Figure 1.

Defining the features of protective T cell immunity

(A) Distinct antigenic histories generate differing levels of T cell memory targeting various viral targets. To date all approved vaccines have relied solely on Spike antigens, generating only Spike-specific memory. In most convalescent individuals, Spike responses are a significant minority of the repertoire but are further expanded by vaccine boosters.

(B) Immunodominance hierarchies have been defined for CD4⁺ and CD8⁺ T cell responses with some epitopes being targeted by up to 10% of CD4⁺ or CD8⁺ compartment. The consequences of differential epitope targeting remain to be defined.

(C) The spectrum of T cell specificity and magnitude generated in convalescent and vaccinated individuals may be driving variation in clinical outcomes, but rigorous correlates of protection of the T cell response have yet to be reported.

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