HealthDay News — After receiving the last of five required doses of pertussis vaccine, a child’s protection from the disease rapidly declines, study results reveal.
“Our findings highlight the need to develop new pertussis-containing vaccines that will provide long-lasting immunity,” Nicola P. Klein, MD, PhD, from the Kaiser Permanente Vaccine Study Center in Oakland, Calif., and colleagues reported in the New England Journal of Medicine.
They compared the risk for pertussis based on time elapsed since administration of the last of five required doses of the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine, which is routinely given to children aged 4 to 6 years prior to starting kindergarten.
The study involved 277 children aged 4 to 12 years who tested positive for pertussis on polymerase chain reaction assay, 3,318 children negative for pertussis and 6,086 matched controls. Infection rates were examined from 2006 to 2011, and included a large pertussis outbreak in 2010.
Pertussis-positive children were significantly more likely to have received their last DTaP dose earlier than both other groups, the researchers found. Compared with the pertussis-negative group, pertussis-positive children had an odds ratio of 1.42 per year for acquiring pertussis after the fifth dose.
Based on these findings, if the initial effectiveness of the fifth DTaP dose is 95%, it would decrease to 71% after five years. Consequently if the effectiveness was 90% after the last DTaP dose, it would decrease to 42% after five years, the researchers explained.
“In conclusion, our evaluation of data from a large pertussis outbreak in California showed that protection from disease after a fifth dose of DTaP among children who had received only DTaP vaccines was relatively short-lived and waned substantially each year,” the researchers wrote.
The researchers emphasized the importance of DTaP vaccines in protecting against whooping cough, despite the study findings, adding that “following current CDC recommendations remain important.”
Recommendations currently state that health care providers should administer the first three shots at ages 2, 4, and 6 months. Shot four should be given at age 15 through 18 months, and the last shot, when a child enters school at 4 through 6 years of age.