TABLE 2. Effectiveness of COVID-19 mRNA vaccines against COVID-19–associated invasive mechanical ventilation or in-hospital death — 21 hospitals, 18 states,*,† March 2021–January 2022.
| Group/Characteristic | No. of vaccinated case-patients with IMV or death/total no. of case-patients (%) | No. of vaccinated control-patients/ total no. of control-patients (%) | Vaccine effectiveness, % (95% CI) |
|---|---|---|---|
|
All variant periods§
|
307/1,440 (21.3) |
4,020/6,104 (65.9) |
90 (88–91) |
|
No. of mRNA vaccine doses received
| |||
| 2 |
277/1,410 (19.6) |
3,488/5,572 (62.6) |
88 (86–90) |
| 14–150 days after dose 2 |
92/1,225 (7.5) |
2,039/4,123 (49.5) |
92 (90–94) |
| >150 days after dose 2 |
185/1,318 (14.0) |
1,449/3,533 (41.0) |
84 (80–87) |
| 3 |
30/1,163 (2.6) |
532/2,616 (20.3) |
94 (91–96) |
|
Age group, yrs
| |||
| 18–64 |
115/931 (12.4) |
1,807/3,326 (54.3) |
91 (89–93) |
| ≥65 |
192/509 (37.7) |
2,213/2,778 (79.7) |
88 (84–90) |
|
Health status
| |||
| Immunocompromised |
123/232 (53.0) |
1,090/1,504 (72.5) |
74 (64–81) |
| Immunocompetent |
184/1,208 (15.2) |
2,930/4,600 (63.7) |
92 (91–94) |
|
No. of chronic conditions among immunocompetent
| |||
| None |
12/368 (3.3) |
322/642 (50.2) |
98 (97–99) |
| 1 |
34/337 (10.1) |
647/1,094 (59.1) |
95 (92–96) |
| 2 |
60/264 (22.7) |
886/1,320 (67.1) |
89 (85–93) |
| ≥3 |
78/239 (32.6) |
1,075/1,544 (69.6) |
84 (78–89) |
|
Variant period,¶ no. of doses
| |||
|
Pre-Delta, 2 doses
|
13/259 (5.0) |
893/1,738 (51.4) |
95 (90–97) |
|
Delta, 2 or 3 doses
|
235/1,027 (22.9) |
2,741/3,865 (70.9) |
89 (87–91) |
| 2 doses, median = 159 days after dose 2 |
218/1,010 (21.6) |
2,402/3,526 (68.1) |
88 (86–90) |
| 3 doses, median = 35 days after dose 3 |
17/809 (2.1) |
339/1,463 (23.2) |
95 (91–97) |
|
Omicron, 2 or 3 doses
|
59/154 (38.3) |
386/501 (77.0) |
86 (79–91) |
| 2 doses, median = 256 days after dose 2 |
46/141 (32.6) |
193/308 (62.7) |
79 (66–87) |
| 3 doses, median = 60 days after dose 3 | 13/108 (12.0) | 193/308 (62.7) | 94 (88–97) |
Abbreviations: IMV = invasive mechanical ventilation; VE = vaccine effectiveness.
* Reported VE results are for 2 or 3 vaccine doses except where otherwise noted. VE was estimated using logistic regression comparing the odds of being vaccinated with 2 or 3 doses of an mRNA vaccine versus being unvaccinated for laboratory-confirmed cases with IMV or death and test-negative controls and calculated as VE = 100 × (1 − odds ratio). Logistic regression models were adjusted for date of hospital admission (biweekly intervals), U.S. Department of Health and Human Services region of hospital (10 regions), age group (18–49, 50–64, and ≥65 years), sex, and race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic of any race, non-Hispanic other, or unknown). Age-specific models were adjusted for age as a continuous variable.
† Hospitals (cities, states) included Baystate Medical Center (Springfield, Massachusetts), Beth Israel Deaconess Medical Center (Boston, Massachusetts), Montefiore Medical Center (Bronx, New York), Vanderbilt University Medical Center (Nashville, Tennessee), University of Miami Medical Center (Miami, Florida), Emory University Medical Center (Atlanta, Georgia), Johns Hopkins Hospital (Baltimore, Maryland), Wake Forest University Baptist Medical Center (Winston-Salem, North Carolina), Baylor Scott & White Health (Temple, Texas), University of Iowa Hospitals (Iowa City, Iowa), University of Michigan Hospital (Ann Arbor, Michigan), Hennepin County Medical Center (Minneapolis, Minnesota), Barnes-Jewish Hospital (St. Louis, Missouri), Cleveland Clinic (Cleveland, Ohio), Ohio State University Wexner Medical Center (Columbus, Ohio), Stanford University Medical Center (Stanford, California), UCLA Medical Center (Los Angeles, California), UCHealth University of Colorado Hospital (Aurora, Colorado), Oregon Health & Science University Hospital (Portland, Oregon), Intermountain Medical Center (Murray, Utah), and University of Washington (Seattle, Washington).
§ With vaccination defined as receipt of either 2 or 3 mRNA vaccine doses.
¶ Variant periods were defined by hospital admission dates as the following: pre-Delta (when the Alpha variant dominated but other variants co-circulated), March 11–July 3, 2021; Delta, July 4–December 25, 2021, and Omicron, December 26, 2021–January 24, 2022. Start dates for variant periods were selected based on calendar weeks during which the variant accounted for >50% of sequenced viruses that had lineage determination from whole-genome sequencing.