Booster doses increase protection against COVID-19 variants

A study by Monash immunologists suggests that booster vaccine doses
elicit memory B cells with higher affinity to COVID-19, enabling
recognition of VoC. L-R: First author PhD student Gemma Hartley and.
senior author Prof Menno van Zelm

by Gemma Hartley, PhD student

COVID-19 vaccines have been rolled out across the world with great success. However, variants of concern (VoC) now challenge the protection that these vaccines provide. 

Third and fourth dose boosters are known to increase protection against VoC, but the immunological basis of this is still unclear.

A multi-institutional study between Monash University, Alfred Health and the Burnet Institute studied the response to first and second dose Pfizer mRNA vaccination in 30 healthy adults. Blood samples were taken pre-vaccination and 3-4 weeks after the first and second dose. All donors generated antibodies to the vaccine, as well as resting memory B cells, an important marker for long term immunity. 

Importantly, we show that the second vaccine dose not only increases the number of memory B cells but also the fraction of those that bind the Gamma and Delta VoC. Therefore, additional doses of vaccine can further increase the recognition to VoC and provide better protection.

While the Gamma and Delta variants are no longer circulating in the community, this concept still stands: booster doses increase protection against the current Omicron subvariants. 

We propose that this is through memory B cells increasing their affinity to the vaccine and therefore being able to better recognize Omicron. 

In ongoing work on both COVID-19 and H1N1 influenza viruses, we are studying the effects of third and fourth dose boosters on the recognition of Omicron variants, as well as the capacity of annual influenza vaccinations to elicit memory B cell responses for protection against the changeable H1N1 strain.

 Reference (Department of Immunology and Pathology affiliated authors are bolded)

Gemma E. Hartley, Emily S.J. Edwards, Nirupama Varese, Irene Boo, Pei M. Aui, Scott J. Bornheimer, P. Mark Hogarth, Heidi E. Drummer, Robyn E. O’Hehir, Menno C. van Zelm. Double-dose mRNA vaccination to SARS-CoV-2 progressively increases recognition of variants-of-concern by Spike RBD-specific memory B cells. bioRxiv 2022.08.03.502703; doi: https://doi.org/10.1101/2022.08.03.502703 This article is a preprint and has not been certified by peer review