Pertussis (“whooping cough”) is a serious lung infection with the bacteria B. pertussis. Pertussis produces a toxin and sticky mucous that can clog the tiny airways in an infant’s lungs. The disease often last for months and it can be fatal.
Children in the U.S. typically get 5 immunizations with the DTaP vaccine, which protects against diphtheria and tetanus as well as pertussis, before they start kindergarten.
DTaP vaccine coverage in the U.S. is topping 94% of kindergarten-age children, but studies show that pertussis cases continue to rise. With such high vaccine rates, we would expect to see fewer cases of pertussis instead of more — so what is going on?
A new scientific review suggests that the failure of the DTaP vaccine to reduce pertussis rates over the last 20 years may associated with the evolution of the B. pertussis bacteria to evade the vaccine.
Dr. Christopher Gill, lead author of the study and infectious disease specialist and associate professor at Boston University, explained:
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.”
Dr. Gill believes that the B. pertussis bacteria began evolving to avoid the original DTP vaccine shortly after it was introduced in 1949.
The DTP vaccine contained whole-cell pertussis and it is no longer used in the U.S. because it was more likely to cause rare neurological side effects than the acellular pertussis vaccines (the “aP” in DTaP) that were licensed for children in 1996.
The scientific review suggests that by the time the DTaP vaccine was licensed in the U.S., the strains of pertussis that were circulating around the world had evolved, so they were not as closely matched to the pertussis strains in the DTaP vaccines.
As explained by Dr. Gill, “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.”