For hundreds of years bacterial and viral vaccines have been-in a way-bioengineered and were generally well received by the public, the authorities, and the medical profession. Today, additional tools, e.g. molecular biology, enable new approaches to the development of better and safer products. Various vaccines derived from gene technology have now been licensed for commercial use and are acknowledged within the scientific community. Acceptance by the public and the politicians is, however, negatively influenced by the discussions encompassing gene manipulation in man and animals, transgenic plant, and "novel food". Lack of information leads to confusion and fear. Concurrently, the absence of spectacular and life-threatening epidemics limits the perceived value of immune prophylaxis and its benefits. Scientists in institutes and industry are in a position to stimulate acceptability of bio-engineered vaccines by following some simple rule: (1) adherence to the principles of safety; (2) establishment of analytical and control methods; (3) well functioning regulatory and reporting systems; (4) demonstration of usefulness and economic benefits; (5) open communication; and (6) correct and prudent wording.