08/16/2012

Christina Elston

A new study has revealed that the switch to a pertussis vaccine with fewer side effects more than a decade ago may have left children slightly more vulnerable to the illness.

Keep an eye out for whooping cough (a.k.a. pertussis) as your kids start the new school year. A new study has revealed that the switch to a pertussis vaccine with fewer side effects more than a decade ago may have left children slightly more vulnerable to the illness – a highly contagious respiratory infection where thick mucus in the windpipe can make it difficult to eat, drink and breathe.

Australian researchers looked at data on 40,000 Queensland children born in 1998 who had been vaccinated against whooping cough. Those receiving the newer vaccine – made with just a few pieces of killed pertussis bacteria – were three times more likely to develop whooping cough than those treated with the older vaccine made from whole, killed pertussis cells.

In the mid-1990s, the vaccine, then known as DTwP (diphtheria-tetanus–whole-cell pertussis), was changed to the DTaP (diphtheria-tetanus-acellular pertussis) vaccine currently available. The newer vaccine was found to cause far fewer side effects – including pain and swelling at the injection site, fever and prolonged crying – than the DTwP vaccine.
While the study found the newer vaccine to be less effective, researchers are stressing the following:

• Vaccination still offers the best protection against whooping cough.

• The increased risk of developing whooping cough is small, leading to just one extra case per year for every 500 vaccinated children.

• Doctors need to consider whooping cough as a diagnosis, even in children who’ve been vaccinated.

Whooping cough cases in the United States are on track to reach record highs this year, according to the national Centers for Disease Control (CDC). There have been approximately 18,000 cases reported as of this summer, more than twice the number reported up to this time last year.

CDC attributes the upward trend primarily to the fact that potency of the DTaP vaccine begins to fade after about 10 years, and the agency is urging booster shots for teens and adults. While whooping cough isn’t generally fatal in teens and adults, it can be deadly in infants. The CDC reports that nine babies in the U.S. have already died from the disease this year.

The vaccine study was published in a recent issue of the Journal of the American Medical Association (JAMA).