Astrogenetix took advantage of that fast-growing, super-active state to home in on the salmonella genes responsible for infectiousness, and then removed said genes to create a weak vaccine strain.

Verification of the vaccine strain: After its preparation, the hybrid virus needs to be tested to make sure that it truly produces the outer proteins of the pandemic strain, is safe and grows in eggs.

Manufacturers have still had to produce the usual “trivalent” vaccine for this year’s seasonal flu, plus a wholly different vaccine for the more deadly H1N1 strain.