TUESDAY, July 31 (HealthDay News) -- A change in vaccine composition may partly explain current whooping cough outbreaks in the United States and Australia, researchers say.
In the 1990s, a switch was made from diphtheria-tetanus-whole cell pertussis (DTwP) vaccine to diphtheria-tetanus-acellular pertussis (DTaP) vaccine to reduce side effects. It's possible that the newer vaccine is less effective and wears off faster, Australian researchers suggest.
"Our findings don't change the fact that vaccinations remain the best way to prevent whooping cough," said lead researcher Stephen Lambert, an associate professor at the Queensland Children's Medical Research Institute of the University of Queensland in Brisbane.
"Children who develop pertussis [whooping cough] despite being vaccinated have milder symptoms, reduced duration of illness and are less infectious to others than children who have not received their vaccines," he added.
Moreover, doctors shouldn't exclude whooping cough as a diagnosis just because a child has had all of the recommended vaccines, Lambert said.
Whooping cough -- so-called because of the distinctive crowing sound or "whoop" it causes -- is highly contagious. More than twice as many cases have been reported in the United States so far this year compared to last year, and already nine babies have died, according to the U.S. Centers for Disease Control and Prevention. "We may be on track for a record-high pertussis rate this year," Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, said recently.
For the study, published in the Aug. 1 issue of the Journal of the American Medical Association, Lambert's team collected data on more than 58,000 Australian children born in 1998. More than 40,000 of them received three doses of a pertussis vaccine.
Children who received the DTaP vacc
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