Via CBC News: Flu shot effectiveness for 2015-16 disappointing, data shows. Excerpt:
Experts used to believe the annual flu shot protection was much higher, around 70 to 90 per cent. But not anymore. Those early estimates were based on industry-funded clinical trials that were extrapolated to apply across all ages and flu seasons.
"It was a blanket assumption that is simply not true," [Dr. Danuta] Skowronski said.
That assumption changed dramatically, after Skowronski and colleagues developed a protocol that revealed the true picture of vaccine efficacy. It's called the test negative design (TND) first piloted in Canada in 2004.
"The test negative design has opened our eyes to all kinds of variables that we were blind to for years. We were flying blind," said Skowronski.
The TND system tracks people who show up with flu-like symptoms at several hundred doctors' offices across Canada. Doctors take a sample from every patient for lab testing. They also record whether the person got the flu shot. That simple protocol reveals how often the flu shot fails.
In April, The Lancet published a meta-analysis of test negative design studies, now used globally, and cited Canada as the pioneering group.
"Our public health goal is to minimize the serious health problems association with the flu," said Skowronski. "There's no use promoting a vaccine that isn't working well. The only way you can do better is to recognize the problem in the first place."
This year's data also shows that only about a third of Canadians got the flu shot, about five per cent less than last year.
"That's not a surprise coming out of a year where effectiveness was so low. That had to have an impact," said Skowronski.