Abstract
Vaccine surveillance programs are crucial for the analysis of the vaccine's safety profile and the guidance of health policies. The Epidemiological Observatory of the Italian Apulia Region carried out an active surveillance program of adverse effects following immunization (AEFI) after the first dose of the measles-mumps-rubella-varicella (MMRV) vaccine, finding 462 AEFIs per 1000 doses, with 11% rated serious. Applying the World Health Organization (WHO) causality assessment algorithm, 38 serious AEFIs/1000 enrolled were classified as 'consistent causal associations' with MMRV immunization. Severe hyperpyrexia, neurological symptoms and gastrointestinal diseases occurred in 38, 20 and 15 cases/1000 enrolled, respectively. A projection of such AEFIs in an Italian birth cohort would give tens of thousands of serious AEFIs. These incidence data are much greater than the incidence of serious AEFIs reported by the Italian Medicines Agency (AIFA) for years 2017 and 2018, mainly based on passive (or mixed) pharmacovigilance. In a previous epidemiological study in the same Italian Region, during an eight year passive surveillance, the reporting rate of serious AEFI was 0.06/1000 doses, and no cases of febrile seizures were detected applying the WHO algorithm. Taken together, the data suggest that passive pharmacovigilance is utterly inadequate to document the real incidence of serious AEFIs and that current methods of assessing causality may be questioned. Active surveillance programs are required in representative population samples, with results presented separately from those of spontaneous reporting, and causality assessment should be performed carefully and using a correct technique for AEFIs presenting as complex and multifactorial diseases, like those with serious neurologic disorders.
Highlights
Adverse events following immunization (AEFIs) are normally detected by various methods, starting from the preclinical and clinical studies required for product registration and extending to passive or active post-marketing surveillance on samples of the population
Keywords Measles-mumps-rubella-varicella vaccine, MMRV, Pharmacovigilance, Active surveillance, World Health Organization (WHO) Guidelines for causality assessment, Vaccine safety, Adverse events following immunisation, adverse effects following immunization (AEFI)
A causality assessment is conducted on the adverse events recorded, mostly using the algorithm proposed by World Health Organization (WHO), to discriminate whether an event is related to vaccination or independent
Summary
1. Arthur Brawer, Drexel University, Philadelphia, USA Robert Wood Johnson Medical School, New Brunswick, USA. 2. James Lyons-Weiler , The Institute for Pure and Applied Knowledge, Pittsburgh, USA. Any reports and responses or comments on the article can be found at the end of the article. Keywords Measles-mumps-rubella-varicella vaccine, MMRV, Pharmacovigilance, Active surveillance, WHO Guidelines for causality assessment, Vaccine safety, Adverse events following immunisation, AEFI
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