Assessment of potential adverse events following the 2022-2023 seasonal influenza vaccines among U.S. adults aged 65 years and older

Xiangyu Chianti Shi; Joann F Gruber; Michelle Ondari; Patricia C Lloyd; Pablo Freyria Duenas; Tainya C Clarke; Gita Nadimpalli; Sylvia Cho; Laurie Feinberg; Mao Hu; Yoganand Chillarige; Jeffrey A Kelman; Richard A Forshee; Steven A Anderson; Azadeh Shoaibi

doi:10.1016/j.vaccine.2024.04.051

Assessment of potential adverse events following the 2022-2023 seasonal influenza vaccines among U.S. adults aged 65 years and older

Vaccine. 2024 May 31;42(15):3486-3492. doi: 10.1016/j.vaccine.2024.04.051. Epub 2024 May 3.

Authors

Affiliations

¹ Acumen LLC, Burlingame, CA, USA. Electronic address: xshi@acumenllc.com.
² U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Joann.Gruber@fda.hhs.gov.
³ Acumen LLC, Burlingame, CA, USA. Electronic address: mondari@acumenllc.com.
⁴ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Patricia.Lloyd@fda.hhs.gov.
⁵ Acumen LLC, Burlingame, CA, USA. Electronic address: pduenas@acumenllc.com.
⁶ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Tainya.Clarke@fda.hhs.gov.
⁷ Acumen LLC, Burlingame, CA, USA. Electronic address: gnadimpalli@acumenllc.com.
⁸ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Sylvia.Cho@fda.hhs.gov.
⁹ Acumen LLC, Burlingame, CA, USA. Electronic address: lfeinberg@acumenllc.com.
¹⁰ Acumen LLC, Burlingame, CA, USA. Electronic address: mhu@acumenllc.com.
¹¹ Acumen LLC, Burlingame, CA, USA. Electronic address: ychillarige@acumenllc.com.
¹² Centers for Medicare & Medicaid Services, Washington, DC, USA. Electronic address: Jeffrey.Kelman@cms.hhs.gov.
¹³ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Richard.Forshee@fda.hhs.gov.
¹⁴ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Steven.Anderson@fda.hhs.gov.
¹⁵ U.S. Food and Drug Administration, Silver Spring, MD, USA. Electronic address: Azadeh.Shoaibi@fda.hhs.gov.

PMID: 38704258
DOI: 10.1016/j.vaccine.2024.04.051

Abstract

Background: While safety of influenza vaccines is well-established, some studies have suggested potential associations between influenza vaccines and certain adverse events (AEs). This study examined the safety of the 2022-2023 influenza vaccines among U.S. adults ≥ 65 years.

Methods: A 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 ≥ 65 years. We used conditional Poisson regression to estimate incidence rate ratios (IRRs) and 95 % confidence intervals (CIs) adjusted for event-dependent observation time and seasonality. Analyses also accounted for uncertainty from outcome misclassification where feasible. For AEs with any statistically significant associations, we stratified results by concomitant vaccination status.

Results: Among 12.7 million vaccine recipients, we observed 76 anaphylaxis, 276 encephalitis/encephalomyelitis, 134 GBS and 75 transverse myelitis cases. Only rates of anaphylaxis were elevated in risk compared to control intervals. With all adjustments, an elevated, but non-statistically significant, anaphylaxis rate was observed following any (IRR: 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.

Conclusions: Rates of encephalitis/encephalomyelitis, GBS, or transverse myelitis were not elevated following 2022-2023 seasonal influenza vaccinations among U.S. adults ≥ 65 years. There was an increased rate of anaphylaxis following influenza vaccination that may have been influenced by concomitant vaccination.

Keywords: Adverse events; Anaphylaxis; Concomitant vaccination; Influenza vaccine; Vaccine safety.

MeSH terms

Aged
Aged, 80 and over
Anaphylaxis / epidemiology
Drug-Related Side Effects and Adverse Reactions / epidemiology
Female
Guillain-Barre Syndrome / chemically induced
Guillain-Barre Syndrome / epidemiology
Guillain-Barre Syndrome / etiology
Humans
Incidence
Influenza Vaccines* / administration & dosage
Influenza Vaccines* / adverse effects
Influenza, Human* / epidemiology
Influenza, Human* / prevention & control
Male
Medicare / statistics & numerical data
Myelitis, Transverse / epidemiology
Myelitis, Transverse / etiology
Seasons
United States / epidemiology
Vaccination* / adverse effects