Viral iatrogenic contamination and safety of biologicals.

The use of biologicals such as bacterial or viral vaccines have an inert risk as a result of their preparation. In the last century it was difficult to determine the correlation of the clinical accidents until the characteristic viral genome became available. Generally, the frequency of accidents provoked by viral vaccines has diminished due to (1) the improvements of the methods used for viral inactivation and purification, (2) the introduction of good manufacturing practices and rigorous regulatory policy and (3) the progress in the post-clinical surveillance of adverse reactions after vaccine administration, allowing a better risk-benefit analysis.