A new FDA study examined the safety of that flu vaccine among U.S. adults aged 65 years and older. The self-controlled case series compared incidence rates of anaphylaxis, encephalitis/encephalomyelitis, Guillain-Barré Syndrome (GBS), and transverse myelitis following 2022–2023 seasonal influenza vaccinations (i.e., any, high-dose, or adjuvanted) in risk and control intervals among Medicare beneficiaries aged 65 years and older.
The researchers reported in the journal Vaccine that among 12.7 million vaccine recipients, 76 anaphylaxis, 276 encephalitis/encephalomyelitis, 134 GBS, and 75 transverse myelitis cases were observed.
“Only rates of anaphylaxis were elevated in risk compared to control intervals,” the authors pointed out. “With all adjustments, an elevated, but non-statistically significant, anaphylaxis rate was observed following any (IRR [incidence rate ratios]: 2.40, 95% CI: 0.96-6.03), high-dose (IRR: 2.31, 95% CI: 0.67-7.91), and adjuvanted (IRR: 3.28, 95% CI: 0.71-15.08) influenza vaccination; anaphylaxis IRRs were 2.54 (95% CI: 0.49-13.05) and 1.64 (95% CI: 0.38-7.05) for persons with and without concomitant vaccination, respectively.”
The study concluded that rates of encephalitis/encephalomyelitis, GBS, or transverse myelitis were not elevated following 2022–2023 seasonal influenza vaccinations among older U.S. adults, although “there was an increased rate of anaphylaxis following influenza vaccination that may have been influenced by concomitant vaccination.”
The CDC advised that inactivated and recombinant influenza vaccines may be administered concurrently or sequentially with other live or inactivated vaccines, and the CDC also noted that injectable vaccines given simultaneously should be administered at separate anatomic sites.
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