What you need to know

SARS-CoV-2, the virus that causes COVID-19, has evolved several times since the start of the pandemic. Each new variant has the potential to evade the protection of COVID-19 vaccines designed to target previous strains of the virus. To counter this, booster shots tailored to specific variants have been developed.

In a small study supported by the National Institute of Allergy and Infectious Diseases (NIAID), researchers wanted to see whether antibody-producing immune cells, known as memory B cells, could further develop and learn to recognize the new variants after booster shots were administered.

What did the researchers do?

The researchers recruited 54 volunteers, all of whom had received two doses of either the Pfizer or Moderna mRNA vaccine. None of the volunteers had had COVID-19. They were divided into three groups: 39 volunteers received a booster for the Beta and Delta SARS-CoV-2 variants, 8 received a booster for the Omicron variant, and 7 received a booster for the original strain of SARS-CoV-2.

The researchers collected blood samples at the start of the study and in the following weeks at regular intervals for up to 26 weeks. They also collected lymph node and bone marrow samples from selected participants. The samples were used to analyze the types of variants that the memory B cells could recognize after the booster had been given.

What did they learn?

The researchers found that the antibodies produced by the memory B cells for all three groups primarily recognized the original SARS-CoV-2 spike protein. However, new B-cell responses targeted to specific variants were also created. One of the antibodies created by the Omicron-targeted booster was effective against a subvariant of Omicron that emerged after the Omicron booster had been developed.

Why is this research important?

This research shows that targeted COVID-19 booster vaccines create a better immune response against COVID-19 than vaccines targeting the original strain of SARS-CoV-2. As the virus evolves, the creation and distribution of variant-specific boosters can keep us as safe as possible from severe COVID-19.

Where can I go to learn more?

How boosters produce broad protection against COVID-19

• An article in NIH Research Matters offers a detailed account of the study on Omicron booster vaccines.

COVID-19 immune response improves for months after vaccination

• This report in NIH Research Matters describes earlier work from the same researchers on how memory B and T cells contribute to immunity.

Bivalent Boosters Offer Better Protection Against Omicron

• Another NIAID-supported study showed that bivalent boosters (designed to protect against both the original strain of SARS-CoV-2 and the Omicron variant) were more effective than boosters for just the original virus.

Sources

Alsoussi, W. B., Malladi, S. K., Zhou, J. Q., Liu, Z., Ying, B., Kim, W., Schmitz, A. J., Lei, T., Horvath, S. C., Sturtz, A. J., McIntire, K. M., Evavold, B., Han, F., Scheaffer, S. M., Fox, I. F., Mirza, S. F., Parra-Rodriguez, L., Nachbagauer, R., … & Ellebedy, A. H. (2023). SARS-CoV-2 Omicron boosting induces de novo B cell response in humans. Nature, 617, 592-598. https://doi.org/10.1038/s41586-023-06025-4