Table 3.
Unadjusted and Adjusted Estimates of Influenza Vaccine Effectiveness, Overall and Stratified by Age and Virus Type, Subtype, or Lineage—United States, 2016–2017 Influenza Season
| Influenza (Sub)Type/Age Group | Influenza Positive | Influenza Negative | Unadjusted | Adjusteda | ||||
|---|---|---|---|---|---|---|---|---|
| No. Vaccinated/Total | % | No. Vaccinated/Total | % | VE % | (95% CI) | VE % | (95% CI) | |
| Influenza A and B | ||||||||
| All ages ≥6 months | 866/2043 | 42 | 2629/5040 | 52 | 33 | (25 to 39) | 40 | (32 to 46) |
| 6 months–8 years | 93/338 | 28 | 581/1181 | 49 | 61 | (49 to 70) | 57 | (43 to 68) |
| 9–17 years | 121/403 | 30 | 243/608 | 40 | 36 | (16 to 51) | 36 | (15 to 52) |
| 18–49 years | 198/528 | 38 | 711/1637 | 43 | 22 | (4 to 36) | 19 | (0 to 34) |
| 50–64 years | 206/447 | 46 | 533/915 | 58 | 39 | (23 to 51) | 40 | (24 to 53) |
| ≥65 years | 248/327 | 76 | 561/699 | 80 | 23 | (−5 to 44) | 20 | (−11 to 43) |
| Influenza A(H3N2) | ||||||||
| All ages ≥6 months | 604/1342 | 45 | 2629/5040 | 52 | 25 | (15 to 33) | 33 | (23 to 41) |
| 6 months–8 years | 60/190 | 32 | 581/1181 | 49 | 52 | (34 to 66) | 49 | (28 to 64) |
| 9–17 years | 76/259 | 29 | 243/608 | 40 | 38 | (15 to 54) | 33 | (7 to 52) |
| 18–49 years | 138/351 | 39 | 711/1637 | 43 | 16 | (−7 to 33) | 13 | (−11 to 32) |
| 50–64 years | 148/304 | 49 | 533/915 | 58 | 32 | (12 to 48) | 31 | (9 to 47) |
| ≥65 years | 182/238 | 77 | 561/699 | 80 | 20 | (−14 to 44) | 21 | (−15 to 45) |
| Influenza B | ||||||||
| All ages ≥6 months | 236/648 | 36 | 2629/5040 | 52 | 47 | (38 to 56) | 53 | (43 to 61) |
| Influenza B/Yamagata | ||||||||
| All ages ≥6 months | 213/577 | 37 | 2629/5040 | 52 | 46 | (36 to 55) | 52 | (42 to 61) |
| 6 months–8 years | 22/113 | 20 | 581/1181 | 49 | 75 | (60 to 85) | 73 | (54 to 84) |
| 9–17 years | 39/122 | 32 | 243/608 | 40 | 29 | (−7 to 53) | 37 | (1 to 60) |
| 18–49 years | 46/137 | 34 | 711/1637 | 43 | 34 | (5 to 54) | 30 | (−3 to 53) |
| 50–64 years | 53/129 | 41 | 533/915 | 58 | 50 | (27 to 66) | 63 | (42 to 76) |
| ≥65 years | 53/76 | 70 | 561/699 | 80 | 43 | (4 to 66) | 34 | (−24 to 65) |
| Influenza B/Victoria | ||||||||
| All ages ≥6 months | 21/63 | 33 | 2629/5040 | 52 | 54 | (22 to 73) | 56 | (23 to 75) |
Vaccine effectiveness was estimated by comparing the odds of vaccination influenza case patients and non-case patients and calculated as 100 × (1 – odds ratio) in logistic regression models. Vaccination includes any 2016–2017 inactivated influenza vaccine.
Abbreviations: CI, confidence interval; REF, referent group (1.0); VE, vaccine effectiveness
aModels were adjusted for study site, patient age in months, presence of any high-risk health condition and calendar time (two week intervals).