Pertussis Vaccine Loses Power Over Time

A new study suggests that protection from the childhood series of the diphtheria, tetanus and acellular pertussis (DTaP) vaccine fades within five years of the final dose. The study, published in the New England Journal of Medicine, involved data from 2006 to 2011 on children in Northern California who received a fifth dose of DTaP between the recommended ages of 4 and 6. Of those children, 277 had a positive PCR test for pertussis, 3,318 had a negative PCR test and 6,086 matched controls who were not tested for the disease. The researchers found that a larger period of time from the fifth dose of the vaccine was linked to a higher percentage of positive PCR tests, with 0.8 percent of the tests coming up positive when they were conducted 15 days to one year after the last dose and 18.5 percent testing positive six to eight years after the fifth dose. “This is an important paper, as it adds to our understanding of the waning immunity with DTaP vaccine,” said Dr. Mark Sawyer, chair of the pertussis vaccines working group for the Advisory Committee on Immunization Practices. “Although the current vaccines are less than perfect, they are all we have to protect the population from pertussis.”