With winter on the way, public health officials are reminding Canadians it’s time to think about getting the annual flu shot.

But this year, many parents will face a dilemma about which flu vaccine to give their children: the traditional needle form, or the newer nasal spray that’s easier to administer, but has fallen out of favour in some places.

This year, U.S. flu experts are recommending the nasal mist -- sold as FluMist - not be used because it simply is not effective enough.

And yet, Canada’s National Advisory Committee on Immunization still recommends the spray vaccine, saying Canadian studies show it works.

In fact, on Friday, the Canadian Paediatric Society released its 2017/2018 flu season vaccine recommendations that said healthy kids can opt for either the needle version or the spray.

So why would doctors in the U.S. be advised not to use the spray, while physicians in Canada are told to offer it?

The question is an important one, especially for the many parents whose children hate needles. FluMist vaccine is easier to administer to kids over the age of two, as it is simply sprayed up the nose.

Since FluMist was first brought to Canada in 2010, studies have shown it works as well as the needle version. In fact, beginning in 2011, Canada’s National Advisory Committee on Immunization (NACI) has recommended the spray over the needle for most healthy kids because its ability to ward off the flu was so strong.

But last year, NACI removed its “preferential recommendation” for the spray, saying it no longer believed FluMist’s effectiveness was superior to the needle version.

So which version should parents seek out this year, and why are the recommendations in Canada and the U.S. so different?

Dr. Allison McGeer, who heads infection control at Toronto's Mount Sinai Hospital and is a member of NACI’s Influenza Working Group, says Canadian and American studies on the effectiveness of the nasal flu vaccine have simply had different results.

She says there are three major flu surveillance systems in the U.S., one of which found an issue with the effectiveness of FluMist against an important strain of the flu: H1N1. That problem emerged three years ago and, although FluMist’s manufacturer has tried to tweak the vaccine, its effectiveness in the U.S. has not improved.

But here in Canada, a large study out of Alberta last year tracked which version of flu shots people were receiving and found that “FluMist looked fine,” McGeer said.

It’s not clear why there’s a difference between the Canadian and U.S. results. Health officials in Canada look only at vaccine effectiveness rates in Canada, not the U.S., and our studies show the spray is providing good protection against the flu.

'All the data we have says FluMist is fine'

The bottom line for parents, McGeer says, is that both vaccine forms work and the most important thing is to choose whichever is easiest to access.

“If your child doesn’t care whether they get a needle or a nasal spray, give them the needle this year. It might make you feel more secure,” she said. “But if your child really hates needles, don’t worry about it and get the FluMist. Because all the data we have in Canada says FluMist is fine.”

McGeer says it’s understandable that the U.S. Centers for Disease Control’s Advisory Committee of Immunization Practices (ACIP) would recommend against the spray this year, given their surveillance found it works so poorly.

In fact, their data showed the spray’s effectiveness among kids and teens in 2015/16 was only 3 per cent, meaning it offered “no protective benefit.” In comparison, needle flu shots had a 63 per cent effectiveness estimate. "The reason for the recent poor performance of (FluMist) is not known," CDC officials said at the time.

But Dr. McGeer says it’s important to look at the “confidence limits” in those studies, which she says are “very wide.” That wide margin is a reflection of the difficulty of gathering reliable information about how vaccinated people in the general population fare during flu season.

In the first years FluMist became available, the studies showed the spray performed better that the needle vaccine. “At the time, it seemed like an easy recommendation to say, use the nasal spray,” McGeer said.

But that has changed in the last couple of years. McGeer says, and as more data have become available, “it’s no longer obvious that the nasal spray is better.”

No longer covered in Alta., Sask.

In Alberta, health officials announced in August the province would no longer cover FluMist for kids under its immunization program, though parents can still buy the spray from pharmacies. They made the decision because of “increasing vaccine costs,” short expiry dates, and the fact that the needle version had “similar effectiveness.” They also cited “decreased interest from the public with FluMist.”

Saskatchewan will not be offering FluMist at its public health clinics for the second year in a row.

The spray is still available to children under flu vaccination programs in other provinces, including in Ontario, B.C. and Quebec. (It is also available without a prescription across all Canadian provinces and territories except Quebec, where a prescription is required.)

McGeer says the biggest factor that influences the effectiveness of a flu vaccine is not what method is used to administer it; it’s the number of people who get vaccinated. If enough people are immunized, “herd immunity” will help protect those who can’t be immunized, and that’s what health officials want to see.

“We really want to make getting vaccinated as easy as possible,” Dr. McGeer said. “So, for families with busy lives, my advice is really there’s not much difference between the vaccines. So just get a vaccine -- whichever one is least intrusive to your life.”