Table 1.
Descriptive Characteristics, Vaccination History, and 2009 A(H1N1) Pandemic Influenza Virus Hemagglutination Inhibition Antibody Seroresponse of Healthcare Personnel
| Characteristic | Preseason | After 2010–2011 TIV | End-of-Season |
|---|---|---|---|
| Serum (n = 1417) | Serum (n = 865) | Serum (n = 1254) | |
| Descriptive characteristics | |||
| Demographics | |||
| Age, y | 42 (12) | 43 (12) | 42 (12) |
| Age group | |||
| 18–34 y | 523 (37%) | 279 (32%) | 442 (35%) |
| 35–49 y | 508 (36%) | 300 (35%) | 449 (36%) |
| 50–65 y | 386 (27%) | 286 (33%) | 363 (29%) |
| Female | 1132 (80%) | 712 (82%) | 1011 (81%) |
| White | 1117 (79%) | 696 (80%) | 988 (79%) |
| Hispanic | 165 (12%) | 99 (11%) | 144 (11%) |
| Health | |||
| Body mass index, kg/m2 | 28 (7) | 29 (7) | 28 (7) |
| Subjective health status (1–5) | 4.1 (0.7) | 4.1 (0.7) | 4.1 (0.7) |
| HCP with high-risk condition(s) in 2009–2010 | 477 (34%) | 316 (37%) | 431 (34%) |
| Proxies for exposure to infection | |||
| HCP with ≥1 MAARI during A(H1N1)pdm09 | 176 (12%) | 106 (12%) | 164 (13%) |
| HCP with ≥1 MAARI during 2010–2011 influenza season | 141 (10%) | 89 (10%) | 126 (10%) |
| Household size | 2.1 (1.6) | 2.1 (1.5) | 2.1 (1.5) |
| Hours of direct patient care per week | 32.6 (11.2) | 31.8 (11.0) | 32.4 (11.1) |
| Emergency department HCP | 375 (26%) | 202 (23%) | 328 (26%) |
| Site | |||
| Kaiser Permanente Northwest, Oregon | 418 (29%) | 286 (33%) | 395 (32%) |
| Scott & White Healthcare, Texas | 999 (71%) | 579 (67%) | 859 (69%) |
| Timing of sera collection | |||
| No. of days from preseason serum to 2010–2011 TIV | 15 (13) | ||
| No. of days from 2010–2011 TIV to post-TIV serum | 31 (8) | ||
| No. of days from preseason to end-of-season serum | 212 (15) | ||
| Influenza vaccination history | |||
| 2009–2010 seasonal influenza (TIV or LAIV) vaccination | 1007 (71%) | 736 (85%) | 894 (71%) |
| MIIV vaccination | 598 (42%) | 489 (57%) | 545 (43%) |
| 2010–2011 seasonal TIV vaccination | 936 (66%) | 865 (100%) | 894 (71%) |
| Vaccination interactions for 2009–2010 and 2010–2011 | |||
| No MIIV and No 2010–2011 TIV | 398 (28%) | 0 (0%) | 304 (24%) |
| No MIIV and Yes 2010–2011 TIV | 421 (30%) | 376 (43%) | 405 (32%) |
| Yes MIIV and No 2010–2011 TIV | 83 (6%) | 0 (0%) | 56 (4%) |
| Yes MIIV and Yes 2010–2011 TIV | 515 (36%) | 489 (57%) | 489 (39%) |
| Preseason serum HI antibody titer | |||
| GMT of A(H1N1)pdm09 HI titers | 11.9 (3.1) | 12.4 (3.1) | 11.9 (3.1) |
| Ordinala A(H1N1)pdm09 HI level | 1.3 (1.6) | 1.3 (1.6) | 1.2 (1.6) |
Data are presented as mean (SD) or No. (%).
Abbreviations: GMT, geometric mean titer; HCP, healthcare personnel; HI, hemagglutination inhibition antibody; LAIV, live attenuated influenza vaccine; MAARI, medically attended acute respiratory illness; MIIV, 2009–2010 A(H1N1) pandemic monovalent inactivated influenza vaccine; TIV, trivalent inactivated vaccine.
a Ordinal HI levels are represented with 0–9 levels based on log transformation of HI titers: Log2 (HI titer/5).