Whooping cough booster shot may offer only short-term protection

The rapidly fading effectiveness of the pertussis booster vaccine may help explain recent widespread outbreaks of whooping cough, according to researchers. The United States stopped using a whole-cell pertussis vaccine in the 1990s and began using an acellular version called DTaP. Researchers looked at 1,207 pertussis cases among children who had had the acellular vaccine in childhood. They found that when these children got the Tdap booster, it was 69% effective after the first year, then dropped to less than 9% 2 to 3 years later.