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The current vaccine for pertussis, or whooping cough, is highly effective during the first three years after children get their shots, but immunity wanes over the next several years, leaving little protection from the disease, researchers have found. In an Ontario study published in the Canadian Medical Association Journal, researchers found that by the time a child is seven or eight years old, the vaccine?s effectiveness has diminished significantly.
?The protection that the vaccine gives is very good in the first couple of years after the immunization is given,? said Dr. Natasha Crowcroft, chief of applied immunization research for Public Health Ontario. ?So it?s good news for protecting babies. But that protection, it fades pretty quickly. So by the time you?re at seven or eight years old, you?ve got very little protection left.? Whooping cough is a highly contagious bacterial infection that affects the respiratory tract and is often marked by a severe hacking cough, followed by a high-pitched intake of breath that sounds like a ?whoop.? Some infants may not cough, but may struggle to breathe or even temporarily stop breathing. The odds of contracting whooping cough following vaccination increased by 27 per cent each year, although the overall risk was still small, the researchers found.
Before the introduction of Canada?s public pertussis vaccine program, annual incidence of the disease averaged 156 cases per 100,000 people. Since the vaccination prog...