Delta does not have the ‘fentanyl’ mutation (K417N/T), which may influence antibody statistics and permanence depending on each particular patient. More on T cells is here:
Convergent Epitope-Specific T Cell Responses
Although mRNA vaccine efficacy against severe COVID-19 remains high, variant emergence and breakthrough infections have changed vaccine policy to include booster immunizations. However, the effect of diverse and repeated antigen exposures on SARS-CoV-2 memory T cells is poorly understood. Here...
doi.org
’....BnT162b2 vaccination elicits potent spike-specific T-cell responses in naive individuals and also triggers the recall T cell response in previously infected individuals, further boosting spike-specific responses but altering their differentiation state. Overall, our study demonstrates the potential of mRNA vaccines to induce, maintain, and shape T cell memory through vaccination and revaccination.’