Table 2. Geometric means of anti–SARS-CoV-2 serum antibody titers and ratios post-vaccination and post-infection by isotype among participants (N = 11) in a nursing home cohort—Georgia, October 2020‒April 2021*,†.
| Time period (days) | Post-infection | Post-vaccination | Ratio post-vaccination to post-infection | ||
|---|---|---|---|---|---|
| No. specimens tested | Geometric mean | No. specimens tested | Geometric mean | ||
| Pan-Ig | |||||
| 0–14 | 5 | 647.9 | 9 | 10181.0 | 15.7 |
| 15–30 | 7 | 2039.4 | 8 | 290111.6 | 142.3 |
| 31–60 | 9 | 4432.9 | 9 | 79175.1 | 17.9 |
| 61–90 | 3 | 4438.9 | 4 | 44136.9 | 9.9 |
| IgG | |||||
| 0–14 | 5 | 885.0 | 9 | 11879.3 | 13.4 |
| 15–30 | 7 | 4295.0 | 8 | 537275.5 | 125.1 |
| 31–60 | 9 | 10156.4 | 9 | 2036648.2 | 200.5 |
| 61–90 | 3 | 6789.3 | 4 | 105524.0 | 15.5 |
| IgA | |||||
| 0–14 | 4 | 198.9 | 3 | 397.6 | 2.0 |
| 15–30 | 7 | 442.2 | 8 | 1663.5 | 3.8 |
| 31–60 | 7 | 390.5 | 9 | 1734.4 | 4.4 |
| 61–90 | 2 | 419.3 | 4 | 672.2 | 1.6 |
| IgM | |||||
| 0–14 | 4 | 324.1 | 3 | 1026.2 | 3.2 |
| 15–30 | 5 | 536.9 | 2 | 400.5 | 0.7 |
| 31–60 | 5 | 702.2 | 3 | 525.1 | 0.7 |
| 61–90 | 2 | 260.0 | 0 | — | — |
* The post-infection period was defined as the time from SARS-CoV-2 diagnosis (by BinaxNOW™ COVID-19 Ag Cards and/or real-time reverse transcription polymerase chain reaction) to receipt of first Pfizer-BioNTech COVID-19 Vaccine dose. The post-vaccination period was defined as the time after receipt of first vaccine dose to the end of the evaluation period.
† Individuals with serum antibody titers below the seroconversion threshold (defined as a signal threshold >1 at the 1:100 dilution for any isotype) were not included in geometric mean and ratio calculations. Geometric means of IgM titers and ratios were not calculated during 61–90 days because all post-vaccination titers were below the limit of detection. Participant G was not included in the post-infection analyses because they did not provide blood specimens during this time period. Participant C was not included in the post-vaccination analyses due to vaccination refusal. This participant’s titers ranged from 2437–16977 for Pan-Ig, 4919–7045 for IgG, and 267–710 for IgA during the 90–150 days post-infection; their IgM titers were below the limit of detection during this time period.