COVID-19 mRNA booster vaccine induces transient CD8+ T effector cell responses while conserving the memory pool for subsequent reactivation

Abstract

Immunization with two mRNA vaccine doses elicits robust spike-specific CD8+ T cell responses, but reports of waning immunity after COVID-19 vaccination prompt the introduction of booster vaccination campaigns. However, the effect of mRNA booster vaccination on the spike-specific CD8+ T cell response remains unclear. Here we show that spike-specific CD8+ T cells are activated and expanded in all analyzed individuals receiving the 3rd and 4th mRNA vaccine shots. This CD8+ T cell boost response is followed by a contraction phase and lasts only for about 30-60 days. The spike-specific CD8+ T memory stem cell pool is not affected by the 3rd vaccination. Both 4th vaccination and breakthrough infections with Delta and Omicron rapidly reactivate CD8+ T memory cells. In contrast, neutralizing antibody responses display little boost effect towards Omicron. Thus, COVID-19 mRNA booster vaccination elicits a transient T effector cell response while long-term spike-specific CD8+ T cell immunity is conserved to mount robust memory recall targeting emerging variants of concern.

Innate and adaptive immune response in SARS-CoV-2 infection-Current perspectives

“…It’s worth noting that memory CD8 + T cells found in a study of UK convalescent individuals following COVID-19 would support an understanding of protective immunity and may contribute to put forward potential immune-based therapeutics ( 100 ). Vaccine-induced CD8 + T cells also help to fight against SARS-CoV-2 re-infection ( 101 – 103 ). One week after prime vaccination with BNT162b2, a stable and fully functional CD8 + T cell response was mobilized, as indicated by the increased production of IFN-γ and TNF-α ( 104 ).…”

Hybrid and herd immunity 6 months after SARS-CoV-2 exposure among individuals from a community treatment program

“…Recent evidence from Reinscheid et al also revealed that the spike-specific CD8 + T memory stem cell pool is not affected by the third dose of a vaccine. Moreover, the booster dose of a vaccine and breakthrough infections with Delta or Omicron variants of SARS-CoV-2 rapidly reactivated CD8 + T memory cells 3 months after the previous vaccination dose 12 .…”

Effect of vaccine booster, vaccine type, and hybrid immunity on humoral and cellular immunity against SARS-CoV-2 ancestral strain and Omicron variant sublineages BA.2 and BA.5 among older adults with comorbidities: a cross sectional study

“…Previous study suggest that the CD8+ T cell response after booster doses was transient and lasted for less than 2 months. 29 Since the blood specimens were collected at a median of over 120 days after the booster dose in our study, we would have missed the phase with the transient increase in T cell response. Since T cell is crucial for limiting disease severity, future research on vaccine boosters should explore strategies which can improve T cell response.…”