A British laboratory may have found a fix for the low yield problem that has been plaguing companies making swine flu vaccine.

The National Institute for Biological Standards and Control says it is ready to ship new versions of its vaccine seed strain to manufacturers as of today.

The lab's principal scientist, John Wood, says early work with the new version of the seed strain shows it generates a virus yield that's on par with what manufacturers get in seasonal flu vaccine production.

Wood cautions that has to be confirmed by manufacturers, but he says he's quietly confident the improved seed strain may fix the yield problem.

Manufacturers had been reporting the first seed strains they worked with produced only about one-third of what they get in seasonal flu vaccine production.

Low yielding seed strains would add to the amount of time it would take manufacturers to fill their pandemic vaccine orders.