Table 1. Baseline Characteristics of Persons in the Study.*.
| Variable | Total Eligible for Inclusion in Four-Dose Group (N=258,994) |
Four-Dose Group (N=182,122) |
Control Group (N=182,122) |
|---|---|---|---|
| Median age (IQR) — yr | 73 (67–79) | 72 (67–78) | 72 (67–78) |
| Age group | |||
| 60–69 yr | 90,701 (35) | 67,778 (37) | 67,778 (37) |
| 70–79 yr | 107,620 (42) | 76,630 (42) | 76,630 (42) |
| ≥80 yr | 60,673 (23) | 37,714 (21) | 37,714 (21) |
| Sex | |||
| Female | 133,282 (51) | 97,113 (53) | 97,113 (53) |
| Male | 125,712 (49) | 85,009 (47) | 85,009 (47) |
| Population sector | |||
| General Jewish | 243,651 (94) | 173,689 (95) | 173,689 (95) |
| Arab | 9,178 (4) | 4,828 (3) | 4,828 (3) |
| Ultra-Orthodox Jewish | 6,165 (2) | 3,605 (2) | 3,605 (2) |
| No. of hospital admissions in previous 3 yr | |||
| 0 | 184,499 (71) | 140,226 (77) | 140,226 (77) |
| 1 | 44,502 (17) | 27,612 (15) | 27,612 (15) |
| 2 | 16,295 (6) | 8,310 (5) | 8,310 (5) |
| 3 or 4 | 10,116 (4) | 4,692 (3) | 4,692 (3) |
| ≥5 | 3,582 (1) | 1,282 (1) | 1,282 (1) |
| No. of CDC-defined risk factors for severe Covid-19 | |||
| 0 | 43,408 (17) | 31,533 (17) | 31,533 (17) |
| 1 | 59,304 (23) | 42,236 (23) | 42,236 (23) |
| 2 | 58,992 (23) | 40,275 (22) | 40,275 (22) |
| ≥3 | 97,290 (38) | 68,078 (37) | 68,078 (37) |
| CDC risk factors | |||
| Cancer | 14,123 (5) | 9,228 (5) | 8,665 (5) |
| Chronic kidney disease | 47,529 (18) | 32,343 (18) | 32,999 (18) |
| Chronic obstructive pulmonary disease | 15,882 (6) | 10,919 (6) | 11,675 (6) |
| Heart disease | 61,521 (24) | 41,018 (23) | 40,270 (22) |
| Solid-organ transplantation | 250 (<1) | 171 (<1) | 174 (<1) |
| Obesity† | 68,436 (26) | 48,949 (27) | 48,818 (27) |
| Severe obesity† | 4,911 (2) | 3,548 (2) | 3,877 (2) |
| Sickle cell disease | 14 (<1) | 4 (<1) | 8 (<1) |
| Smoking | 27,962 (11) | 20,224 (11) | 24,904 (14) |
| Type 2 diabetes mellitus | 84,137 (32) | 59,936 (33) | 60,138 (33) |
| Possible CDC risk factors | |||
| Asthma | 18,193 (7) | 12,806 (7) | 12,609 (7) |
| Cerebrovascular disease | 27,902 (11) | 18,319 (10) | 19,447 (11) |
| Other respiratory disease | 3,170 (1) | 2,232 (1) | 2,202 (1) |
| Hypertension | 148,096 (57) | 103,260 (57) | 101,536 (56) |
| Immunosuppression | 16,214 (6) | 11,304 (6) | 10,890 (6) |
| Neurologic disease | 31,546 (12) | 21,295 (12) | 22,793 (13) |
| Liver disease | 8,889 (3) | 6,221 (3) | 6,657 (4) |
| Overweight† | 109,322 (42) | 76,447 (42) | 75,086 (41) |
| Thalassemia | 1,061 (<1) | 732 (<1) | 821 (<1) |
| Type 1 diabetes mellitus | 2,393 (1) | 1,614 (1) | 1,432 (1) |
*
Persons 60 years of age or older with no previous confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who had received a fourth vaccine dose (four-dose group) were matched with those who had received only a third dose given at least 4 months earlier (control group). CDC denotes Centers for Disease Control and Prevention, and IQR interquartile range.
†
Overweight was defined as a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of 25 to <30, obesity as a BMI of 30 to <40, and severe obesity as a BMI of 40 or greater.