Small number of cases The cases reported to the authorities responsible for pharmacovigilance are mostly related to a decrease in the effectiveness of Beyfortus, the National Medicines Safety Agency notes in a follow-up report on Monday, September 30.
The Medicines Agency (ANSM) has not identified “any specific risk factor” with Beyfortus, an antibody-based treatment against bronchiolitis in infants offered for a year to parents of newborns, according to its first adverse-effect monitoring assessment, published on Monday.
Between September 11, 2023 and April 30, 2024, 244,495 doses of Bifortus were delivered to maternity wards and in the city, and 198 pharmacovigilance cases, including 153 cases considered “serious,” were declared during this period, ANSM noted in Notification on September 11, 2023 and April 30, 2024. First preventive immunization campaign 2023/2024.
Only 198 cases out of more than 240,000 doses
“The vast majority (74.7%) of the 198 cases reported in pharmacovigilance reported efficacy or ineffectiveness of Bifortus with the onset of respiratory syncytial bronchiolitis in children who received the antibody,” the agency detailed.
She added: “No specific risk factor has been identified in these children who developed bronchiolitis, with varying degrees of severity (without death), after taking Bifortus.”
The ANSM also reported, in its pharmacovigilance report, “three sudden deaths” with no established causal relationship with Bifortus. She points out that in the first case, “there is still (…) suspicion of a possible link to befortus even if risk factors for sudden death have been identified.”
In the second case, “it is very unlikely that there is a direct effect of Bifortus because the effect occurs 79 days after injection”, and in the last case, “the chronology is hardly consistent with the possibility of attributing Bifortus”, which cannot be ruled out.
Nirsevimab, the name of the active molecule, is not a vaccine, even an injectable one, but a prophylaxis that prevents the main virus that causes bronchiolitis, respiratory syncytial virus (RSV), from infecting the organism.
The National Psychiatric Agency also noted that “cases of respiratory disorders and systemic effects after injection have been reported (such as influenza syndrome, decreased appetite, decreased muscle strength), all with positive results.” “An isolated case of stroke has also been reported,” she noted, but explained that “at this stage, the causal relationship between Bifortus and these effects has not been proven.” In total, “21 notable cases” were reported.
Overall, “these results, together with studies on efficacy, confirm the positive benefit-risk balance of Beyfortus against bronchiolitis,” the agency ruled.
