Given that swine flu vaccines are in short supply ahead of a predicted fall epidemic, U.S. plans to use the vaccines in their raw form, without ingredients to swell supplies, has come under criticism.

The additives, called adjuvents, were recommended by the World Health Organization to increase global supplies of the vaccine.  They also boost immunity by increasing the strength of the antigen by as much as 10-fold.

But the U.S. health department has said that it won’t use adjuvents if it has enough of the antigen supply to vaccinate residents.

“Adjuvent use would be contingent upon showing that it was needed or clearly beneficial,” said Jesse Goodman, acting chief of the Food and Drug Administration on July 17.

The medical journal Lancet criticized the policy in its editorial, saying that it is irresponsible, given the low supplies of vaccine globally. The problem is that H1N1 viruses don’t grow well in eggs, and the strains yield only 30% to 50% of antigen as compared to other flu strains.

The U.S. will test flu adjuvents and “review all clinical data to inform our decision on their potential use,” said Bill Hall, a spokesman for the Health and Human Services Department to Bloomberg News.