Don’t assume you’re immune from measles and mumps

February 23, 2012

Emily Senger

SPECIAL TO THE STAR

Many adults lack the antibodies to fight measles and mumps, even if they got a routine MMR vaccine as children.

While these diseases are rare in Canada, public health officials say adults between 20 and 42 should ensure their vaccines are up to date, particularly if they are thinking of having a child.

“Even though there is very little risk, most diseases tend to be worse in infants, so you just want to protect your baby as much as you can,” says Dr. Shelley Deeks, associate director of surveillance and epidemiology with Public Health Ontario.

Until the mid-’90s, doctors believed one round of the MMR vaccine would ensure protection for life, but they then realized that two doses are required to protect against measles and mumps. Since 1996, children have routinely been given a second MMR vaccine. There was also a catch-up campaign for measles in Ontario that year, where schoolchildren got a second dose of a measles-only vaccine.

Before 1970, these infectious diseases circulated widely, meaning most people born before then developed immunity.

Thus, a gap in immunity exists for some people who were born after 1970 and before 1992.

“Measles is one of the most infectious diseases that we have,” Deeks says. “One person can infect a whole bunch of people.”

Though measles has been considered eliminated in the Americas since 2002, outbreaks have been reported since then. According to a Public Health Ontario report, the largest measles outbreak since then was recently in Quebec, with 764 cases reported between last April 3 and Feb. 8.

In the past decade, Ontario has registered an average of 136 cases of mumps per year, according to a report from Public Health Ontario released in January.

Many of these cases are confined to a community. Last July, for example, Ontario saw a mumps outbreak of 39 cases, some of which were linked to Ki restaurant on Bay Street, where a staff member brought mumps back from a trip to Vancouver, passing it on to other restaurant employees, patrons and workers in surrounding office towers.

There have been targeted mumps vaccine campaigns for health-care workers, military members and students at post-secondary institutions — groups considered at a higher risk for contracting and passing on the disease.

Anyone who is uncertain about their immunity can find out through a simple blood test.

The most important part of the MMR vaccine for women to ensure is up to date before they are pregnant is rubella, says Dr. Elaine Herer, deputy chief of Obstetrics and Gynecology at Sunnybrook Hospital. It can cause defects in the fetus, most commonly deafness. It can also result in miscarriage, particularly in the first trimester.

Rubella is regarded as eliminated in the Americas, which means cases are very rare in Canada and usually associated with foreign travel.

When Toronto ESL teacher Emily Mooney had a mandatory blood test before getting married in Massachusetts in 1997, she was surprised to find she lacked the antibodies to protect against rubella. Even after she received a vaccination, her body didn’t make the antibodies against rubella.

“It was definitely something I was concerned about,” Mooney says. “I tried to stay away from visibly sick people.”

She gave birth to a healthy daughter who is now 5.

The rubella portion of the vaccine requires only a single dose in most cases, but it is possible that a woman will require a booster shot as well, says Herer: “There are just some women who won’t mount enough of a response to show that they have immunity.”

Timing the MMR shot is another issue for women who want to get pregnant and need a booster. Since MMR is a live vaccine, containing small amounts of the viruses, the Society of Obstetricians and Gynecologists of Canada recommends against giving it to women who are already pregnant.

It also recommends that women who have had the MMR vaccine wait at least four weeks before trying to conceive.

For Nancy Polanco, a nursing assistant in Windsor, ensuring up-to-date vaccines was a given when she started planning a second child, a daughter who was born in March 2010.

“Working in a health-care field, I didn’t want to catch anything that I could transmit to the baby,” Polanco says. “I worked up until I was eight months pregnant, so catching something was a huge concern for me.”

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