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Factors influencing tetanus toxoid-containing vaccination (TTCV) coverage

- including Tdap - among U.S. adults

National Immunization ConferenceApril 21, 2010 - Atlanta, GA

Brady Miller, MPH

Health Services Research and Evaluation BranchImmunization Services Division

Background

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Background -- Tetanus

• Tetanus is well controlled in the U.S.

– Only 28 reported cases in 2007

– Older adults remain at risk due to low vaccination rates• Persons aged ≥65 years contributed 10

(36%) reported cases in 2007

3CDC. MMWR 2009;56:1-98.

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ACIP recommendation

• In 2005, the Advisory Committee for Immunization Practices (ACIP) recommended tetanus, diphtheria, acellular pertussis (Tdap) vaccine for all persons aged 10-64 years

– Priority groups• Health care personnel (HCP)• Adults with infant contact (<1 year of age)

5Kretsinger et al. MMWR Recomm Rep 2006;55(RR-17):1-38.

Study Objectives

1. Estimate changes in tetanus toxoid-containing vaccination (TTCV) coverage among adults aged ≥18 years from 1999 and 2008

2. Estimate Tdap coverage among adults aged 18-64 years since the ACIP recommendation

3. Identify potential barriers to Tdap vaccination among adults aged 18-64 years

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Methods

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Methods: National Surveys

• National Health Interview Survey (NHIS)

– 1999, 2008

– Vaccination coverage estimates

• National Immunization Survey (NIS)

– NIS-Adult 2007

– Potential barriers to vaccination

– Interviews conducted approximately 6 months after ACIP recommendation published

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Results

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Self-reported TTCV coverage (previous 10 years) among U.S. adults – NHIS, 1999, 2008

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- Survey question was, “Have you received a tetanus shot in the past 10 years?”- Of 9 characteristics analyzed (age, sex, race, poverty level, education, medical insurance, visited health care provider, received influenza vaccine, or visited emergency department (past 12 mo.)), only age was significantly different between 1999 and 2008

Self-reported Tdap vaccination coverage among U.S. adults – NHIS, 2008

11Statistically significant (α=0.05, two-tailed)

Existing knowledge of Tdap among unvaccinated U.S. adults – NIS, 2007

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Sample

Heard of Tdap* (%) p-value

Total 3,682 19.3

Employment in health care setting

<0.01

Yes 447 40.2

No 3,143 16.6

Infant contact 0.11

Yes 666 23.8

No 2,923 18.3

* Survey question was, “Had you ever heard of the tetanus, diphtheria, acellular pertussis vaccine?”

Prevalence of doctor recommendation for Tdap among unvaccinated U.S. adults* –

NIS, 2007

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Sample

Received recommendation†

(%) p-value

Total 677 13.3

Employment in health care setting

0.15

Yes 172 19.0

No 504 10.0

Infant contact 0.94

Yes 145 12.7

No 532 13.1* Only respondents who had reported existing knowledge of Tdap were asked about doctor recommendation.† Survey question was, “Has a doctor recommended that you get Tdap [past two years]?”

Relationship of doctor recommendation with intent to receive Tdap vaccine, among unvaccinated U.S. adults* – NIS, 2007

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Sample

Would receive vaccine if recommended*

(%) p-value

Total 3,592 81.2

Employment in health care setting

0.21

Yes 408 79.5

No 3,005 81.6

Infant contact 0.01

Yes 637 86.9

No 2,775 79.9* Survey question was, “Would you get Tdap instead of Td if your doctor recommended it?”

Main reason* for not receiving Tdap, among unvaccinated U.S. adults† – NIS, 2007

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*Respondents were only allowed to give one reason† These persons stated that they either would not get the vaccination even if a doctor recommended it, or they did not receive Tdap despite receiving a TTCV since 2005** Responses included: cost, did not think about it, did not know should get one, did not want one, vaccine not effective, limited access, vaccine shortage, and other infrequent responses.

Limitations

1. Vaccination self-reported, so susceptible to recall bias

2. NIS-Adult 2007 was adjusted to account for persons without landline telephones, although some selection bias may remain

3. A number of responses from which information was incomplete (e.g., “don’t know”) was excluded from Tdap coverage estimate

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Conclusions

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Conclusions

• Objective #1: Estimate changes in TTCV coverage among adults aged ≥18 years from 1999 and 2008

• Conclusion #1: Overall, self-reported coverage has changed very little, despite increased vaccination rates among older adults in 2008

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Conclusions

• Objective #2: Estimate Tdap coverage among adults aged 18-64 years since the 2005 ACIP recommendation

• Conclusion #2: Three years after the recommendation, self-reported coverage remains low (5.9%) overall. HCP were more likely to be vaccinated than non-HCP, while vaccination among persons with and without infant contact was similar

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Conclusions

• Objective #3: Identify potential barriers to Tdap vaccination among adults aged 18-64 years

• Conclusion(s) #3:– Low awareness of vaccine existence, relative

absence of provider recommendations, and a low perceived risk among unvaccinated adults likely have contributed to low coverage thus far

– Despite this, many adults would be receptive to the idea of being vaccinated with Tdap

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Increasing vaccination coverage

• Raise awareness of Tdap vaccine

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• Encourage providers to recommend Tdap to patients

• Identification of persons with infant contact should be priority

• Risk of transmitting pertussis to infants should be communicated

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Acknowledgements

CDC

• Faruque Ahmed, PhD

• Gary Euler, DrPH

• Katrina Kretsinger, MD, MA

• Peng-Jun Lu, MD, PhD

The findings and conclusions in this presentation are those of the authors and do not necessarily represent

the official position of the CDC