Table 1.
Baseline Characteristics of the 1861 Participants, by Vaccination Group
| Characteristics | All Participants | |||||||
|---|---|---|---|---|---|---|---|---|
| Standard-dose quadrivalent vaccine, n = 508 | MF59-adjuvanted trivalent vaccine, n = 508 | High-dose trivalent vaccine, n = 510 | Recombinant-HA quadrivalent vaccine, n = 335 | |||||
| n | (%) | n | (%) | n | (%) | n | (%) | |
| Age, years | ||||||||
| 65–70 | 269 | (53%) | 248 | (49%) | 258 | (51%) | 171 | (51%) |
| 71–76 | 130 | (26%) | 149 | (29%) | 143 | (28%) | 82 | (24%) |
| 77–82 | 109 | (21%) | 111 | (22%) | 109 | (21%) | 82 | (24%) |
| Female sex | 301 | (59%) | 308 | (61%) | 327 | (64%) | 195 | (58%) |
| Underlying medical conditions | ||||||||
| Hypertension | 230 | (45%) | 262 | (52%) | 239 | (47%) | 161 | (48%) |
| Osteoarthritis | 110 | (22%) | 102 | (20%) | 109 | (21%) | 70 | (21%) |
| Diabetes | 98 | (19%) | 104 | (20%) | 88 | (17%) | 61 | (18%) |
| Heart diseases | 52 | (10%) | 47 | (9%) | 52 | (10%) | 29 | (9%) |
| Cancer | 46 | (9%) | 43 | (8%) | 40 | (8%) | 22 | (7%) |
| Othersa | 209 | (41%) | 221 | (44%) | 226 | (44%) | 141 | (42%) |
| Received influenza vaccination in 2016–2017 season | 328 | (65%) | 332 | (65%) | 351 | (69%) | 226 | (67%) |
| Number of times received influenza vaccination in the preceding 5 yearsb | ||||||||
| 0 | 126 | (25%) | 104 | (20%) | 111 | (22%) | 71 | (21%) |
| 1–2 | 113 | (22%) | 120 | (24%) | 112 | (22%) | 68 | (20%) |
| 3–4 | 54 | (11%) | 45 | (9%) | 61 | (12%) | 38 | (11%) |
| 5–6 | 195 | (38%) | 201 | (40%) | 212 | (42%) | 144 | (43%) |
Abbreviation: HA, hemagglutinin.
a
Other underlying conditions included: stroke, chronic lung disease, kidney disease, liver disease, depression or anxiety disorder, neurologic disorder, autoimmune disease, disease of the digestive system, hypothyroidism, dermatological disease, etc.
b
There were 6 possible influenza vaccines, including the 5 Northern hemisphere influenza vaccines from 2012–2013 through 2016–2017 plus the Southern hemisphere 2015 vaccine, which was available in Hong Kong for a special vaccination campaign [20]. The Southern hemisphere formulation is not usually available in Hong Kong.