Why and when you should get the flu shot

The overall effectiveness of the flu shot depends, in part, on getting the timing right, says a University of Alberta infectious diseases expert.

"In most people, the flu shot is about 50 to 60 per cent effective when the vaccine is well-matched with the flu virus type that is circulating," said Lynora Saxinger, who works as a physician at the U of A hospital.

Although that's not as high as we'd like, getting the shot also reduces your risk of serious complications if you still catch a virus, she added. "As well, higher vaccination rates are associated with less severe epidemics, which helps protect those who can't get the vaccine or who have a weakened immune system."

And while research studies do suggest that some people respond better to the vaccine than others, we are not yet at the stage where we can predict the individual odds of a good response in a practical way, said Saxinger.

"In general, those most at risk of severe illness-small kids, elderly persons and immunocompromised-tend to have less good response. However, as there is no risk of infection from the vaccine itself, the best odds are to get the shot and consider early treatment with antivirals in the high-risk patients if they get influenza anyway."

According to Alberta Health Services, during the 2016-17 flu season, over 1.1 million Albertans received flu shots, or roughly 25 per cent of the population. The flu vaccine is available province-wide this year beginning Oct. 23.

Should I time my shot for when flu season peaks?

Unfortunately, there is no way to predict exactly when flu season will peak, said Saxinger.

"It varies from year to year. In 2009, it peaked in late October. In 2015, it peaked in February," she said. "And if you wait too long, you might get caught in the epidemic wave without getting the shot. So far, it seems to be an early start already and there are suggestions it may be a bad influenza year, based on the epidemics in the southern hemisphere."

Bottom line: Everyone should consider getting vaccinated when the shot becomes available to reduce the strength of the epidemic, said Saxinger. "The flu shot and good hand washing are simple ways to help protect yourself, and others who are more vulnerable. It's also safe and recommended in pregnant women, to protect the mom from influenza infection and protect the baby after birth. Vaccination may also reduce the risk of preterm birth and fetal death," she added.

And if you forget or get too busy? "It can be offered late in the season as long as the person hasn't had clinical influenza-not a cold-already," she said. "There's often a second peak of cases towards the end of the season so it's still worthwhile."

Symptoms of influenza include severe cough and fever, as well as aches and fatigue, which can lay people low for days, said Saxinger. The symptoms are are usually more extreme than that of a cold, which don't result high fevers and more likely feature a runny nose, she added.

"Antibodies produced by the shot usually persist for about a year."

But doesn't the vaccine wear off more quickly in the elderly?

One study suggested in some patients, primarily persons 65 years and older, the flu shot's effectiveness may wane by the end of season.

"While delaying vaccination might permit greater immunity later in the season, deferral could result in missed opportunities to vaccinate, as well as difficulties in vaccinating a large number of people within a more limited time period," explained Saxinger.

Vaccination programs need to find the right balance between ensuring maximum vaccine-induced protection while avoiding leaving it too late or vaccinating too long after the influenza virus circulation begins, she added. In other words, get the flu shot when it's offered by your provincial health authority.

"Revaccination later in the season of people who have already been fully vaccinated is not recommended."

Can I still use nasal spray vaccines for my needle-phobic child?

Yes, you can, but Saxinger said it's best to only use the live virus nasal spray vaccine if your child is so afraid of needles, he or she wouldn't otherwise get immunized.

"While U.S. data suggest nasal spray vaccines weren't effective in kids, data from Canada, United Kingdom and United States Department of Defence data sets suggest it was up to 50 per cent effective. So it's been categorized as an option only."

The nasal spray flu vaccine is only available at pharmacies for a fee.