Health experts have called for the suspension and withdrawal of Moderna’s mRNA influenza vaccine, mFLUSIVA, following reports of adverse reactions, including cases involving severe weakness, temporary loss of mobility, hospitalisation and other medical complications.
The concerns emerged from an analysis of the US Vaccine Adverse Event Reporting System (VAERS), jointly managed by the Food and Drug Administration (FDA) and the Centres for Disease Control and Prevention (CDC).
According to the analysis, 78 adverse event reports involving mFLUSIVA were recorded in September and October, less than three months after the vaccine received FDA approval in August.
The data, covering reports submitted up to October 30, showed that two cases were formally classified as serious, although several others described potentially significant medical conditions.
Among the reported cases were two individuals who temporarily lost the ability to walk following vaccination.
A 71-year-old man reportedly experienced shaking in his arms and weakness in his legs less than 24 hours after receiving the vaccine, leaving him unable to walk. The case was flagged as involving a disability.
Another report involved an 84-year-old woman who reportedly developed severe weakness and became unable to stand within an hour of receiving the injection.
Other reports included a patient hospitalised with fever and low oxygen levels, as well as a 76-year-old man who experienced hallucinations after receiving mFLUSIVA alongside Moderna’s COVID-19 vaccine, Spikevax.
Internal medicine physician, Dr Clayton J. Baker, described the reported reactions as concerning, pointing to cases involving high fever, debilitating fatigue, severe body aches and cardiovascular complications.
An analysis of 58 reports containing information about the onset of symptoms found that 51 cases involved reactions occurring on the day of vaccination or the following day.
Baker argued that the timing raised questions about a possible connection between the vaccine and the reported injuries. However, adverse event reports alone do not establish that vaccination caused the conditions.
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The analysis also found that 37 of the 78 reports involved individuals who received a COVID-19 vaccine around the same time as mFLUSIVA. Thirty reportedly received both injections on the same day, while seven received them on different dates. Two reports also mentioned an RSV vaccine.
Moderna’s mFLUSIVA, also known as mRNA-1010, was approved in August for adults aged 50 and above.
Brian Hooker, chief scientific officer of Children’s Health Defense, described the number of reports recorded within two months as unusually high, particularly given the vaccine’s limited initial rollout.
Epidemiologist Nicolas Hulscher of the McCullough Foundation also questioned the safety profile, arguing that the number and nature of the reported reactions warranted further investigation.
Concerns have also been raised about the vaccine’s clinical trial findings.
Hulscher, who co-authored a reanalysis of the clinical trial data published in the Journal of Independent Medicine, said the study identified higher rates of severe adverse reactions among mFLUSIVA recipients compared with participants who received conventional influenza vaccines.
According to the reanalysis, severe systemic reactions occurred in 5.5 per cent of mFLUSIVA recipients, compared with 0.9 per cent among those receiving comparator vaccines.
The researchers also reported 23 deaths of unspecified causes in the mFLUSIVA group, against nine in the comparator group.
An FDA briefing document reportedly acknowledged higher rates of serious adverse events and more deaths of unspecified causes among mFLUSIVA recipients, although the agency identified no major deficiencies in the clinical trial data.
The vaccine’s regulatory approval also followed earlier disagreements within the FDA over whether Moderna’s clinical trial met the required standards for licensure.
Experts have further questioned the absence of specific clinical trial evidence on administering mFLUSIVA alongside COVID-19 vaccines, despite public health recommendations encouraging simultaneous vaccination during the flu season.
Immunologist and biochemist Jessica Rose argued that the use of similar lipid nanoparticle technology in mRNA flu and COVID-19 vaccines could be relevant to investigating the reported adverse events.
However, the available VAERS reports do not establish causation, and the reported cases require further scientific and regulatory assessment.
Despite these limitations, several experts believe the findings justify an urgent review of the vaccine’s safety.
Hulscher called for the immediate suspension and removal of mFLUSIVA from the market, arguing that the reported clinical trial findings and post-approval safety reports raise serious questions about its risk-benefit profile.
Other experts have similarly urged the FDA to investigate the reports and reconsider the vaccine’s approval.