Table 3.
Effectiveness of Booster Vaccination With mRNA Vaccine Against SARS-CoV-2 Infection and COVID-19 Caused by the Omicron Variant Among Participants in the Norwegian Mother, Father, and Child Cohort Study and the Senior Cohort, by Sex
| SARS-CoV-2 Infection | Mild COVID-19 | Moderate or Severe COVID-19 | |||||
|---|---|---|---|---|---|---|---|
| Interval From Vaccination, d | Person Time, d | Cases, na | rVEb (95% CI) | Cases, n | rVEb (95% CI) | Cases, n | rVEb (95% CI) |
| Men, n = 33 163 | |||||||
| 2 dosesc | |||||||
| >130 | 153 995 | 1604 | Ref | 669 | Ref | 883 | Ref |
| Booster vaccinationd | |||||||
| 0–6 | 47 266 | 303 | 40.3 (32.3–47.4) | 164 | 20.7 (5.5–33.5) | 124 | 55.4 (46.0–63.2) |
| 7–30 | 358 248 | 3273 | 43.8 (40.2–47.3) | 1876 | 19.9 (12.1–27.0) | 1250 | 62.6 (59.1–65.8) |
| 31–60 | 459 962 | 6107 | 39.5 (35.8–43.0) | 3171 | 22.7 (15.5–29.4) | 2713 | 53.1 (49.1–55.8) |
| 61–90 | 258 004 | 2862 | 35.6 (30.9–39.9) | 1461 | 23.0 (14.5–30.6) | 1304 | 46.2 (40.7–51.2) |
| >90 | 63 762 | 570 | 21.6 (12.5–29.8) | 324 | 3.0 (−13.3 to 16.9) | 232 | 35.2 (23.7–45.0) |
| Women, n = 52 638 | |||||||
| 2 dosesc | |||||||
| >130 | 265 541 | 3291 | Ref | 938 | Ref | 2282 | Ref |
| Booster vaccinationd | |||||||
| 0–6 | 68 019 | 561 | 27.5 (20.6–33.9) | 248 | −15.9 (−33.9 to −.3) | 300 | 43.4 (36.0–49.9) |
| 7–30 | 506 319 | 5233 | 40.2 (37.4–42.8) | 2301 | −0.7 (−9.1 to 7.2) | 2748 | 56.5 (53.9–59.0) |
| 31–60 | 708 214 | 10 217 | 35.9 (33.2–38.5) | 4335 | −3.2 (−11.4 to 4.4) | 5607 | 51.5 (48.9–53.9) |
| 61–90 | 419 060 | 6015 | 31.5 (28.3–34.6) | 2414 | −1.9 (−10.8 to 6.2) | 3472 | 44.7 (41.4–47.8) |
| >90 | 121 547 | 1426 | 25.4 (20.1–30.3) | 618 | −13.0 (−26.6 to −.9) | 772 | 41.1 (35.6–46.1) |
Abbreviations: CI, confidence interval; COVID-19, coronavirus disease 2019; HR, hazard ratio; Ref, reference; rVE, relative vaccine effectiveness; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Includes asymptomatic SARS-CoV-2 infections and SARS-CoV-2 infection not possible to classify according to severity. Thus, the number of cases exceeds the sum of mild, moderate, and severe COVID-19 cases.
rVE = 100% × (1 − HR). HR was estimated using a stratified Cox model with county as strata and calendar time as the underlying time scale. The model was adjusted for prior SARS-CoV-2 infection and age.
The reference category consisted of person-time more than 130 days after the second vaccine dose up until booster vaccination.
Booster vaccination was defined as a third vaccine dose received at least 130 days after the second dose.