Efficacy, effectiveness, immunogenicity--are not the same in vaccinology.

Manuscript of Carrera et al is devoted to immunization in inflammatory bowel disease (IBD) that is very important issue in gastroenterology. However, some specific definitions used in the article need clarification. Efficacy of vaccine is measured in a randomised, placebo-controlled studies, that are expensive and difficult to plan. Moreover, it is unethical to offer a placebo instead of vaccine. For all of these reasons, efficacy of vaccine is measured in IBD patients rarely. Effectiveness of vaccine is measured as an epidemiological affect from observational studies. These studies are also uncommon in IBD because it would be difficult to perform a study that assess the prevalence of one rare disease (vaccine-preventable) in patients with a chronic rare condition, such as IBD. Immunogenicity of vaccine refers to the ability of a vaccine to induce an immune response in a vaccinated individual that is, in fact, the matter of the article.