The measles outbreak is growing across the country, and Americans should expect to see more cases for some time, Vanderbilt University School of Medicine's Dr. William Schaffner told CNBC Thursday.
"Measles is so highly contagious and there are sufficient unvaccinated children, we are going to see more for a while," Schaffner, chairman of preventative medicine at the university, said in an interview with "Power Lunch."
The measles outbreak started at Disneyland and has grown to 95 cases across 14 states, with 84 of those cases occurring Jan. 1 to Jan. 28, according to the Centers for Disease Control. This year's number is already more than the median number for most years since 2000.
The CDC said 67 of the total cases are linked to the Disney park.
"People don't really realize how serious this disease is," said Schaffner, also the former president of the National Foundation for Infectious Diseases. "Before we had vaccines in the United States, each year 400 to 500 children died, I say died, of measles and its complications. This is not a disease you should fool with,
After the measles vaccine was introduced, the disease was nearly wiped out from the U.S.
"However, if there are lots of unvaccinated children, as there are now, measles can be imported from abroad, get into those populations and then spread," he said.
Children don't typically receive the first of two doses until they are 12 months old. While it is not widely recommended to give the vaccine earlier, he said if the epidemic continues some pediatricians in affected areas may decide to do just that. However, he noted that children who are vaccinated before their first birthday would still have to receive two more doses.
As for adults who have received the two-dose measles series, there is no need for a booster.
"The protection is strong and should be lifelong."
—The Associated Press contributed to this report.