A combination of people not getting vaccinated and a change to how the vaccine was made could be contributing to the spread of a new strain of Whooping Cough.

Early on, the whooping-cough vaccine was considered an unambiguous success story. Over time, though, scientists—as well as crusading vaccine skeptics—raised concerns about the shots’ side effects, which could include high fever and, occasionally, seizures. In the late nineteen-nineties, the U.S. switched to a new formulation, made not from dead, whole cells of bacteria (as the original had been) but from selected components of the bug that would trigger an immune response more safely. Unfortunately, though, the effectiveness of the updated vaccine waned far faster than the old version had, and faster than researchers had expected. This is probably the main reason that whooping cough has surged recently in older children: those who received the newer vaccine as babies became vulnerable again as the doses that they received between ages four and six, and the boosters that they received between eleven and twelve, wore off. (Parents who refuse to vaccinate their children undoubtedly make the problem worse.)

via The Awl