Certain COVID-19 Vaccines Induce Robust Cellular Immunity Against Omicron Variant

The highly-mutated SARS-CoV-2 Omicron variant has been shown to cause breakthrough infections among the vaccinated thanks to its ability to evade the virus-killing neutralizing antibodies that the body makes in response to getting vaccinated, commented Dan H. Barouch, MD, Ph.D., in a press statement issued on January 31, 2022.

However, a limited study recently published by researchers at Beth Israel Deaconess Medical Center (BIDMC) in the peer-reviewed journal Nature demonstrated that cellular immunity induced by current COVID-19 vaccines provided robust protection against severe COVID-19 caused by both the Delta and Omicron variants.

Using samples from uninfected individuals who received either the Johnson & Johnson (Janssen) or Pfizer-BioNTech (Comirnaty) vaccines, Barouch and colleagues measured CD8+ T cell and CD4+ T cell responses to the original, Delta, and Omicron strains of the SARS-CoV-2 virus after one month and then again after eight months following final vaccination.

They likewise assessed antibody responses to the variants at one and eight months out.

Consistent with previous reports, the scientists observed minimal cross-reactive Omicron-specific neutralizing antibodies.

In contrast, the team's data suggested that Omicron-specific CD8+ T cell responses were more than 80% cross-reactive with the CD8+ T cell response to the original strain of the virus.

Similarly, more than 80% of Omicron-specific CD4+ T cells demonstrated cross-reactivity, although responses could vary among individuals.

"Our data provide immunological context for the observation that current vaccines still provide robust protection against severe COVID-19 and hospitalization due to the Omicron variant despite substantially reduced neutralizing antibody responses and increased breakthrough infection," commented corresponding author Dr. Barouch, director of the Center for Virology and Vaccine Research at BIDMC, whose team was involved in the development of the Johnson & Johnson vaccine.   

"Given the role of CD8+ T cells in clearance of viral infections, it is likely that cellular immunity contributes substantially to vaccine protection against severe SARS-CoV-2 disease," said Barouch, who is also a professor of medicine at Harvard Medical School and a member of the Ragon Institute of MGH, MIT, and Harvard.

"This may be particularly relevant for Omicron, which dramatically evades neutralizing antibody responses."

This research was funded in part by the National Institutes of Health, Massachusetts Consortium for Pathogen Readiness, Ragon Institute, Musk Foundation, Reproductive Scientist Development Program from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Burroughs Wellcome Fund, and the Biomedical Advanced Research and Development Authority.

The study authors report no other conflicts of interest; however, Barouch is a co-inventor on provisional vaccine patents.

Located in New York, Beth Israel Deaconess Medical Center is a patient care, teaching, and research affiliate of Harvard Medical School. It consistently ranks as a national leader among independent hospitals in National Institutes of Health funding. For more information, visit www.bidmc.org.