"They don't make the population immune, but they buy you time, either by preventing influenza from getting into the community or slowing down the spread, " Markel said.

CNN: Scientists dig for lessons from past pandemics

Diabetics who are infected with TB become ill with the disease at three times the ratio of the general population because their immune systems are compromised, said Dr. Seaworth, who is also a professor of medicine at the University of Texas Health Science Center-Tyler.

WSJ: TB's Global Resurgence Amplifies U.S. Risk

It is hoped this combination will stimulate the immune system to recognising and destroying cancer cells, while at the same time preventing rapid re-population by any cells not killed off by the immune defences.

BBC: New trial targets kidney cancer

Also, says Bocchini, this is a new strain of flu, and no one in the population would be expected to be immune.

CNN: Swine Flu: A guide for parents