Effectiveness of Population-Based Immunization Recall In a Large Urban Area

Background:  The effectiveness of using a statewide immunization registry to conduct population-based immunization recall for a public health jurisdiction has not been documented.

Objectives:  To assess the effectiveness of population-based immunization recall in a large urban area with historically low vaccination rates using a centralized approach with a statewide immunization information system (IIS).

Methods:  Eligible children were identified in the Michigan Care Improvement Registry (MCIR) as being not up-to-date at 19 months and residing in Wayne County, Michigan (n=4,013). Children were randomized (recall, no recall) in each of four cycles (June 2008, September 2008, January 2009, June 2009). Recall notices were sent by US mail; 625 children with undeliverable addresses (16%) were excluded from analysis. The main outcome, assessed at 60 days following recall, was MCIR evidence of immunization activity (any vs. none). Children with any immunization activity were categorized as: 1+ new dose administered following recall; 1+ historical dose (i.e., administered prior to recall but subsequently recorded in MCIR); any waiver of 1+ dose.

Results:  The study population included 2,507 children in the recall group and 881 in the no-recall group.  Overall, 28% of the recall group and 20% of the no-recall group had MCIR evidence of some form of immunization activity (p<0.0001). The most common categories of immunization activity were 1+ dose administered (20% recall group vs. 16% no-recall group, p=0.007); and 1+ historical dose (9% recall group vs. 4% no-recall group, p<0.0001.) Waivers were uncommon in both  recall (0.1%) and no-recall (0.2%) groups.  In the 60 days following recall, children in the recall group were more likely than children not recalled to become up-to-date (19% vs. 12%, p<0.0001).  

Conclusions:  Population-based immunization recall prompted both newly-administered doses as well as the entry of missing doses into a statewide IIS.  Recall using an IIS appears to be effective mechanism to improve vaccination rates.