It's the time of year when experts crunch the numbers to see how well the flu shot worked. The result? Better than last year, but still not good enough. Just shy of 45 to 50 per cent," said Dr. Danuta Skowronski of the BC Centre for Disease Control, who presented the data to the Global Influenza Vaccine Effectiveness meeting at the World Health Organization last week. In 2014-15, the flu shot offered essentially zero protection against the circulating influenza virus of that season. Back then, the prevailing strain was H3N2. This year's main circulating virus was H1N1. Skowronski said the vaccine was ... disappointing. 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," 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," said Skowronski. Scientists also once again observed [that] people who get the shot with no prior vaccine exposure seem to have better protection than people who get the shot year after year.