses of Pfizer-BioNTech vaccine. Blood samples were collected at several timepoints following the onset of symptoms leading up to and following vaccination.

Key findings:

  • Increases in viral neutralizing capability and the proportion of spike-specific B cells and memory B cell spike-specific immunoglobin were observed following vaccination in both subjects.
  • There was an expansion of spike-reactive plasmablastDevelops from a B cell and can become a plasma cell that produces antibodies. and IgA-positive B cells following vaccination in both subjects.
  • Spike-specific antibodies induced by vaccination possessed high CDR3 sequence similarity – more than 90% – and were similar to SARS-CoV-2 antibodies published in the publicly available CoV-AbDab database.

With ongoing implementation of timely third and fourth doses to address waning immunity, the authors highlight the need for further studies to assess the diversification of convergent antibody clonotypes and the duration and magnitude of SARS-CoV-2-specific immune memory after each vaccine dose. This information would help inform the control of SARS-CoV-2 and future variants.