Dave: Our immune system weakens with age. After about 75 or 80 we're pretty much open season to the bugs out there.

Norbert: So, I've still got fifty years.

Dave: Norbert, your picture's on our website.

Norbert: Oh yeah... but wait! A new study shows I'm as good as I was in my twenties when it comes to a specialized class of immune cells.'My body's cellular immunity, which kills virus-infected cells, remains just as active today.

This is significant because some vaccines, such as the flu vaccine, don't trigger cellular immunity when maybe they should. Instead, the flu vaccine triggers antibodies which studies now show don't work as well in older people since they don't produce enough of them. An antibody is a protein that attaches to viruses and virus-infected cells to mark them for elimination. Whereas cellular immunity involves T-cells that kill infected cells and memory T-cells which recognize a reinfection. We assumed these cells also declined with age.

To test that presumption, researchers took blood from people infected with one of three types of viruses: West Nile virus and two common herpes viruses. After dividing the people into three age groups, researchers measured the numbers and activities of their T-cells, specifically ones called CD8+T cells that kill viruses. Surprisingly, the over-60 group produced the same number of these immune cells compared to the under-40 group.

It suggests older people could benefit more from vaccines if manufacturers changed them to stimulate cellular immunity. That's possible by switching from a dead to a live-weakened virus. There is a live-flu vaccine that appears to be effective, but for now, it's not approved in the U.S. for people over 50.