Pertussis (whooping cough) cases have been rising for the past few decades in the United States, despite vaccination rates topping 94% in children.
With such high vaccine coverage, we would expect to see pertussis cases dropping instead of rising — so what is going on?
A recent scientific review has concluded that the less-toxic acellular pertussis vaccine (the “aP” in “DTaP”) that was licensed in the U.S. in 1996 is not working as well as expected, which would explain why pertussis is spreading among populations with high vaccine coverage.
The older versions of the vaccine (“DTP” or “DTwP”) contained whole-cell pertussis instead of acellular pertussis. This vaccine is no longer used in the U.S. because it was more likely to cause side effects.
The scientific review of evidence over the last 20 years suggests that the bacteria that causes pertussis, B. pertussis, began evolving to evade the DTP vaccine shortly after it was introduced in 1949.
By the time the acellular version of the vaccine was licensed in 1996, the pertussis strains circulating in the U.S. were no longer as closely matched to the pertussis antigens in DTaP vaccines given to children.
This raises concern about whether vaccine coverage can compensate for the fundamental limitations of the vaccine. According to the lead author of the study, Dr. Christopher Gill, infectious disease specialist and associate professor of global health at Boston University:
“This disease is back because we didn’t really understand how our immune defenses against whooping cough worked, and did not understand how the vaccines needed to work to prevent it. Instead we layered assumptions upon assumptions, and now find ourselves in the uncomfortable position of admitting that we may made some crucial errors. This is definitely not where we thought we’d be in 2017.”
Pertussis, also known as “whooping cough,” is especially serious for newborns and babies. The tiny airways in their lungs can easily become clogged with sticky mucous that the body produces in response to the toxins of the B. pertussis bacteria. The disease can last for several months and often requires treatment in a hospital.