Medicare Influenza Immunization Rates, West Virginia, 1993–2004
| Year | Claims* % | BRFSS† % | Lagged Prediction‡ % | Estimated Nonbilling§ % |
|---|---|---|---|---|
| Note: BRFSS = Behavioral Risk Factor Surveillance System. | ||||
| * Claims represent proportion of Medicare beneficiaries =65 years who had claims for influenza vaccine between September 1 of the indicated year and January 31 of the subsequent year. | ||||
| † BRFSS is the proportion of the West Virginia population =65 years who indicated having an influenza immunization in the previous 12 months during the indicated year. | ||||
| ‡ Lagged prediction is the predicted true proportion of the West Virginia population =65 years who received influenza immunization, based on the following year’s BRFSS results, with a sensitivity of 0.98 and specificity of 0.71, after MacDonald et al.27 | ||||
| § Estimated nonbilling is the difference between the lagged prediction and the claims rates of influenza immunization. | ||||
| 1993 | – | 49.8 | – | – |
| 1994 | 35.7 | – | 35.1 | −0.6 |
| 1995 | 37.1 | 53.2 | – | – |
| 1996 | 37.0 | – | 42.3 | 5.3 |
| 1997 | 39.1 | 58.2 | 49.1 | 10.0 |
| 1998 | 39.4 | 62.9 | 49.1 | 9.7 |
| 1999 | 42.5 | 62.9 | – | – |
| 2000 | 36.5 | – | 47.4 | 10.9 |
| 2001 | 38.9 | 61.7 | 53.3 | 14.4 |
| 2002 | 41.8 | 65.8 | 58.1 | 16.3 |
| 2003 | 41.2 | 69.1 | 56.4 | 15.2 |
| 2004 | 27.1 | 67.9 | 50.1 | 23.1 |
| 2005 | – | 63.6 | – | – |