Measles outbreak may be ‘time bomb,’ doctor warns

Vaccinated adults could still be vulnerable

As Canada deals with its worst measles outbreak in recent years, experts say adults vaccinated against measles decades ago aren’t all as bulletproof as they may believe.

Infections are occurring in people who were immunized, suggesting that their immunity has waned. Short of doing expensive blood tests on everyone, there is no way of knowing who is at risk.

“There’s sort of a ticking time bomb here: how many of these people exist, we don’t know, and who they are, we can’t identify them,” said Dr. Brian Lichty, associate professor in the division of molecular medicine at McMaster University in Hamilton.

B.C. is in the midst of its worst measles outbreak on record, with at least 230 confirmed cases reported to the Public Health Agency of Canada and many more under investigation.

Meanwhile, cases have been reported in Alberta, Ontario, Saskatchewan and Manitoba. Most of the cases have been linked to travel to countries where measles is endemic or circulating widely, such as the Philippines and the Netherlands.

The Canadian Paediatric Society recently warned that while most Canadian children are immunized on time, as many as 20 per cent of parents delay immunizations or outright refuse recommended vaccines.

Some parents have become fearful of vaccines because of fraudulent, discredited studies linking the shots with autism and other health scares, Lichty said.

A re-emergence of measles isn’t the only threat. “We’re starting to see not just measles outbreaks but rubella outbreaks,” he said. Rubella, also known as German measles, can cause severe birth defects.

He believes the vast majority of adults who were vaccinated when immunization programs rolled out in most jurisdictions decades ago are protected against measles.

But different people respond differently to vaccines. Some don’t produce enough antibodies to the virus.

In 2011, there were 750 cases, almost all — 725 — occurring during an outbreak in regions of Quebec.

“I think we’re reaching statistically the point where we’re going to start seeing deaths,” Lichty said.

ALLEN MCINNIS /THE GAZETTE Despite widespread vaccination programs, medical experts fear that some adults may not be sufficiently resistant to disease like measles or rubella — both of which have recently seen fresh outbreaks.