Table 3 Seroresponse rates by pseudovirus nAb (ID50; D614G) assay: phase 2 after booster compared to the phase 3 COVE primary series (per-protocol immunogenicity set)

From: Immune response to SARS-CoV-2 after a booster of mRNA-1273: an open-label phase 2 trial

Statistic

Seroresponse rate per assay-specific definitiona

Seroresponse rate per four-fold definitionb

Seroresponse rate per four-fold rise from baseline definitionc

Phase 2 part B, 50-µg boosterd (n = 295)

Phase 3 COVE, 100 µg, primary series (n = 1,055)

Phase 2 part B, 50-µg boosterd (n = 295)

Phase 3 COVE, 100-µg, primary series (n = 1,055)

Phase 2 part B, 50-µg boostere (n = 294)

Phase 2 part A, after dose 2 of primary series (n = 294)

N1

294

1,050

294

1,050

289

289

Participants achieving seroresponse, n (seroresponse rate %)

275 (93.5)

1,038 (98.9)

265 (90.1)

1,033 (98.4)

289 (100.0)

284 (98.3)

95% CIf

90.1, 96.1

98.0, 99.4

86.1, 93.3

97.4, 99.1

98.7, 100.0

96.0, 99.4

Difference in seroresponse rateg (phase 2 part B versus phase 3 COVE) (%)

−5.3

−8.2

1.7

95% CIh

−8.8, −2.9

−12.2, −5.2

0.4, 4.0

  1. N1, number of participants with non-missing data at both post-baseline time point of interest and baseline.
  2. For participants who received the primary series in phase 3 COVE, seroresponse was defined based on the fold rise at day 57 (28 days after the second dose of mRNA-1273) compared to the baseline titer (before the first dose of the primary dose).
  3. aSeroresponse specific to the ID50 titer in the D614G pseudovirus nAb assay at a participant level was defined as a change from below the LLOQ to equal to or above the LLOQ or at least a 3.3-fold rise if the baseline was equal to or above the LLOQ.
  4. bSeroresponse at participant level was defined as a change of titer in the D614G pseudovirus nAb assay from below the LLOQ to equal to or above 4× LLOQ or a four times or higher ratio in participants with titers above the LLOQ.
  5. cSeroresponse at participant level was defined as a change of titer in the D614G pseudovirus nAb assay from below the LLOQ at baseline (before Dose 1) to equal to or above 4× LLOQ or a four times or higher ratio in participants with titers above the LLOQ at baseline (before Dose 1).
  6. dFor participants who received a booster vaccination in phase 2 part B, seroresponse was defined based on the fold rise at OL-D29 (28 days after the booster dose of mRNA-1273) compared to the pre-booster titer (OL-D1; at least 6 months after completion of the primary series).
  7. eFor participants who received a booster vaccination in phase 2 part B, seroresponse was defined based on the fold rise at OL-D29 (28 days after the booster dose of mRNA-1273) compared to the baseline titer (before the first dose of the primary dose).
  8. f95% CI was calculated using the Clopper–Pearson method.
  9. gFor the four-fold rise from baseline definition, the difference in seroresponse rate was the fold rise in phase 2 part B at OL-D29 (28 days after the booster dose of mRNA-1273) compared to 28 days after the second dose during the primary series in phase 2 part A.
  10. h95% CI was calculated using the Miettinen–Nurminen (score) confidence limits.
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