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Duration of protection after first dose of acellular pertussis vaccine in infants
Helen E Quinn1, Thomas L Snelling, Kristine K Macartney
1National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, and.
Insights
The diphtheria-tetanus-acellular pertussis (DTaP) vaccine provides strong protection against pertussis in infants. Vaccine effectiveness wanes by age 4 without a booster dose.
Area of Science:
- Immunology
- Vaccinology
- Pediatric Infectious Diseases
Background:
- Limited data exist on diphtheria-tetanus-acellular pertussis (DTaP) vaccine effectiveness (VE) in the first four years of life.
- Australia's DTaP vaccination schedule omits the fourth dose until age 4, differing from other countries.
Purpose of the Study:
- To evaluate the DTaP vaccine effectiveness (VE) in Australian children.
- To assess VE based on the number of doses received before 6 months and from 6 months of age.
Main Methods:
- A case-control study design was employed, matching pertussis cases to controls from an immunization register.
- Data were collected for children aged 2 to 47 months between January 2005 and December 2009.
- Vaccine effectiveness was calculated as (1 - odds ratio) × 100%.
Main Results:
- Two doses of DTaP before 6 months showed 83.0% VE against pertussis hospitalization.
- Three doses of DTaP from 6 months provided 83.5% VE against reported pertussis at 6-11 months.
- VE declined to 70.7% at 2-3 years and 59.2% at 3-4 years.
Conclusions:
- The DTaP vaccine offers significant protection against pertussis from the first dose in infancy.
- Without a booster, the protection from three DTaP doses diminishes more rapidly between ages 2 and 4 than previously observed in older children receiving five doses.
Objective:
Data on the effectiveness of the diphtheria-tetanus-acellular pertussis (DTaP) vaccine in the first 4 years of life are sparse. We evaluated the vaccine effectiveness (VE) of 1 and 2 doses of DTaP before 6 months of age and of 3 doses from 6 months of age in Australia, where, since 2003, a fourth dose is not given until 4 years.
Methods:
We matched reported pertussis cases aged 2 to 47 months between January 2005 and December 2009 to controls from a population-based immunization register by date of birth and region of residence. VE by number of doses and age group was calculated as (1 - odds ratio) × 100%.
Results:
VE against hospitalization increased from 55.3% (95% confidence interval [CI], 42.7%-65.1%) for 1 dose before 4 months of age to 83.0% (95% CI, 70.2%-90.3%) for 2 doses before 6 months. The VE of 3 doses of DTaP against all reported pertussis was 83.5% (95% CI, 79.1%-87.8%) between 6 and 11 months, declining to 70.7% (95% CI, 64.5%-75.8%) between 2 and 3 years of age and 59.2% (95% CI, 51.0%-66.0%) between 3 and 4 years of age.
Conclusions:
DTaP provided good protection against pertussis in the first year of life from the first dose. Without a booster dose, the effectiveness of 3 doses waned more rapidly from 2 to 4 years of age than previously documented for children >6 years of age who had received 5 doses.
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