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Which group is a bigger threat to the overall health of Canadians, the devout anti-vaxxers or the partial vaxxers?

The hesitant crowd, because there are more of them, so they have a larger overall impact on herd immunity. The more people are immune, the easier it is to protect everyone. One of the arguments in favour of vaccination is that it doesn’t just protect you, it also protects your neighbours and those who might not be able to get a vaccine because they’re very young or very old or have a compromised immune system. The scientific literature identifies “three C’s” of vaccine hesitancy. Confidence is the amount of trust in the vaccine’s effectiveness and safety, including trust in those who are suggesting vaccines; complacency is the perception of risk — is a vaccine really necessary, in this day and age, in this part of the world? Then there is convenience: location of service, vaccine availability and cost. “Some feel they lack information or have safety concerns, others might find themselves too busy and many are unaware of the risks of infectious disease,” says a 2017 report from the C.D. Howe Institute that explores under-vaccination in Canada.

What are the objections to vaccines?

There are a litany of them. There’s the fear of toxic substances in vaccines, and belief in a “big pharma” conspiracy to sell these drugs to as many people as possible. Still others believe a child’s immune system could be overwhelmed by too many vaccines at too young an age (it will not) or that natural immunity, achieved by being infected and living to tell the tale, is superior. Then there is the classic fear of autism, a belief born from a debunked study by British doctor Andrew Wakefield that said the MMR (measles, mumps and rubella) vaccine causes the developmental disorder. In early March, a study published in the Annals of Internal Medicine of more than 600,000 children confirmed that children who received the measles, mumps and rubella vaccine were not at increased risk of autism. One 2010 Ontario study that looked at who is opting out of vaccines grouped children born in 1997 and earlier, and children born in, or after, 1998 — the year Wakefield’s paper was published in The Lancet. Younger children were much more frequently exempted for “moral,” “conscientious” or “philosophical” reasons. Children exempted for religious or philosophical reasons are 35 times more likely than vaccinated kids to contract measles, the authors reported, “in addition to increasing community risk by upwards of 30 per cent.”