Learning Objectives for this Presentation:
By the end of the presentation participants will be able to describe patterns in the use of Td and Tdap in Michigan.

Background:
Tdap resembles Td, but boosts immunity to pertussis in addition to tetanus and diphtheria. Tdap was FDA-approved in mid-2005 and ACIP-recommended in March 2006. Although few adolescents received it before the 2005-2006 school year, substantial uptake was expected before the 2006-2007 school year. A Td booster is required for Michigan students if 10+ years have passed since the last tetanus or diphtheria vaccination.

Objectives:
Determine to what extent Tdap is replacing Td in Michigan.

Methods:
The Michigan Care Improvement Registry (MCIR) provided records of Td-containing vaccinations since 1997 on 12 Oct. 2006; they were charted by year of vaccination, vaccine type, and age at vaccination.

Results:
Td administration peaked every August since 1997 (except during the 2001 Td shortage). In 2006, the percentage of Td-containing vaccines that were Tdap increased steadily from 34% in January, leveling off at ~78% in August and later months. For the 12-month period ending in mid-Oct., 134,929 Td-containing vaccines were recorded (similar to Michigan's birth cohort of ~130,000). Of these, 4.5% were in children < 11y, 36% in children 11-12y, and 59.5% in persons > 12y (similar to the previous 4 years). 69.5% of Td-containing vaccinations in children aged 11-12y were Tdap, compared to 54.5% for persons > 12y. However, coverage with Td & Tdap remained low (e.g., 19% of persons aged 11-12y on 12 Oct. 2006 had 1+ Td-containing vaccines recorded).

Conclusions:
More Tdap than Td was reported in Michigan in 2006. This is a promising sign for pertussis control efforts. Reporting to MCIR of Td-containing vaccines should be improved.