From the Guidelines
Flu vaccines are safe and well-tolerated, with most people experiencing mild side effects that resolve within a few days, and serious side effects like severe allergic reactions are extremely rare, occurring in approximately 1-2 cases per million doses. The most common side effects reported are soreness, redness, tenderness, or swelling of the injection site, as well as mild arthromyalgia, low-grade fever, and nausea 1. These reactions are not the flu itself but rather the immune system responding to the vaccine.
Common Side Effects
- Soreness, redness, or swelling at the injection site
- Low-grade fever
- Headache
- Muscle aches
- Fatigue
Serious Side Effects
- Severe allergic reactions (approximately 1-2 cases per million doses)
- Guillain-Barré syndrome (rare, with some studies suggesting a small increased risk, but others finding no association) 1
Special Considerations
- Individuals with a history of severe allergic reactions to vaccines or egg proteins should discuss this with their healthcare provider before vaccination 1
- Alternatives to egg-based vaccines, such as cell culture-grown and recombinant vaccines, are available for those with severe allergies 1
Management of Side Effects
- Rest
- Drinking fluids
- Taking acetaminophen or ibuprofen (following package instructions) can help manage symptoms
Recommendation
Annual influenza vaccination is still strongly recommended for most people over 6 months of age, as the temporary discomfort from vaccine side effects is a small trade-off for protection against potentially serious illness 1.
From the Research
Flu Vaccine Side Effects
- The flu vaccine can cause side effects, including allergic reactions, pseudo-allergic reactions, and exacerbation of atopic symptoms or vasculitis 2.
- Anaphylaxis is a rare but life-threatening side effect of the flu vaccine, and can occur in individuals without a history of allergic diseases 3, 4.
- The risk of hypersensitivity reactions after influenza vaccination is low, but can be higher in adult females than in males 4.
- Common side effects of the flu vaccine include fever, fatigue, cough, and body aches, but these are typically mild and short-lived 5.
- Acetaminophen can be used to reduce the severity of side effects such as fever and myalgia, without impairing the immune response to the vaccine 6.
- The formulation and production system of influenza vaccines can affect the probability of severe allergic reactions to the vaccine 3.
- Delayed-onset anaphylaxis can occur after influenza vaccination, and can be caused by an IgE response to the vaccine 3.