LITTLE ROCK, Ark. (KTHV) -- Arkansas Department of Health is once again urging the public to get a mumps booster shot. This is after the number of cases in the state has exceeded 1,600.

However, the MMR vaccine may not be as effective as the experts once believed.

In Northwest Arkansas, and across the country, people are getting their MMR booster shot to protect themselves from the mumps, but doctors say that shot, like the flu shot of 2014, isn't a match for the mumps that they're seeing.

"It's not turning a corner; it is continuing to get worse," said Dr. Dirk Haselow, ADH’s state epidemiologist.

He said this week the number of mumps cases in Arkansas has broken 1,600.

"I think people have heard a lot about this, and they may begin to tune it out. That's the last thing we want to have happen. We want people to be aware this is going on, and they continue to take it seriously," Haselow explained.

The ADH, as well as the Center for Disease Control, is taking this outbreak very seriously, holding vaccination clinics in the northwestern part of the state.

The problem they're now facing is that many of the children that are testing positive for mumps have been vaccinated.

"We are actually to the point that we are worried that this vaccine may indeed not be protecting against the strain of mumps that is circulating as well as it could," Haselow said, explaining the ADH knows the vaccine is working somewhat, because more people haven't been infected. And those who are infected, aren't as sick as they could be.

"With the number of people we've seen infected, we'd expect three of 400 cases of orchitis, or swollen testicles in boys, and we've seen five."

Why can't the CDC develop a new MMR vaccine, for the strain we are seeing now? Well, Haselow said it's not that easy.

"It has to go through some rigorous testing. Typically a vaccine candidate takes about five years to take to the public."

The MMR vaccine is about 88% effective, but Haselow recommended everyone be up to date. Many Arkansans are heeding that warning.

"We've had several adults who have come in to get their booster shot," said Lisa Roberts, a nurse at the Shot Clinic in Little Rock. She said that they have seen a slight increase in the number of patients asking for MMR boosters.

"Most of them are adults who haven't gotten a booster shot. The MMR vaccine usually lasts 15-20 years, on average, but at that point, it kind of starts depleting. So, people want to get in and get that booster."

The state has lost quite a few immunization records, so you may have a hard time finding out if you're fully vaccinated. The good news is you can't over-vaccinate for the mumps.