Table 2. Primary Immunogenicity Analysis of Ancestral SARS-CoV-2 (D614G) and Omicron after 50 μg of mRNA-1273.214 or mRNA-1273 as a Second Booster Dose in Participants with No Previous SARS-CoV-2 Infection.*.
| Variable | Ancestral SARS-CoV-2 (D614G) | Omicron | ||
|---|---|---|---|---|
| 50-μg mRNA-1273.214 (N=334) |
50-μg mRNA-1273 (N=260) |
50-μg mRNA-1273.214 (N=334) |
50-μg mRNA-1273 (N=260) |
|
| Before booster | ||||
| No. of participants evaluated† | 334 | 260 | 334 | 260 |
| Observed geometric mean titer (95% CI)‡ | 1266.7 (1120.2 to 1432.5) |
1521.0 (1352.8 to 1710.2) |
298.1 (258.8 to 343.5) |
332.0 (282.0 to 390.9) |
| Day 29 | ||||
| No. of participants evaluated† | 334 | 260 | 334 | 260 |
| Observed geometric mean titer (95% CI)‡ | 5977.3 (5321.9 to 6713.3) |
5649.3 (5056.8 to 6311.2) |
2372.4 (2070.6 to 2718.2) |
1473.5 (1270.8 to 1708.4) |
| Factor change in geometric mean titer (95% CI)‡ | 4.7 (4.4 to 5.1) | 3.7 (3.4 to 4.0) | 8.0 (7.2 to 8.8) | 4.4 (4.0 to 5.0) |
| Estimated geometric mean titer (95% CI)§ | 6422.3 (5990.1 to 6885.7) |
5286.6 (4887.1 to 5718.9) |
2479.9 (2264.5 to 2715.8) |
1421.2 (1283.0 to 1574.4) |
| Geometric mean titer ratio (97.5% CI)§ | 1.22 (1.08 to 1.37) | — | 1.75 (1.49 to 2.04)¶ | — |
| Seroresponse at day 29‖ | ||||
| No. of participants/total no. | 334/334 | 260/260 | 333/333 | 256/258 |
| Percentage of participants (95% CI) | 100 (98.9 to 100) | 100 (98.6 to 100) | 100 (98.9 to 100) | 99.2 (97.2 to 99.9) |
| Difference (97.5% CI) — percentage points** | 0 | — | 1.5 (−1.1 to 4.0)†† | — |
Antibody values assessed by means of pseudovirus neutralizing antibody assay that were reported as being below the lower limit of quantification (LLOQ; 18.5 for ancestral SARS-CoV-2 [D614G] and 19.9 for omicron) were replaced by 0.5 times the LLOQ. Values greater than the upper limit of quantification (ULOQ; 45,118 for ancestral SARS-CoV-2 [D614G] and 15,502.7 for omicron) were replaced by the ULOQ if actual values were not available. Included are participants with no previous SARS-CoV-2 infection (primary analysis set).
Shown is the number of participants with nonmissing data at the time point (at or after baseline).
The 95% confidence intervals were calculated on the basis of the t-distribution of log-transformed values or difference in the log-transformed values for geometric mean titer and factor change in geometric mean titer, respectively, then back-transformed to the original scale.
Log-transformed antibody levels were analyzed with the use of an analysis of covariance model, with the study vaccine as a fixed effect and with adjustment for age group (<65 or ≥65 years) and prebooster titers. The resulting least-squares means and 95% confidence intervals, and the difference in least-squares means and 97.5% confidence intervals, were back-transformed to the original scale.
The value exceeded noninferiority criteria and met superiority criteria, including meeting noninferiority criteria for the three primary objectives in the prespecified hypothesis testing sequence and the superiority criterion of a lower boundary of the confidence interval for the geometric mean titer ratio greater than 1.
Seroresponse at a participant level was defined as a change from below the LLOQ to at least 4 times the LLOQ, or an increase by a factor of at least four if the baseline value was greater than or equal to the LLOQ; the comparison was with the prevaccination baseline value. Percentages were based on the number of participants with nonmissing data at baseline and the corresponding time point; 95% confidence intervals were calculated with the use of the Clopper–Pearson method.
The difference in the percentage of participants with a seroresponse is a calculated common risk difference that uses inverse-variance stratum weights and the middle point of Miettinen–Nurminen confidence limits of each one of the stratum risk differences. The stratified Miettinen–Nurminen estimate and the confidence interval cannot be calculated when the percentage of participants with a seroresponse in both groups is 100%; the absolute difference is reported.
The 97.5% confidence interval was calculated by means of a stratified Miettinen–Nurminen method, with adjustment according to age group.