Whooping cough efficacy declines after three years, study shows

According to the preliminary results of a new U.S. study, the vaccine for whooping cough commonly administered to young children begins to lose its effectiveness after three years.
The results come from a survey of 15,000 children in Marin County, Calif., where an outbreak of the bacterial disease, also known as pertussis, killed 11 infants and infected more than 8,000 people in 2010, AFP reports.
"When we first started having a pertussis outbreak, we assumed that this would be primarily in the unvaccinated population," Dr. David Witt of Kaiser Permanente Medical Center in San Rafael, California, said, according to AFP. "What we pretty quickly identify is that the bulk of the outbreak was in fully vaccinated children (in the eight-12 age group). Older kids and younger kids seemed to be pretty well protected but the age of eight to 12 was the vast bulk of the cases. And when we examined that, it was correlated to being more than three years from the last vaccine booster dose."
Witt cautioned that more research was necessary as he presented the preliminary results at the Interscience Conference on Antimicrobial Agents and Chemotherapy organized by the American Society of Microbiology.
The children with a vaccine at least three years old were up to 20 times more likely to become infected than those whose last booster injection was more recent, AFP reports. Witt still insisted that parents should get their kids vaccinated as it provided good protection for the first two or three years and seemed to mitigate the symptoms of those who became infected.
Whooping cough causes coughing fits that last up to 10 weeks and can be fatal, especially in infants. It is treated with antibiotics. There are 30 to 50 million cases of the disease worldwide and it kills approximately 300,000 per year, according to the Centers for Disease Control and Prevention.