Table 1.
Characteristics of the studies included in the systematic review.
| First Name | Year | Country | Study Design | Sample Size (n) | Mean Age (y) | Female (%) | Type of Vaccine | Proportion Primary Course of Vaccination (%) | Proportion First Booster Dose (%) | Proportion Second Booster Dose (%) | Time Since Last Dose (d) | Proportion of Prior Infections (%) | Mean Protective Antibody Titer | Prevalent VOC | Type of Serologic Testing |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Atef S. et al. [18] | 2023 | UAE | Longitudinal | 940 | 35.5 | 0.0 | Inactivated-mRNA | 97.7 | 75.5 | 2.1 | 89.2 | 12.2 | Anti-RBD 941.7 (652.4) | Delta | CMIA |
| Dimeglio C. et al. [19] | 2022 | France | Longitudinal | 259 | 40.1 | 74.5 | mRNA-VV | 100.0 | 36.7 | 0.0 | 208.4 | 64.9 | <6000 BAU/mL provided no protection against Omicron BA.1 infection; 6000–20,000 BAU/mL provided 55.6% protection;20,000 or more provided 87.7% protection | Omicron | ECLIA |
| Fernández-Rivas G. et al. [20] | 2022 | Spain | Cross-Sectional | 5000 | 35–54 (44.9) | 80.4 | mRNA | 87.4 | NA | NA | 180.0 | 16.6 | Anti-Spike 1268.8 (1197.6) | Delta | ECLIA |
| Fong Y. et al. [21] | 2022 | Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa and USA | Case-cohort | 826 | 49.4 | 45.2 | VV | 100 | 0.0 | 0.0 | 29.0 | 0.0 | Breakthrough case 27.54 BAU/mL vs. non-case 32.49 BAU/mL | pre-Delta | ECLIA |
| Fong Y. et al. [22] | 2023 | USA | Case-cohort | 639 | 55 | 46.2 | Recombinant protein subunit | 100.0 | NA | NA | 35.0 | NA | Anti-RBD 2123.0 (2998.6)- Anti-Spike 1552.0 (1973.3) |
pre-Delta | ECLIA |
| Gilbert P.B. et al. [23] | 2022 | USA | Case-cohort | 1147 | 54.4 | 47.0 | mRNA | 100.0 | 0.0 | 0.0 | 30.0 | 0.0 | spike IgG of 33, 300, and 4000 BAU/mL, vaccine efficacy was 85% (31 to 92%), 90% (77 to 94%), and 94% (91 to 96%) | pre-Delta | ECLIA |
| Gilboa M. et al. [24] | 2023 | Israel | Longitudinal | 2310 | 50.0 | 76.6 | mRNA | 100.0 | 100.0 | 0.0 | NA | 0.0 | IgG > 2000 BAU were less likely to be infected compared to IgG ≤ 500 BAU (OR, 0.52; 95% CI, 0.39–0.67) | Omicron | CMIA |
| Goldblatt D. et al. [25] | 2021 | UK–Latvia–South Africa | Cross-Sectional | 122 | 46.5 | 60.7 | mRNA-VV | 100.0 | NA | NA | 15.4 | 0.0 | Overall protective threshold was estimated to be 154 BAU/mL (95% CI 42–559) | pre-Delta. Delta | ECLIA |
| Hertz T. et al. [26] | 2023 | Israel | Longitudinal | 607 | 47.3 | 72.0 | mRNA | 100.0 | 100.0 | 39.9 | 147.4 | 0.0 | IgG responses against the RBD were not significantly associated with infection status (four doses: p = 0.083; three doses p = 0.281) | Omicron | ELISA |
| Macrae K. et al. [27] | 2022 | Canada | Longitudinal | 140 | 54.6 | 67.1 | mRNA-VV | 90.0 | 56.4 | NA | 112.3 | NA | Average antibody concentration prior to infection was 1911.3 BAU/mL | Delta–Omicron | ELISA |
| Marking U. et al. [8] | 2023 | Sweden | Longitudinal | 347 | 52.6 | 89.0 | mRNA-VV | 100.0 | 100.0 | 0.0 | 34.4 | 42.0 | Adjusted relative risk of infection for participants above vs. below 75th percentile of serum-IgG was 0.35 (95% CI 0.14–0.71) | Omicron | ECLIA |
| Möhlendick B. et al. [28] | 2022 | Germany | Longitudinal | 1391 | 40.7 | 77.3 | mRNA-VV | 100.0 | 100.0 | 0.0 | NA | NA | After 1 month following booster dose administration subjects with 3477.0 BAU/mL became infected, while with 4733.0 BAU/mL did not | Delta–Omicron | CMIA |
| Perez-Saez J. et al. [29] | 2023 | Switzerland | Longitudinal | 1083 | 18–64 (91.0) | 54.5 | mRNA | NA | NA | NA | NA | 31.4 | Overall three-fold reduction in the hazard of reporting a positive test for antibody levels above 800 IU/mL | Omicron | ECLIA |
| Regenhardt E. et al. [30] | 2023 | Germany | Longitudinal | 81 | 34.9 | 69.1 | mRNA-VV | 100.0 | 40.7 | 0.0 | NA | NA | Median anti-RBD-IgG before Omicron breakthrough infection = 1235, 95% CI [771–2404] vs. Delta breakthrough infection = 138, 95% CI [106–220] | Delta–Omicron | CMIA |
| Regev-Yochay, G. et al. [31] | 2023 | Israel | Longitudinal | 1461 | 41.7 | 54.1 | mRNA | 96.4 | 0.0 | 0.0 | 177.8 | 22.8 | Uninfected 168.2 BAU per mL [95% CI 158.3–178.7] vs. infected 130.5 BAU/mL [118.3–143.8] | Delta | CMIA |
| Roy A. et al. [32] | 2023 | France | Longitudinal | 636 | 37.0 | 74.2 | mRNA-VV | 100.0 | 38.1 | 0.7 | 120.2 | 17.1 | 1040.8 (1188.3) | Delta–Omicron | CMIA |
| Sendi P. et al. [33] | 2023 | Switzerland | Longitudinal | 949 | 41.0 | 27.0 | mRNA | 89.0 | 69.5 | 0.0 | NA | 54.9 | association of anti-S1 IgG levels and protection from infection was higher during the Omicron period | Delta–Omicron | ELISA |
| Wei J. et al. [34] | 2022 | UK | Longitudinal | 222,493 | 56.0 | 53.8 | mRNA-VV | 100.0 | 0.0 | 0.0 | 71–76 | 9.7 | ChAdOx1 or BNT162b2 required estimated levels of 107 BAU/mL and 94 BAU/mL, respectively |
Delta | ELISA |
Abbreviations: mRNA—Messenger Ribonucleic Acid Vaccine; VV—Viral Vector Vaccines; CMIA—Chemiluminescent Microparticle Immunoassay; ECLIA—Electrochemiluminescence Immunoassay; ELISA—Enzyme Linked Immunosorbent Assay.