Volume 28, Number 10—October 2022
Research Letter
Effectiveness of Booster and Influenza Vaccines against COVID-19 among Healthcare Workers, Taiwan
Table
Characteristics of 2,196 healthcare workers tested for SARS-CoV-2 after receiving COVID-19 booster and influenza vaccines, Taipei Tzu Chi Hospital, Taipei, Taiwan*
| Characteristics | Regular testing, n = 343† |
Symptom-triggered testing, n = 1,853 |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Positive, no. (%) | Negative, no. (%) | p value | OR (95% CI) | Positive, no. (%) | Negative or no symptom, no. (%) | p value | OR (95% CI) | ||
| Total |
93 (100) |
250 (100) |
NA |
NA |
360 (100) |
1,493 (100) |
NA |
NA |
|
| Sex | 0.051 | 0.084 | |||||||
| F | 67 (72.0) | 205 (82.0) | NA | 1.4 (0.7–3.1) | 278 (77.2) | 1,085 (72.7) | NA | 1.0 (0.7–1.4) | |
| M |
26 (28.0) |
45 (18.0) |
NA |
Referent |
82 (22.8) |
408 (27.3) |
NA |
Referent |
|
| Age range, y | 0.377 | 0.345 | |||||||
| 71–80 | 1 (1.1) | 0 | NA | NA | 1 (0.3) | 8 (0.5) | NA | 0.7 (0.1–6.0) | |
| 61–70 | 1 (1.1) | 4 (1.6) | NA | 0.7 (0.1–6.6) | 6 (1.7) | 55 (3.7) | NA | 0.5 (0.2–1.3) | |
| 51–60 | 3 (3.2) | 18 (7.2) | NA | 0.5 (0.1–2.0) | 33 (9.2) | 160 (10.7) | NA | 0.9 (0.6–1.3) | |
| 41–50 | 15 (16.1) | 39 (15.6) | NA | 0.9 (0.4–1.9) | 93 (25.8) | 362 (24.2) | NA | 1.0 (0.7–1.4) | |
| 31–40 | 29 (31.2) | 63 (25.2) | NA | 1.1 (0.6–2.1) | 92 (25.6) | 391 (26.2) | NA | 1.0 (0.7–1.3) | |
| 21–30 |
44 (47.3) |
126 (50.4) |
NA |
Referent |
135 (37.5) |
517 (34.6) |
NA |
Referent |
|
| Work sector | <0.001 | <0.001 | |||||||
| Nursing | 52 (55.9) | 175 (70.0) | NA | 0.1 (0.1–0.4) | 170 (47.2) | 641 (42.9) | NA | 0.9 (0.6–1.2) | |
| Medical | 15 (11.3) | 37 (14.8) | NA | 0.2 (0.1–0.5) | 39 (10.8) | 309 (20.7) | NA | 0.5 (0.3–0.8) | |
| Technical | 6 (6.5) | 9 (3.6) | NA | 0.3 (0.1–1.1) | 43 (11.9) | 197 (13.2) | NA | 0.8 (0.5–1.2) | |
| Laboratory, pharmacy | 3 (3.2) | 20 (8.0) | NA | 0.1 (0.0–0.3) | 32 (8.9) | 100 (6.7) | NA | 1.1 (0.7–1.8) | |
| Housekeeping | 0 | 2 (0.8) | NA | NA | 6 (1.7) | 9 (0.6) | NA | 2.8 (0.9–8.6) | |
| Administration |
17 (18.3) |
7 (2.8) |
NA |
Referent |
70 (19.4) |
237 (15.9) |
NA |
Referent |
|
| No. COVID-19 vaccine doses | 0.065 | <0.001 | |||||||
| 3 | 88 (94.6) | 246 (98.4) | NA | 0.2 (0.0–0.8) | 319 (88.6) | 1,416 (94.8) | NA | 0.4 (0.2–0.6) | |
| 2 | 5 (5.4) | 4 (1.6) | NA | Referent | 38 (10.6) | 73 (4.9) | NA | Referent | |
| 1 | 0 | 0 | NA | NA | 0 | 0 | NA | NA | |
| 0 |
0 |
0 |
NA |
NA |
3 (0.8) |
4 (0.3) |
NA |
NA |
|
| COVID-19 primary series‡ | 0.442 | 0.348 | |||||||
| Viral vector + viral vector | 70 (75.3) | 193 (77.2) | NA | NA | 270 (75.0) | 1,091 (73.1) | NA | NA | |
| Viral vector + mRNA | 7 (7.5) | 27 (10.8) | NA | NA | 45 (12.5) | 189 (12.7) | NA | NA | |
| mRNA + mRNA | 15 (16.1) | 30 (12.0) | NA | NA | 41 (11.4) | 206 (13.8) | NA | NA | |
| Protein subunit + protein subunit |
0 |
0 |
NA |
NA |
0 |
2 (0.1) |
NA |
NA |
|
| COVID-19 booster§ | 1.00 | 0.145 | |||||||
| mRNA | 86 (92.5) | 243 (97.2) | NA | NA | 317 (88.1) | 1,387 (92.9) | NA | NA | |
| Protein subunit |
0 |
2 (0.8) |
NA |
NA |
2 (0.5) |
27 (1.8) |
NA |
NA |
|
| Booster vaccine date¶ | 0.111 | <0.001 | |||||||
| December 2021 | 23 (24.7) | 68 (27.2) | NA | NA | 70 (19.4) | 319 (21.4) | NA | NA | |
| January 2022 | 55 (59.1) | 164 (65.6) | NA | NA | 219 (60.8) | 999 (66.9) | NA | NA | |
| February 2022 | 4 (4.3) | 4 (1.6) | NA | NA | 17 (4.7) | 35 (2.3) | NA | NA | |
| March 2022 | 3 (3.2) | 7 (2.8) | NA | NA | 5 (1.4) | 32 (2.1) | NA | NA | |
| April 2022 | 0 | 3 (1.2) | NA | NA | 6 (1.7) | 24 (1.6) | NA | NA | |
| May 2022 |
1 (1.1) |
0 |
NA |
NA |
0 |
4 (0.3) |
NA |
NA |
|
| Tetravalent influenza vaccine, 2021–22 season | 0.297 | 0.016 | |||||||
| Vaccinated | 68 (73.1) | 167 (66.8) | NA | 1.5 (0.8–2.7) | 265 (73.6) | 1,001 (67.0) | NA | 1.5 (1.1–2.0) | |
| Not vaccinated | 25 (26.9) | 83 (33.2) | NA | Referent | 95 (26.4) | 492 (33.0) | NA | Referent | |
*p values calculated by using χ2 test; OR and 95% CI calculated by using multinomial logistic regression. NA, not applicable; OR, odds ratio. †For age 71–80 y and housekeepers of the regularly tested subgroup, estimates were not shown because the groups were too small. ‡Excluding 7 unvaccinated workers and 3 workers who did not report vaccine type. Data available for a total of 2,186 healthcare workers; regular testing subgroup included 92 positive cases and 250 negative cases; symptom-triggered testing subgroup included 356 positive cases and 1,488 negative cases; thus, percentages do not add up to 100%. §Excluding 7 unvaccinated workers, 120 workers who did not receive a booster vaccine, and 5 workers who did not report booster vaccine type. Data available for a total of 2,064 healthcare workers; regular testing subgroup included 86 positive cases and 245 negative cases; symptom-triggered testing subgroup included 319 positive cases and 1,414 negative cases; thus, percentages do not add up to 100%. ¶Excluding 7 unvaccinated workers, 120 workers who did not receive a booster vaccine, and 7 workers who did not report month of booster vaccine. Data available for a total of 2,062 healthcare workers; regular testing subgroup included 86 positive cases and 246 negative cases; symptom-triggered testing subgroup included 317 positive cases and 1,413 negative cases; thus, percentages do not add up to 100%.