Immunology: Vaccines induce similar T cell responses against Omicron as other variants

Spike-protein-specific T cell responses induced by vaccination are well conserved against the Omicron variant, according to data presented in a paper, published in Nature.

Recent studies have indicated that Omicron substantially evades neutralizing antibody responses elicited by current vaccines. However, the effect on vaccine-elicited cellular immune responses (T cell responses) is unclear.

Jinyan Liu, Dan Barouch and colleagues assessed CD8+ and CD4+ T cell responses in 47 individuals in Boston (USA) who had received either one dose of the Johnson & Johnson vaccine (20 participants) or two doses of the Pfizer–BioNTech vaccine (27 participants). None of the participants had previously been infected with SARS-CoV-2 and had negative nucleocapsid antibody responses.

Using intracellular cytokine staining assays, the authors report that, 8 months after vaccination, both types of vaccine induced comparative spike-protein-specific CD8+ and CD4+ T cell responses against the ancestral WA1/2020, Delta and Omicron variants. The data suggests that median Omicron-specific CD8+ T cell responses were 82–84% of WA1/2020-specific responses, and CD4+ T cell responses were 82–100% of WA1/2020-specific responses. By contrast, 5 unvaccinated individuals who had never been infected had negligible spike-specific CD8+ and CD4+ T cell responses.

These findings demonstrate substantial CD8+ and CD4+ T cell cross-reactivity with Omicron, although the authors caution that responses may be different in some individuals. The authors also note that two individuals who received the Pfizer–BioNTech vaccine had undetectable CD8+ T cell responses against Omicron.