This is interesting, about how flu vaccines are created —

Five flu vaccines are available this year - which one should you get?:

Since the 1950s, the most common way flu vaccines are made is by growing the virus in embryonated chicken eggs.

When the United States experienced an egg shortage recently, with avian influenza partly to blame, the appeal of alternative vaccine-manufacturing processes became clear.

Cell-based vaccines - grown in mammalian cells instead of eggs - are the way of the future, according to Turner.

Are they more effective? Again, no randomised trials compare the efficacy of egg-based and cell-based vaccines, but some studies have shown the latter to be slightly better at preventing illness.

Also interesting:

In healthy adults, data collated by Te Whatu Ora suggests the level of protection against confirmed influenza is between 59-66 percent.