A study published today in The New England Journal of Medicine evaluated the duration of protection against whooping cough after children get the DTaP shot.  Researchers wanted to find out how long the shot lasts. DTaP shots are given to infants, toddlers, and kindergarteners (schedule below) to protect them from three infections (Diptheria, Tetanus, and Pertussis –whooping cough). After these childhood vaccines, we give a “booster” shot at age 11. Because we know that many babies who get whooping cough are infected by teens and adults, all teens and adults are now recommended to get a Tdap shot to protect themselves and those vulnerable against whooping cough.

As researchers seek to understand the recent epidemics of whooping cough in the US, they have found more and more that the causes of these epidemics are multifactorial. Not only is it unvaccinated populations that allow epidemics, it may be waning immunity from shots given previously and waning immunity to natural infection, as well. Previously, it’s been estimated that our immunity to whooping cough wanes anywhere between 4 and 20 years after we get whooping cough, and that it may wane 4 to 12 years after the shot.

A little history: back in the 1990’s we switched from using the “whole cell pertussis” shot to using a vaccine that is “acellular.” Some health officials have had concerns that this “acellular vaccine” may not protect children as long. Although it does a great job protecting infants and toddlers, it may not last as long as previous immunizations. Some have wondered how long the kindergarten shot protects our children…

Physicians at Kaiser Permanente reviewed information about children in California during the 2010 whooping cough outbreak. What they found may have significant effects on how to protect our children going forward:

Timing Matters: Waning Protection After 5Th Dose:

  • Design: Researches compared 277 children with lab-tested whooping cough between 2006 and 2011. They compared the children with whooping cough to nearly 10,000 controls (children who tested negative for pertussis & children who were matched controls).
  • Results: Children who were diagnosed with whooping cough were more likely to have had the Kindergarten dose earlier. More of those who ended up getting whooping cough may have had the shot when they were just 4 years of age. The next booster isn’t until age 11 years so in the 7 years between the shots, their immunity may have waned.
  • Conclusions: After the 5th dose of whooping cough shot (DTaP), the odds of acquiring pertussis increased by an average of 42% per year. This means, for every year that passes after a child gets the Kindergarten shot, the likelihood that they could get whooping cough may increase until the next booster.

What To Do To Help Protect Your Family From Whooping Cough

  • We still know the best way to protect against whooping cough is to get everyone in your family immunized. If we immunize our babies, toddlers and infants per the schedule, and get the updates as adolescents and adults, we reduce the likelihood for infection in all. We also know that as time unfolds we may need additional boosters.
  • Booster shots “boost” your child’s and your family’s immunity. Stay up to date. Here’s a post from Dr Ed Marcuse on pertussis boosters. The data from this NEJM study may help the CDC and the American Academy of Pediatrics better know when to recommend that our children get the next booster.
  • Keep learning. It’s a part of being human to lose immunity to infections, both from natural infection and from vaccines. Over time, our bodies forget how to protect against infections. This study points out that the new generation of children who have had only “acellular” pertussis vaccines may need additional boosters to keep them safe. Time will tell. New recommendations may come out later this year or next.

Does this make sense? Tell me what I can explain…