evidence: Some vaccines may also contain adjuvants, preservatives, stabilizers and residual byproducts from the manufacturing process. All of these components are safe in the concentrations used in vaccines. Many of them are common and can be found in our bodies, drinking water, food or other products we ingest or use regularly. Adjuvants are substances that help vaccines work better by boosting the body’s immune response. Tiny amounts of aluminum salts, for example, have been safely used for this purpose for decades.