After the widespread implementation of the Tdap (Tetanus, Diphtheria, Pertussis) vaccine among children, the U.S. nearly achieved complete eradication of pertussis, better known as whooping cough. But in the past two decades, the number of cases of this highly contagious bacterial disease has been on the rise, according to a new study published in the Proceedings of the National Academy of Sciences. The authors, using computer modeling, demonstrate how the recent uptick is attributable to a loss in “herd immunity,” which is the inhibitIon of person-to-person disease spread that occurs when over 90 percent of a community is immune to a disease.
What does this mean in layman’s terms? Some time ago, when whooping cough was more prevalent, people were exposed to the bacteria more often, thus keeping immunity levels consistently high. After the vaccine — which does not confer lifelong immunity — was introduced in 1981, pertussis became less common and herd, or community, immunity waned because our immune systems were no longer primed with antibodies from repeated, low-level exposure to the bug.
So, in order to retain your body’s immune “memory,” people in their late teens and older should get a Tdap booster shot to continue to protect themselves as well as the children and infants in their vicinity who are more susceptible to the occasionally lethal effects of whooping cough.