Seasonal influenza vaccination reminders for children with high-risk conditions: a registry-based randomized trial

BACKGROUND: Children with chronic conditions have an increased risk of complications from influenza and have low influenza vaccination rates. PURPOSE: To assess the feasibility and effectiveness of using a statewide immunization information system (IIS) for seasonal influenza vaccine reminders from local health departments (LHDs) targeting children with high-risk conditions. DESIGN: A randomized community intervention. SETTING/PARTICIPANTS: The study was conducted in a population of 3618 children aged 24-60 months with a high-risk condition residing in three Michigan counties. Children were identified using a statewide IIS in October 2008. INTERVENTION: Children were randomized to intervention (reminder) or control (no reminder) groups. Reminders for seasonal influenza vaccination were mailed by LHDs in November 2008. MAIN OUTCOME MEASURES: Feasibility of notification (address validity- address deliverability) was assessed (November 2008-February 2009)- and frequencies of notification feasibility measures were determined (analyses conducted in 2010). Effectiveness of notification (seasonal influenza vaccine receipt) was assessed using bivariate logistic regression. RESULTS: Among 3618 children with a high-risk condition- 2730 (75.5%) had not received a 2008-2009 influenza vaccination and were eligible at the time of notification. Among children assigned to the reminder group (n=1374)- 42.6% had an address determined to be either invalid- undeliverable- or both. Among those with valid addresses (n=2001)- a greater percentage of children with deliverable reminders received at least one influenza vaccination (30.8%) during the outcome observation period than did children assigned to no reminder (24.3%- OR=1.39- 95% CI=1.13- 1.72)/ children with an undeliverable reminder had an influenza vaccination rate (22.8%) similar to children assigned to no reminder. CONCLUSIONS: Receipt of a reminder was positively associated with seasonal influenza vaccination. However- more than 40% of children assigned to receive a reminder were determined to have an invalid or undeliverable address- emphasizing the need for increased quality of IIS contact information. TRIAL REGISTRATION: This study is registered at www.ClinicalTrials.gov NCT01431183.