As people age, their immune systems tend to weaken. A new high-dose flu shot could offer more protection, but some infectious disease experts say the vaccine isn’t effective enough to justify the cost of public coverage in Canada.

Fluzone High-Dose, manufactured by Sanofi Pasteur, contains four times the amount of antigens compared to a regular flu shot and protects against three common flu strains. Approved for people 65 and older, the idea is that the higher dose will help seniors mount a better immune response and be better equipped to fight off the flu.

But in B.C. and Quebec, health officials have declined to cover the new high-dose flu shot, citing the high cost of the vaccine and what experts there describe as lackluster evidence Fluzone High-Dose is much better than the standard dose.

Danuta Skowronski, epidemiology lead of influenza and emerging respiratory pathogens at the BC Centre for Disease Control, said the benefits don’t justify the price.