RESUMEN
In January 2023, the United States Food and Drug Administration and the Centers for Disease Control and Prevention noted a safety concern for ischemic stroke in adults 65 years of age or older receiving the BNT162b2; WT/OMI BA.4/BA.5 COVID-19 bivalent vaccine. This self-controlled case series analysis evaluated stroke risk among Medicare fee-for-service beneficiaries aged 65 years of age or older receiving: 1) a Pfizer-BioNTech (BNT162b2; WT OMI BA.4 and BA.5) or Moderna (mRNA 1273.222) COVID-19 bivalent vaccine, 2) high-dose/adjuvanted influenza vaccines, and 3) concomitant COVID-19 bivalent vaccines and influenza vaccines, from August 31 to November 6, 2022. The primary analysis did not find elevated stroke risk following COVID-19 bivalent vaccines. In the age subgroup analyses, only the 85+ year age group had a risk of NHS (Incident Rate Ratio (IRR)=1.36, 95% CI 1.09 to 1.69 [1 to 21 days]) and NHS/TIA (IRR=1.28, 95% CI 1.08 to 1.52 [1 to 21 days]) with BNT162b2 Bivalent WT OMI BA.4 and BA.5. Among beneficiaries receiving a concomitant COVID-19 bivalent vaccine and a high-dose/adjuvanted influenza vaccine, an increased risk was observed for NHS (IRR=1.20, 95% CI 1.01 to 1.42 [22 to 42 days]) with BNT162b2 Bivalent WT OMI BA.4 and BA.5 and for TIA (IRR=1.35, 95% CI 1.06 to 1.74 [1 to 21 days]) with mRNA 1273.222. Results of the secondary analyses showed a small increased risk of NHS following high-dose or adjuvanted influenza vaccines (IRR=1.09, 95% CI 1.02 to 1.17 [22 to 42 days]).