Health officials in B.C. are advising young people to get a flu vaccine after determining that the H1N1 influenza strain, which circulated during the global pandemic in 2009, has returned to become the predominant strain this flu season.

Young children and people with chronic health conditions are especially vulnerable and should get their flu shot now, said Dr. Danuta Skowronski, a flu expert with the BC Centre for Disease Control.

"The H1N1 virus will appear to most people like the regular flu. Most people will recover. But hospitalizations and death are possible and with H1N1 that's most likely for young people with chronic conditions," Skowronski told CBC News.

Skowronski says H1N1 was a "minor player" in flu strains over the last several years, but this year it has made a comeback.

Public health officials say they aren't expecting the same kind of reaction to the flu strain because people have developed a level of immunity since 2009. In B.C., officials estimate about half the population has some protection.

Skowronski says this year's flu vaccine does offer protection against the H1N1 strain. She says it's too soon to quantify the effectiveness of the vaccine, though she expects it will be similar to last year's 60 per cent effectiveness, which is average.

Skowronski says the virus is constantly changing so doctors will continue to monitor how the virus is changing as they plan a vaccine for next year.

"This virus is in its fifth year of circulation, so we should expect mutations," she said.

With files from the CBC's Steve Lus