Table 1.
Frequency of anti-PF4/polyanion IgG in vaccinated individuals
| Vaccine | BNT162b2 | ChAdOx1 nCoV-19 | Total |
|---|---|---|---|
| Total (%) | 143 (50.9) | 138 (49.1) | 281 (100) |
| Age, y (median) | 43 | 45 | 44 |
| Female (%) | 107 (74.8) | 99 (71.7) | 206 (73.3) |
| Postvaccination PF4/polyanion EIA+ (%) | 8 (5.5) | 11 (8.0) | 19 (6.8) |
| SeCo substudy (n, %) | 111 (47.4) | 123 (52.6) | 234 (100) |
| Postvaccination PF4/polyanion EIA+ (%) | 7* (6.3) | 10* (8.1) | 17* (7.3) |
| Baseline samples available | 3 | 6 | 9 |
| Baseline PF4/polyanion EIA+ (%)† | 2 | 4 | 6 |
| AICOVI substudy (n, %) | 32 (68.1) | 15 (31.9) | 47 (100) |
| Postvaccination PF4/polyanion EIA+ (%) | 1 (3.1) | 1 (6.7) | 2 (4.3) |
| Baseline PF4/polyanion EIA+ (%) | 0 (0) | 1 (6.7) | 1 (2.1) |
*
Eight participants who tested positive after vaccination had no available baseline sample (4 with BNT162b2 and 4 with ChAdOx1 nCoV-19).
†
Only participants with positive PF4/polyanion EIA after vaccination who had an available baseline sample before vaccination were tested.