The United States is now wrestling with the largest whooping cough outbreak in decades.
Now, a new study offers evidence the newer and safer form of the vaccine -- that's been in use since the 1990s -- may be a major part of the problem.
According to the New England Journal of Medicine, protection weakens dramatically just a few years after a child gets the last shot, around age 6.
The odds of getting whooping cough, also known as pertussis, increased 42 percent per year after children received their fifth and final vaccine.
In light of the findings and earlier, similar research, health officials are considering changes. They include: another booster shot for children, strengthening the vaccine or creating a brand new one.
Dr. John Segreti, an infectious disease specialist at Rush, agrees.
"No vaccine is perfect," said Dr. Segreti. "We probably do need a better vaccine, but that takes a lot of time and money, and that is not going to happen overnight. In the meantime, we have to work with what we have and try to figure out the best way of making what we have work as well as it can."
Current guidelines say kids don't need a booster until they are 11. That could soon change.