Every now and then, a virus emerges that captures the world's attention and sparks a rush to create a vaccine to prevent its further spread: think H1N1, Ebola, and now Zika, a flu-like disease with seemingly mild effects but which is currently under investigation for possible links to serious birth defects in cases where pregnant women were infected with the virus.

Such epidemics act as a reminder of the crucial role vaccine research plays in the fight against the spread of . In North America, the alarm that tends to sound around such cases highlights an even deeper truth: have made disastrous outbreaks and epidemics relatively rare.

Potentially deadly infectious diseases that once ravaged Canadian communities - such as measles, polio, and diphtheria, to mention a few - are now all preventable thanks to immunization, which has been called one of the most important advances in public health in history.

Yet, the success of those same immunization programs—estimated to have saved more lives in Canada over the past 50 years than any other health initiative—has also helped spawn one of the most divisive health care debates today: Do we still need vaccines?

"When you don't see devastating diseases around you every day, some—particularly young—parents are saying, 'Well, do I really need my child to get these needles to prevent diseases I'm not seeing?'" explains Joanne Langley, CIHR-GSK Chair in Pediatric Vaccinology in Dal Medicine's Division of Infectious Diseases and associate director of the Canadian Center for Vaccinology, a collaborative partnership between Dal, the IWK Health Centre and the Nova Scotia Health Authority.

Too much misinformation

Dr. Langley says that while it's great to see parents thinking critically about health care and the value of such interventions, doctors often lack the time or resources to offer the kind of collaboration and consultation needed to ensure patients fully understand the benefits of vaccinations.

To fill gaps in their knowledge, some individuals turn to the Internet or media for answers. The problem with that approach, says Dr. Langley, is there's too much information—and much of it lacks medical credibility.

"What we know is that there is a tremendous amount of misinformation, and if you're not able to weed through it, then your understanding of the issue would be distorted by it," she says.

Vaccine hesitancy, as it's referred to in the medical community, can have serious consequences not only for individuals who pass up the chance to be immunized against vaccine-preventable diseases, but also for the community at large. The fewer people who are immunized, the higher the risk that an infection will spread and impact those groups who are unable to protect themselves with vaccination: infants who are too young to be vaccinated, individuals who cannot be vaccinated for medical reasons, and people who may not adequately respond to immunization (the elderly, for example).

Dr. Langley says combatting vaccine hesitancy and strengthening immunization programs can be challenging in Canada as we have a health-care system that tends to favour treatment and acute care over prevention. And while the federal government can provide an overall vision for , it's the provinces and territories that ultimately decide on the delivery of care, which she says can cause problems when it comes to tracking immunization across the country and ensuring equal access to vaccines.

"Some [provinces and territories] are better than others, some have more vaccines than others," she says, "and if you move from province to province, there's no integrated system to see what vaccines you've had."

A national vision

Dr. Langley is among those who have advocated for a national vaccine registry as a way to help coordinate the collection of data around vaccine receipt, improve immunization rates, and help officials prepare for potential outbreaks.

For Dr. Langley, piecing together a more accurate picture of who has been vaccinated and who hasn't is an important step in illustrating the impact of what infectious disease prevention has done for us individually and for the community as a whole.

"Vaccination is really a intervention in the broadest way in that we're not just thinking about our own individual health," says Dr. Langley. "When we are vaccinated, we are playing our general role in keeping the community healthy and protecting the vulnerable."