NMA: Nonprescription Medicines Academy

Study Finds Waning Protection from DTaP Vaccine

October 17th, 2012

A study that assessed the risk of pertussis (whooping cough) in children 4 to 12 years of age in California found that protection from disease waned during the 5 years after a fifth dose of diphtheria–tetanus–acellular pertussis (DTaP) vaccine, such that the odds of acquiring pertussis increased by an average of 42% each year from 2006 to 2011. The evaluation period included a large outbreak of pertussis in 2010.

The case-control study from the Kaiser Permanente Vaccine Study Center is the first to focus specifically on the large population of highly vaccinated children who received DTaP vaccines exclusively since birth. Researchers compared 277 children (4 to 12 years of age) who were positive for pertussis with 3,318 children who were negative for pertussis and 6,086 matched controls. Comparison with negative controls yielded an odds ratio of 1.42 (95% CI, 1.21–1.66).

According to the authors, the amount of protection remaining after 5 years appears to depend heavily on the initial effectiveness of the fifth dose of DTaP. If the initial effectiveness was 95%, the effectiveness of DTaP would decrease to 71% after 5 years. If the initial effectiveness was 90%, the effectiveness would decrease to 42% after 5 years.

N Engl J Med. 2012; 367:1012-9.