TABLE 1. Characteristics of vaccine effectiveness analysis participants without immunocompromising conditions, including case-patients hospitalized with COVID-19 and controls hospitalized without COVID-19, by mRNA vaccination group — 21 hospitals,* 18 U.S. states, August–December 2021.
| Characteristic | Vaccination group, no./Total no. (%)† |
P-value for comparison of 2-dose versus 3-dose group¶ | ||
|---|---|---|---|---|
| Unvaccinated (n = 1,065) | 2 mRNA vaccine doses (n = 679)† | 3 mRNA vaccine doses§ (n = 131) | ||
|
COVID-19 case-patients
|
744/1,065 (70) |
212/679 (31) |
10/131 (8) |
<0.001 |
|
Age group, yrs
| ||||
| 18–49 |
454/1,065 (43) |
64/679 (9) |
9/131 (7) |
0.31 |
| 50–64 |
327/1,065 (31) |
179/679 (26) |
29/131 (22) |
|
| ≥65 |
284/1,065 (27) |
436/679 (64) |
93/131 (71) |
|
|
Female sex
|
486/1,065 (46) |
329/679 (48) |
67/131 (51) |
0.57 |
|
Race/Ethnicity**
| ||||
| White, non-Hispanic |
566/1,065 (53) |
409/679 (60) |
100/131 (76) |
0.008 |
| Black, non-Hispanic |
220/1,065 (21) |
134/679 (20) |
16/131 (12) |
|
| Any race, Hispanic |
195/1,065 (18) |
85/679 (13) |
10/131 (8) |
|
| Non-Hispanic, all other races |
57/1,065 (5) |
37/679 (5) |
2/131 (2) |
|
| Unknown |
27/1,065 (3) |
14/679 (2) |
3/131 (2) |
|
|
U.S. Census region
| ||||
| Northeast |
176/1,065 (17) |
160/679 (24) |
20/131 (15) |
0.030 |
| Midwest |
215/1,065 (20) |
151/679 (22) |
32/131 (24) |
|
| South |
391/1,065 (37) |
210/679 (31) |
35/131 (27) |
|
| West |
283/1,065 (27) |
158/679 (23) |
44/131 (34) |
|
|
LTCF resident††
|
25/1,004 (2) |
71/663 (11) |
17/120 (14) |
0.27 |
|
Employed
|
343/813 (42) |
104/556 (19) |
23/96 (24) |
0.23 |
| Health care worker |
21/813 (3) |
26/556 (5) |
10/96 (10) |
0.023 |
|
Reported ≥1 previous hospitalization in the last year
|
267/947 (28) |
298/598 (50) |
50/119 (42) |
0.12 |
|
No. of chronic medical condition types (IQR)
|
1 (0–2) |
2 (1–3) |
2 (1–3) |
0.10 |
|
Self-reported previous laboratory-confirmed SARS-CoV-2 infection
|
68/1,063 (6) |
36/679 (5) |
7/131 (5) |
0.98 |
|
Vaccine product received
| ||||
| Pfizer-BioNTech |
NA |
386/679 (57) |
93/131 (71) |
0.001 |
| Moderna |
NA |
288/679 (42) |
35/131 (27) |
|
| Both products |
NA |
5/679 (0.7) |
3/131 (2) |
|
|
Interval between second vaccine dose and illness onset, days, median, (IQR)
|
NA |
225 (203–248) |
257 (240–276) |
<0.001 |
|
Interval between second and third vaccine dose, days, median (IQR)
|
NA |
NA |
230 (211–248) |
NA |
| Interval between third vaccine dose and illness onset, days, median (IQR) | NA | NA | 25 (13–36) | NA |
Abbreviations: LTCF = long-term care facility; NA = not applicable.
* Hospitals by U.S. Census region included Northeast: Baystate Medical Center (Springfield, Massachusetts), Beth Israel Deaconess Medical Center (Boston, Massachusetts), Montefiore Medical Center (New York City borough of the Bronx, New York); Midwest: University of Iowa Hospitals & Clinics (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), The Ohio State University Wexner Medical Center (Columbus, Ohio); South: Vanderbilt University Medical Center (Nashville, Tennessee), University of Miami Medical Center (Miami, Florida), Emory University Hospital (Atlanta, Georgia), The Johns Hopkins Hospital (Baltimore, Maryland), Atrium Health Wake Forest Baptist Medical Center (Winston-Salem, North Carolina), Baylor Scott & White Medical Center (Temple, Texas); West: Stanford University Medical Center (Palo Alto, California), Ronald Reagan 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), University of Washington Medical Center (Seattle, Washington).
† Three vaccination groups were included; unvaccinated patients received no COVID-19 vaccine doses before the date of current illness onset; 2-dose recipients received 2 doses of an mRNA COVID-19 vaccine with the second dose received ≥180 days before the date of illness onset; 3-dose recipients received a third (booster) dose of vaccine with ≥180 days between the second and third dose and ≥7 days between the date of dose 3 receipt and illness onset. Among those who received a third dose with mRNA-1273 from Moderna, one half a dose (0.25 mL) was recommended for the third dose.
§ Dose 3 received ≥6 months after dose 2.
¶ Comparisons were made between 2-dose (primary series only) and 3-dose recipients (booster) groups using Pearson's chi-square testing for categorical variables and the non-parametric Wilcoxon rank-sum test for continuous variables.
** Race and ethnic groups self-reported.
†† LTCFs included residence in a nursing home, assisted living home, or rehab hospital or other subacute or chronic facility before the hospital admission.