Table 1.

Particularities of vaccines.

Particularities	Comments
Mechanism of action	Long-term and persistent immunological effect in one or few doses
Manufacture	High technology requiring strict specifications, batch releases for reproducibility
Indications for use	Mostly in prevention in unaffected subjects according to the official recommendations of national health authorities
Impact of use	At the individual and population level in modifying the pathogen epidemiology
Unusual characteristic	Phase III clinical trials in more important population size than for classic drugs
Unusual population	Administration of vaccine candidates in healthy volunteers (target population) in phase III clinical trials
Post-authorization pharmacovigilance	Larger exposed population of healthy subjects implying an extremely low risk to keep a favorable benefit/harm balance
Unusual benefit-risk ratio	Extremely low risk