I’m not surprised to hear that the CDC studies found pertussis immunity waned after the fifth childhood acellular vaccine dose in some 7- to 10-year-olds. The half-life of antibody-mediated immunity against pertussis toxin is fairly short-lived, about 36 days. By the time children receive the fifth dose they also produce cellular immunity, but this response is not as robust as after other vaccines, such as the measles vaccine.
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Most children now receive their fifth pertussis dose at age 4 years because that’s when they start school, and many states have laws that mandate the fifth dose at that time. That starts the child’s vaccination clock early, but it would be hard to switch to routinely giving the fifth dose at an older age. And we will never go back to the cellular vaccine. It’s time to start thinking about trying to produce a better pertussis vaccine, but vaccines are developed by companies and they need to believe they will recoup their development costs.
Children born in 1998 were the first cohort to exclusively receive the acellular vaccine. Following that, the first big U.S. pertussis outbreak occurred in 2005. Pertussis outbreaks occur in 5-year cycles, so the next big outbreak was in 2010. The California epidemic was caused by underimmunization of some children, and by waning immunity in fully vaccinated children. It showed that we are not where we need to be to have herd immunity. The 2010 California outbreak caught everyone’s attention. It demonstrated that we need a better vaccine, and perhaps we also need to change the vaccination schedule.
Dr. Carol J. Baker is professor of pediatrics and microbiology at Baylor College of Medicine in Houston. Dr. Baker said that she had no relevant financial disclosures. She made these remarks in an interview.
FROM THE ANNUAL MEETING OF THE INFECTIOUS DISEASES SOCIETY OF AMERICA
