Waning Whooping Cough Immunity Blamed in Outbreaks
Teens have very little protection just a few years after vaccination, study finds
By Amy Norton
FRIDAY, Feb. 5, 2016 (HealthDay News) -- The booster shot given to pre-teens to ward off whooping cough only works for a short time -- a fact that has played a big role in recent outbreaks in California, a new study finds.
The study, of children in one large California health plan, found that the whooping cough booster shot offered "moderate" protection for about a year. But that immunity waned so quickly that little protection remained after two or three years.
Experts said the findings, reported online Feb. 5 and in the March print issue of Pediatrics, underscore the limits of today's whooping cough vaccines.
It's been clear for years that cases of whooping cough, or pertussis, are rising in the United States. In 2012, more than 48,000 cases were reported nationwide -- the highest number since 1955, according to the U.S. Centers for Disease Control and Prevention.
What's more, the agency says, older children and teenagers are accounting for a growing proportion of cases.
A major reason, experts believe, is that in the 1990s, U.S. health officials switched from the traditional whooping cough vaccine to a new one known as DTaP -- which also protects against diphtheria and tetanus. DTaP works well in the short term, the CDC says, but slowly wanes each year after a child's final dose, which is given around age 5.
So a booster shot, called Tdap, is routinely given to kids at age 11 or 12. But that shot doesn't last long either.
"The issue is, the old vaccine against whooping cough had a difficult safety profile," explained Dr. Paul Offit, director of the Vaccine Education Center and a professor of infectious diseases at Children's Hospital of Philadelphia.
It could cause high fevers and seizures in young children, he said -- which understandably worried parents. There were also concerns about possible, albeit rare, neurological effects, Offit added.
That led to the development of DTaP, which has far fewer antigens than the old vaccine, Offit said. Antigens are proteins that trigger an immune system response; with fewer antigens, DTaP is much less likely to cause side effects. But it also offers shorter-lived immunity.