Table 2. Linear mixed effects modeling parameter estimates of IgG antibodies to SARS-CoV-2 spike (full length spike, S) and neutralizing antibodies in nursing home residents—Georgia, December 2020– July 2022.
| Groups | Anti-Spike IgG | Neutralizing Antibodies | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of observations | No. of participants | Estimate (log10) | Standard Error | likelihood ratio p-value* | peak (BAU/ml) | % decline/month | No. of observations | No. of participants | Estimate (log10) | Standard Error | likelihood ratio p-value* | peak (% spike) | slope (%/month) | |
| 2 spike exposures † | ||||||||||||||
| Hybrid Immunity‡ | 23 | 17 | -0.39 | 0.11 | 0.02 | 3470.90 | -59.08 | 23 | 17 | 5.70 | 6.90 | 0.16 | 74.77 | 5.70 |
| Vaccine-induced§ | 44 | 7 | 0.29 | 0.11 | 857.96 | -19.58 | 41 | 7 | -9.87 | 7.04 | 58.66 | -4.17 | ||
| 3 spike exposures † | ||||||||||||||
| Hybrid Immunity | 154 | 31 | -0.11 | 0.01 | 0.12 | 5487.64 | -22.64 | 160 | 31 | -6.18 | 1.02 | 0.42 | 99.17 | -6.18 |
| Vaccine-induced | 12 | 5 | -0.05 | 0.03 | 9394.72 | -31.24 | 12 | 5 | -2.77 | 3.43 | 95.21 | -8.95 | ||
| Hybrid Immunity ‡ : 3 vs. 4 spike exposures † | ||||||||||||||
| 3 exposures | 154 | 31 | -0.11 | 0.01 | 0.82 | 5489.91 | -22.54 | 160 | 31 | -6.17 | 0.92 | 0.06 | 99.17 | -6.17 |
| 4 exposures | 60 | 24 | 0.00 | 0.01 | 6292.06 | -23.13 | 60 | 24 | 2.94 | 1.58 | 96.63 | -3.23 | ||
| Hybrid Immunity ‡ : 4 spike exposures versus 5 Spike exposures † | ||||||||||||||
| 4 exposures | 60 | 24 | -0.11 | 0.01 | 0.39 | 6308.83 | -22.71 | 60 | 24 | -3.62 | 0.93 | 0.57 | 96.83 | -3.62 |
| 5 exposures | 17 | 9 | -0.04 | 0.04 | 11519.51 | -29.05 | 16 | 9 | 1.37 | 2.45 | 98.36 | -2.25 | ||
| Hybrid Immunity‡ with 3 Spike Exposures† | ||||||||||||||
| By Sex | ||||||||||||||
| Females | 82 | 15 | -0.11 | 0.01 | 0.91 | 4043.25 | -22.43 | 83 | 15 | -6.42 | 1.45 | 0.80 | 95.85 | -6.42 |
| Males | 72 | 16 | 0.00 | 0.02 | 7298.42 | -22.73 | 77 | 16 | 0.51 | 2.05 | 102.19 | -5.91 | ||
| By mRNA COVID-19 Vaccine | ||||||||||||||
| Moderna | 32 | 8 | -0.12 | 0.02 | 0.46 | 11296.63 | -24.27 | 38 | 8 | -4.28 | 1.92 | 0.24 | 100.58 | -4.28 |
| Pfizer | 122 | 23 | 0.01 | 0.02 | 4271.96 | -21.93 | 122 | 23 | -2.62 | 2.24 | 98.70 | -6.90 | ||
| By Race | ||||||||||||||
| Black | 50 | 11 | -0.10 | 0.01 | 0.13 | 10708.88 | -19.80 | 51 | 11 | -3.92 | 1.74 | 0.12 | 103.26 | -3.92 |
| White | 104 | 20 | -0.02 | 0.02 | 3803.69 | -24.15 | 109 | 20 | -3.30 | 2.10 | 96.89 | -7.22 | ||
| By Immunocompromised Status¶ | ||||||||||||||
| No | 79 | 14 | -0.10 | 0.01 | 0.20 | 4410.80 | -20.96 | 79 | 14 | -6.53 | 1.49 | 0.75 | 98.08 | -6.53 |
| Yes | 75 | 17 | -0.02 | 0.01 | 6710.36 | -24.40 | 81 | 17 | 0.64 | 2.05 | 100.05 | -5.89 | ||
*p-values of <0.006 were considered statistically significant
†Spike exposure is defined as exposure to the viral spike protein due to either a SARS-CoV-2 infection(s) or a dose(s) of an mRNA COVID-19 vaccine receipt. The primary series was considered as two spike exposures. Please refer to S1 Table for further explanation
‡Hybrid immunity was defined as the immune protection in individuals who have had one or more doses of an mRNA COVID-19 vaccine and have evidence of at least one SARS-CoV-2 infection before or after vaccination initiation.
§Vaccine-induced immunity was defined as the immune protection in individuals who have had one or more doses of an mRNA COVID-19 vaccine and remained infection-naive before or after vaccination initiation.
¶A moderate or severely immunocompromising condition included the following: recent or active malignancy, bone marrow transplant, solid organ transplant, primary or secondary immune deficiency, or the use of oral or intravenous steroids for more than a month or any immunosuppressant drugs