Table 2.

Definitions of Vaccine Failure

Confirmed clinical vaccine failure	The occurrence of the specific vaccine-preventable disease in a person who is appropriately and fully vaccinated taking into account the incubation period and the normal delay for the protection to be acquired as a result of immunization. The application of this definition requires clinical and laboratory confirmation (or epidemiological link to a confirmed case, where applicable) that the actual disease is vaccine preventable, i.e. that the pathogen (including, where appropriate, type, subtype, variant, etc.) and clinical manifestations are specifically targeted by the vaccine.
Suspected clinical vaccine failure	The occurrence of disease in an appropriately and fully vaccinated person, but the disease is not confirmed to be the specific vaccine-preventable disease, e.g. invasive pneumococcal disease of unknown serotype in a fully vaccinated person. Applying this definition also requires that the incubation period and the normal delay for the protection to be acquired as a result of immunization have been taken into account.
Confirmed immunological vaccine failure	The failure of the vaccinee to develop the accepted marker of protective immune response after being fully and appropriately vaccinated. This definition requires that there is an accepted correlate or marker for protection, and that the vaccinee has been tested or examined at an appropriate time interval after completion of immunization.
Suspected immunological vaccine failure	The same definition as above except that the time-frame for testing after immunization may be inappropriate and therefore it is difficult to assess vaccine failure.

Definitions taken verbatim from CIOMS/WHO Working Group on Vaccine Pharmacovigilance. Definition and Application of Terms for Vaccine Pharmacovigilance. http://www.who.int/vaccine_safety/initiative/tools/CIOMS_report_WG_vaccine.pdf. 2011. Date accessed: November 28, 2017.”