OAKLAND, Calif. − Protection against whooping cough (also called pertussis) waned during the five years after the fifth dose of the combined diphtheria, tetanus, acellular pertussis (DTaP) vaccine, according to researchers from the Kaiser Permanente Vaccine Study Center. The fifth dose of DTaP is routinely given to 4- to 6-year-old children prior to starting kindergarten.
The study appears in the current online issue of the New England Journal of Medicine.
This is the first study to specifically focus on the large population of highly vaccinated children who had exclusively received DTaP vaccines since birth and for whom enough time had passed since their fifth dose that DTaP vaccine waning could be measured, said the researchers. They explained that the study period included a large pertussis outbreak that occurred in California during 2010. Researchers examined the relationship between time since vaccination with the likelihood of a positive pertussis test in the Kaiser Permanente Northern California population, which includes 3.3 million members in an integrated care system with electronic medical records and a central laboratory.
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 separately with 6,086 matched controls. They assessed the risk of pertussis in children from 2006 to 2011 in California relative to the time since the fifth dose of DTaP and found that protection from pertussis after the fifth dose of DTaP vaccine wanes more than 40 percent each year. The amount of protection remaining after five years depends heavily on the initial effectiveness of the fifth dose of DTaP, according to Nicola Klein, MD, PhD, co-director of the Kaiser Permanente Vaccine Study Center and the lead author of the study.
If the initial effectiveness of the fifth dose of DTaP was 95 percent, the effectiveness of DTaP would decrease to 71 percent after five years. Whereas if the initial effectiveness was 90 percent, it would decline to 42 percent after five years, explained the researchers.
"The findings suggest that whooping cough control measures may need to be reconsidered. Prevention of future outbreaks may be best achieved by developing new pertussis-containing vaccines or reformulating current vaccines to provide long-lasting immunity," said Klein.
"That said, the DTaP vaccine is effective and remains an important tool for protection against whooping cough for children and the communities in which they live, and following current CDC recommendations remains important."
The CDC currently recommends five DTaP shots for children. The first three shots are given at 2, 4, and 6 months of age. The fourth shot is given at 15 through 18 months of age, and a fifth shot is given when a child enters school, at 4 through 6 years of age.
The first pertussis vaccine was developed in the 1930s and was in widespread use by the mid-1940s, when pertussis vaccine was combined with diphtheria and tetanus toxoids to make the combination whole cell pertussis vaccine DTP. In 1991, concerns about DTP safety led to the development of the acellular pertussis DTaP vaccines that are associated with fewer side effects. DTaP vaccines have completely replaced the whole cell DTP vaccines in the United States as well as in many countries around the world.
Additional investigators on the paper include: Joan Bartlett, MPH, MPP; Bruce Fireman, MA, with the Kaiser Permanente Northern California Division of Research ; Ali Rowhani-Rahbar, MD, MPH, PhD; and Roger Baxter, MD, co-director of the Kaiser Permanente Vaccine Study Center.
The research was funded by Kaiser Permanente.
About the Kaiser Permanente Vaccine Study Center
Founded in 1985, the Kaiser Permanente Vaccine Study Center began as a way of responding to numerous requests to use Kaiser Permanente's large population for vaccine efficacy studies. Key studies have focused on Haemophilus influenza, type B (Hib), chickenpox, pneumococcus, rotavirus, and flu vaccines. The center operates 31 sites in Northern California and collaborates with Kaiser Permanente's Northwest, Hawaii, and Colorado regions as well as participates in several Centers for Disease Control and Prevention and National Institutes of Health studies. For more information, visit www.dor.kaiser.org/external/research/topics/Vaccine_Epidemiology/.
About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR's 500-plus staff is working on more than 250 epidemiological and health services research projects. For more information, visit www.dor.kaiser.org/.
About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 9 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/newscenter.