“In general, we have not recommended boosters because there is no clear evidence that people need it. But there probably is very little downside to the booster, so I know people who have gotten it. There is no evidence that titer levels necessarily correlate with whether you are protected or not.”

People who were vaccinated against measles as a child are considered less likely to become infected with the highly contagious respiratory illness. Vaccinated adults who face greater exposure to measles, such as some health care professionals, may consider getting a booster.

With the elevated risk of contracting measles, some people are now wondering if their vaccines are working to protect them from this contagious virus -- or if they need another vaccination on top of the shots they may have already gotten.

More than 250 cases of measles have been reported in the U.S., nearly all of which have been associated with three outbreaks, according to the Centers for Disease Control and Prevention. In light of the rise in cases,