SARS-CoV-2 infection following vaccination – more robust immunity


In a new study, researchers have looked at the primary site of SARS-CoV-2 infection and done T-cell analysis of nasal swab samples (Figure 1). The study has shown that SARS-CoV-2 infection after vaccination may lead to a better induction of nasal-based immunity to COVID-19. These virus-specific T cells have been shown to provide a more robust immunisation to SARS-CoV-2 in patients who have been infected following vaccination when compared to those with only vaccination.

Figure 1: Phenotypic analysis of T cells in nasal secretion. (A) Schematic of experimental design. (B) Frequency of tissue-resident T cells present in PBMCs (n = 8) and nasal secretion (n = 10). Convalescent vaccinees are indicated by a triangle symbol. (C) Frequency of CD4 and CD8 T cells present in PBMCs (n = 14) or nasal cells (n = 10). Convalescent vaccinees are indicated by a triangle. (D) Proportion of naive (CCR7+CD45RA+), central (CCR7+CD45RA−; TCM), effector (CCR7−CD45RA−; TEM) and terminally differentiated (CCR7−CD45RA+; TEMRA) memory CD4+ and CD8+ nasal T cells (n = 10). (E) Proportion of tissue-resident marker (CD69 and CD103) expression on CD8 and CD4 nasal T cells (n = 10) and corresponding representative plots.

The researchers looked analysed the T cell population of 16 people who received two doses of the Pfizer-BioNTech mRNA vaccine who have never been infected with SARS-CoV-2 and compared it to nasal swab samples from another 34 people who had been vaccinated and infected with SARS-CoV-2 following vaccination.

It was found that virus-specific T cells were found to exist mostly in the nose of the group of patients who had the vaccine and SARS-CoV-2 infection following vaccination. Interestingly, this was not observed in patients who had only the vaccine, with only these T cells being found in the blood.

Future research is needed as the sample size is small, but this study unveils some important insights into our understanding of SARS-CoV-2 vaccination and infection.

Journal article: Lim, J., et al., 2022. SARS-CoV-2 breakthrough infection in vaccinees induces virus-specific nasal-resident CD8+ and CD4+ T cells of broad specificity. Journal of Experimental Medicine.

Summary by Stefan Botha

International Union of Immunological SocietiesUniversity of South AfricaInstitute of Infectious Disease and Molecular MedicineElizabeth Glazer Pediatric Aids FoundationStellenbosch University