But last week, two teams working independently reported a discovery that could help lead to a universal flu vaccine.

VOA: special.2009.03.04

The traditional way to make flu vaccine is to grow the virus in chicken eggs.

VOA: special.2009.11.11

The standard flu vaccine causes the body to produces antibodies, which target parts of the virus that frequently mutate.

VOA: standard.2010.07.21

Drugmakers around the world are rushing to produce the swine flu vaccine by this fall.

FORBES: Market Scan

Authorities earlier had said the flu vaccine was 62% effective for adults and children.

CNN: Flu vaccine less effective, especially among elderly

Generally a flu vaccine is considered pretty good if it's more than 60 percent effective.

NPR: Q&A: Weighing The Value Of Less Effective Flu Shot