While major pharmaceutical companies around the world race to prepare a swine flu (H1N1) vaccine in anticipation of a possible outbreak this fall, many issues regarding the vaccine’s safety have yet to be resolved.

Media outlets report that one major issue revolves around whether the shots will contain an adjuvant, an immune-boosting substance, to stretch the vaccine supply. Adjuvants, according to the Canadian-based Vaccination Risk Awareness Network, may contain harmful chemicals such as mercury (in thimerosal), aluminum and formaldehyde and have been linked to neurological disorders. The Coalition for Sensible Action for Ending Mercury-Induced Neurological Disorders has expressed concerns about these adjuvants and their possible health risks; they state that in a recent public engagement session sponsored by the Centers for Disease Control and Prevention, many questions regarding the vaccine’s safety remained unanswered. The center’s official information is published at cdc.gov/h1n1flu.

Another general concern results from the “fast-track approval” approach for which the pharmaceutical companies are pushing to win the race against time. Clinical trials involving all age groups are currently under way in many countries; the trials do not include pregnant women even though pregnant women are a major vaccination target.

As it stands, the H1N1 swine flu vaccine is classified as a Class C drug, meaning that the vaccine has not yet been evaluated for carcinogenic or mutagenic potential. Nor have animal studies been conducted to investigate possible fetal harm.