Table 3.
Immune response to heterologous vaccination.
| Prime (n) | Booster (n) | Time interval (weeks) | aSample collection | Assays for antibody titration | Assays for T cell responses | Weakness of study | Reference |
|---|---|---|---|---|---|---|---|
| ChAdOx1 | BNT162b2 (450) | 8–12 weeks | 14-days | pVNA Commercial immunoassays | ELISA to quantify IFN-γ in overnight stimulated heparinized whole blood stimulated with pools of SARS-CoV-2 spike peptides. | No ChAdOx1 prime boost group. No mRNA vaccine prime and ChAdOx1 booster group. | [61] |
| ChAdOx1 (222) | NA | ||||||
| ChAdOx1 | ChAdOx1 (17) | b82 | 0 to 3 days before and 19 to 21 days after boost vaccination | Chemiluminescent immunoassay Bead-Based Multiplex assay Surrogate virus neutralization test | __ | No BNT prime ChAd booster group. Different prime boost intervals between groups. | [63] |
| ChAdOx1 | BNT162b2 (159) | 83 | |||||
| BNT | BNT162b2 (159) | 20 | |||||
| ChAdOx1 | ChAdOx1 (36) | 10–12 Weeks | 20–28 days 20–21 days 27–31 days | Microarray-based immunoassay Surrogate SARS-CoV-2 virus neutralization test. pVNA | ELISA to quantify IFN-γ in heparinized whole blood stimulated with pools of SARS-CoV-2 S1 peptides. | ChAdOx1 prime boost group comparatively smaller. Different intervals between prime and boost vaccination. | [66] |
| ChAdOx1 | BNT162b2 (104) | 10–12 Weeks | |||||
| BNT162b2 | BNT162b2 (159) | 3 weeks | |||||
| ChAdOx1 | ChAdOx1 (32) | 73 days | 16 days 17 days | Spike IgG and IgA, and reciprocal titers of neutralizing antibodies | Flow cytometry to analyze total number of spike-specific cytokine secreting CD4+ and CD8+ T cells. PBMCs were stimulated for 12-16 hours | No BNT prime booster, BNT prime, ChAd booster groups | [67] |
| ChAdOx1 | BNT162b2 (159) | 74 days | |||||
| ChAdOx1 (222) | NA | ||||||
| ChAdOx1 | ChAdOx1 (55) | 9-12 | 9-12 weeks | ELISA Neutralization assay | Flow cytometry to analyze S-specific CD4+ and CD8+ T cells. Heparinized whole blood was stimulated by S overlapping peptides for 6 hours in presence of co-stimulatory antibodies against CD28 and CD49d. | No mRNA vaccine prime and ChAd group | [68] |
| c mRNA vaccine | mRNA vaccine (64) | 3-6 | 3-6 weeks | ||||
| ChAdOx1 | mRNA vaccine (97) | 9-12 | 9-12 weeks | ||||
| ChAdOx1 | BNT162b2 (2) | 33 days | 13 days | ELISA pVNA | __ | N is very small and no ChAdOx1 prime-boost, BNT162b2 prime boost, and BNT162b2 prime covishield booster groups. | [69] |
| ChAdOx1 | ChAdOx1 (25) | 28 days | Authentic virus neutralization assay pVNA | IFN-γ ELISpot specific to SARS-CoV-2 spike peptides, analyzed on PBMCs | [71] | ||
| ChAdOx1 | BNT162b2 (24) | ||||||
| BNT162b2 | BNT162b2 (26) | ||||||
| BNT162b2 | ChAdOx1 (25) |
aTime points are related to evaluation of humoral or cellular immune responses post second dose. ChAdOx1 represents ChAdOx1 nCoV-19. NA = not applicable. bmedian (interquartile range, IQR) days. cmRNA-vaccinees included either BNT162b2 or mRNA-1273 vaccinees. pVNA = pseudovirus neutralization assay. PBMCs = peripheral blood mononuclear cells, S = spike protein.