The flu shot seems to protect some people better than others because of differences in immune response between ethnic groups, say researchers who hope to better tailor vaccines to an individual some day.

Flu vaccine effectiveness varies depending on how well it matches the strains circulating in a particular year.  Our immune defences also become weaker with age, so seniors are most at risk from flu complications.

Now researchers at Dana-Farber Cancer Institute in Boston have studied stored blood samples from the 1,000 Genomes Project. They've investigated 14 slightly different forms of one gene with an eye to seeing what's more effective at responding to a flu virus.

For example, a higher percentage of African individuals had a form of the gene likely to allow the flu, compared with Asian and European individuals, the researchers found.

Flu immunization

Scientists would like to give patients a flu vaccine best suited to their genetic profile. (Monty Kruger/CBC)

"I didn't expect ethnic background to really play into this," said Dr. Wayne Marasco, a virologist at the cancer institute.

Instead of developing a universal, one-size-fits-all flu vaccine that protects us for decades, the findings suggest a different approach might be needed.

Marasco says he would like to first test the person's blood to understand the genetic makeup of the individual and then choose a flu vaccine from a suite of several. That would mean you would receive the vaccine best matched to your genetic profile.

As chief of clinical and metabolic genetics at Toronto's Hospital for Sick Children, Dr. Ronald Cohn shares Marasco's enthusiasm for the possibilities from this avenue of research.

Needs to be repeated

"I think the fact that you have different ethnic backgrounds based on their genetic variation either responding well or not responding well to the flu virus vaccine is of potential huge significance," Cohn said.

Cohn cautioned the study needs to be repeated in other populations to check if the genetic variation is really as strong as it seems so far.

"The fact that it's only one gene is quite promising, because that will potentially make it easier to implement it clinically," Cohn said.

In the meantime, the findings could help predict whether someone is likely to be protected from the flu vaccine or not.

Marasco called it an entry point in the field of immunology that hasn't been cracked yet.

The study was published last month in Scientific Reports, an open-access journal from the publishers of Nature.