Impact of the 2004 influenza vaccine shortage on repeat immunization rates.

Abstract

We assessed the impact of the severe influenza vaccine shortage of 2004 on individual physicians' immunization performance. Using 1998-2004 Medicare claims data, we monitored the physician continuity rate (proportion of patients receiving influenza immunization from a physician in 1 year who received a subsequent immunization from the same physician the subsequent year) and other clinician rate (proportion of patients with claims from 1 physician in 1 year with a claim from another clinician the subsequent year) in West Virginia Medicare beneficiaries from 2000-2004. We examined vaccine claim trends by clinician and surveys of self-reported immunization to determine whether patients received vaccine from nonphysician clinicians or went without immunization each year. Claims-based influenza vaccination rates increased from 35.5% to 41.3% from 2000-2003, reflecting historical trends, before declining 14.1% in 2004. Median continuity rates among the 723 to 849 physicians claiming 25 or more influenza immunizations from 2000-2003 increased from 47% in 2000-2001 to 54% in 2002-2003; then fell to 3% in 2003-2004. The number of physicians filing 100 or more claims declined from 337 in 2003 to 130 in 2004. More than 25% of physicians had no repeat vaccinations of the same beneficiaries in 2004. Trends in clinician type and survey data indicated a shift of many beneficiaries to mass vaccinators and institutional providers; however, compared with previous years, there was an estimated 8% increase in 2004 in the number of West Virginia beneficiaries who did not receive vaccine. The 2004 vaccine shortage had a severe impact on influenza immunization rates in private physician's offices, disrupting continuity of care.