Side Effects of Influenza Vaccine in the Elderly
The influenza vaccine in elderly adults is remarkably safe, with only mild local soreness at the injection site lasting up to 2 days being the most common side effect; systemic symptoms like fever, malaise, and myalgias occur no more frequently than with placebo. 1
Common Side Effects
Local Reactions:
- Local soreness at the injection site is the most frequent side effect, typically lasting up to 2 days 1
- This reaction is generally mild and not disabling 1
- High-dose vaccines are associated with higher rates of mild side effects compared to standard-dose vaccines, though they remain well-tolerated 2, 3
Systemic Reactions:
- Systemic symptoms including fever, malaise, and myalgias may begin 6-12 hours after vaccination 1
- These symptoms typically last 1-2 days 1
- Critically, these systemic symptoms occur no more frequently than with placebo administration 1
Rare but Serious Adverse Events
Allergic Reactions:
- Rare immediate allergic reactions can occur in patients with egg hypersensitivity, as the vaccine is grown in eggs 1
Guillain-Barré Syndrome:
- Guillain-Barré syndrome was clearly associated only with the 1976 swine influenza vaccine 1
- This complication has not been associated with influenza vaccines since 1976 1
Critical Safety Context
The Vaccine Cannot Cause Influenza:
- The vaccine does not contain live virus and cannot lead to clinical influenza infection 1
- The vaccine virus is inactivated (made noninfectious), so it is impossible to develop influenza from vaccination 1
- This is a common misconception that limits vaccine uptake, but concern about this side effect is unfounded 1
High-Dose Vaccine Considerations
For adults ≥65 years, high-dose or adjuvanted vaccines are preferentially recommended and demonstrate superior efficacy 1, 4:
- High-dose vaccines show no protocol-defined serious adverse events in clinical trials 3
- While associated with higher rates of mild side effects compared to standard-dose vaccines, they remain well-tolerated 2, 3
- The enhanced protection outweighs the minimal increase in mild local reactions 3
Clinical Implications
Risk-Benefit Analysis:
- The side effect profile is exceptionally favorable, especially when weighed against the substantial mortality reduction (45-68%) and hospitalization reduction (50%) that vaccination provides in elderly adults 1, 5, 6
- Few preventive interventions match the safety profile and clinical benefits of influenza vaccination in this population 5
Common Pitfall to Avoid:
- Do not allow patient concerns about "getting the flu from the vaccine" to prevent vaccination—this is physiologically impossible with inactivated vaccines 1