While measles hasn’t spread to Maine this year despite numerous outbreaks in other parts of the country – primarily in New York City and Washington state – some adults, especially those in their 30s, 40s and early 50s, are wondering whether they need a measles booster shot.

When the measles vaccine (now called MMR for protection against measles, mumps and rubella) was first introduced in the 1960s through the early 1990s, it was only given as one dose to infants. A measles outbreak in the late 1980s caused scientists to take another look at vaccine effectiveness, and recommended a booster.

Since the mid-1990s, children have been routinely given an MMR booster shot around age 5, following the initial vaccine given between 12-15 months.

Adults who have only had one dose of the vaccine are still protected from the viral infection, but at a slightly lower rate. One dose provides 93 percent protection, while two doses ramps up vaccine protection to 97 percent, according to the U.S. Centers for Disease Control and Prevention.

The CDC recommends that for adults who are unsure about their vaccination status to order a test – called a titer – that will tell whether their bodies have immunity to measles. Also, adults who had only one dose as a child who are attending college, work in the health care field or travel internationally are recommended to receive the booster shot, the CDC said.

Adults who contracted measles before the vaccine became widely available in the 1960s are also immune and do not need an immunization.

Those who are unsure can get tested or be re-vaccinated at their primary care doctor. Being re-vaccinated will do no harm, said Dr. Kolawole Bankole, director/administrator of Portland Public Health.

“For adults, it is very important to know where you are at. You need to know whether you are protected against the measles,” Bankole said.

Meanwhile, Maine lawmakers are currently debating whether to tighten the requirements for school-required vaccines, as the return of vaccine-preventable diseases continues at record-setting levels. Maine has one of the highest opt-out rates in the nation for schoolchildren entering kindergarten, at 5.6 percent in 2018-19.

Measles cases in the United States hit a 25-year high through April 26, according to the CDC, with 704 cases in 22 states. The measles outbreaks have been most acute among unvaccinated populations in Washington state and New York City.

The last reported measles case in Maine was one confirmed case in 2017. On April 2, the Maine CDC reported a measles exposure by a Massachusetts resident who had visited the Skin Clinic in Falmouth and the Maine Centers for Healthcare Endoscopy in Westbrook on March 27, but so far there have not been any reported cases in Maine from that exposure.

Dr. Rhianna Meadows, medical director at Nasson Health Care in Sanford, a low-cost clinic, said that Maine is likely more susceptible to measles in the summer, when tourists arrive from many parts of the United States and the world.

“York County would be one of the first places affected,” Meadows said. “In the warmer months, people are coming and coming, where in the winter, it’s mostly Maine people staying put.”

Meadows said for adults who don’t know what shots they received in childhood, and can’t find out, she recommends getting tested to see if they are immune. If not, Nasson Health Care would give both shots, she said.

The measles outbreaks have spurred many public health actions, including mandatory vaccinations in New York City.

There are pockets of dangerously low vaccination rates that make the return of preventable diseases more likely. Forty-three Maine elementary schools had at least 15 percent of parents forgoing vaccines for children entering kindergarten by using the non-medical philosophic and religious exemptions.

Measles is a highly contagious and dangerous disease, with symptoms that include a rash that can cover the entire body, fever, cold, cough, runny nose and red, watery eyes.

After an infected person leaves a location, the virus remains alive for up to two hours on surfaces and in the air. The incubation period is typically 10 to 14 days, but can be as long as 21 days. Measles is so contagious that over 90 percent of people who are exposed and not vaccinated or immune from previously contracting measles will get the disease.

Measles can cause severe health complications that may include pneumonia, encephalitis, brain damage and possibly death.

In about one in 1,000 childhood measles cases, death can occur, and there’s a similar chance that children can become deaf or have permanent brain damage from the measles.

Before the measles vaccine became widely available in the 1960s, about 3 million to 4 million children in the United States contracted measles each year, with 48,000 hospitalizations and 400 to 500 deaths, according to the CDC. Measles was declared eradicated in the U.S. in 2000, but people deciding not to vaccinate their children has led to its resurgence in recent years.