Getty Images
A booster shot may be required to protect teens and young adults from the mumps, new research suggests.
"We need to ensure that they've had two doses of vaccine," Shelley Deeks, a medical epidemiologist at the Ontario Agency for Health Protection and Promotion and lead author of the study, said in an interview.
"My take-home message would be that if you've had only one dose of the mumps vaccine, it's not enough, especially if you're going to a college or university, or playing on a sports team," she said.
The research, published in Tuesday's edition of the Canadian Medical Association Journal, found that outbreaks of the mumps that occurred in Ontario in 2009 and 2010 hit hardest among those born between 1980 and 1996.
A mumps vaccine first became available in 1969 but, until 1980, the disease circulated quite widely in the community so most people developed natural immunity.
In 1996, it became standard to give babies two doses of the measles-mumps-rubella vaccine.
Dr. Deeks said that has left a middle group - young adults who received no vaccination or a single dose of MMR - who are now susceptible to mumps.
There have been numerous outbreaks of mumps across Canada in recent years, notably on university campuses, at the Vancouver Olympics, and this past winter in the snowy playground of Whistler.
Mumps, a once-common childhood illness, is caused by a virus. It is highly contagious and spreads easily through airborne droplets of saliva, which is why it occurs frequently among highly sociable groups like young adults who "share spit" through close contact on the dance floor, the hockey rink, sharing of utensils and so on.
The new research examined outbreaks of the mumps that occurred in Ontario between September, 2009, and June, 2010. In that period, there were 134 people in the province with confirmed mumps - 72 per cent of them male and 59 per cent of whom were 15 to 24 years of age.
Dr. Deeks and her team studied the vaccination history of those who contracted mumps. They found that only 28 per cent had received two doses of the mumps vaccine, 55 per cent had received only one dose and 14 per cent had not been vaccinated at all.
"Clearly, a lot more of the unvaccinated and under-vaccinated are getting the disease," she said.
As part of the study, the research team reviewed 50 outbreaks worldwide and found that the effectiveness of a single dose of the MMR vaccine ranged from 73 to 91 per cent, compared with 91 to 95 per cent for two doses.
Mumps infects the salivary glands, which are located just below the ears, and the most noticeable sign of infection is when those glands swell.
In rare instances, mumps can have severe complications such as meningitis, a life-threatening swelling of the brain.
In adult males, about one third of those who contract the mumps also suffer from painful swelling of the orchitis (testicles) and this can cause sterility.
"In adults, mumps is something that should be taken seriously," Dr. Deeks said.
Because of outbreaks, many universities and colleges now demand that students ensure they have had two doses of mumps vaccine.
Ontario, like a number of other provinces, has also launched a mumps vaccination catch-up campaign that targeted students in postsecondary institutions, but uptake has been poor.