From the Guidelines
Flu vaccine side effects typically start within 6-12 hours after receiving the vaccination and can last for 1-2 days. Common side effects include soreness, redness, or swelling at the injection site, low-grade fever, headache, muscle aches, and fatigue. These reactions are usually mild and resolve on their own within 1-3 days. For most people, taking acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) can help manage these symptoms. Apply a clean, cool washcloth to the injection site if it's sore or swollen. These side effects are actually a sign that your immune system is responding to the vaccine and building protection against influenza viruses. They do not mean you've gotten the flu from the vaccine, as flu shots contain either inactivated virus or only specific proteins from the virus. If you experience severe symptoms like high fever, difficulty breathing, hives, or symptoms that last longer than a week, contact your healthcare provider as these could indicate a rare allergic reaction or another issue requiring medical attention.
Key Points to Consider
- The most frequent side effect of vaccination is soreness at the vaccination site, affecting 10%--64% of patients, and typically lasts <2 days 1.
- Systemic reactions, such as fever, malaise, myalgia, and other systemic symptoms, occur infrequently and most often affect persons who have had no exposure to the influenza virus antigens in the vaccine 1.
- Immediate -- presumably allergic -- reactions, such as hives, angioedema, allergic asthma, or systemic anaphylaxis, occur rarely after influenza vaccination 1.
- The interpretation of these findings should be made with caution given the small number of children studied 1.
Management of Side Effects
- For most people, taking acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) can help manage symptoms.
- Apply a clean, cool washcloth to the injection site if it's sore or swollen.
- If you experience severe symptoms, contact your healthcare provider as these could indicate a rare allergic reaction or another issue requiring medical attention.
From the Research
Flu Vaccine Side Effects
- The provided studies do not specifically mention the timing of flu vaccine side effects 2, 3.
- However, it is known that the flu vaccine can cause side effects, but the studies do not provide information on when these side effects start.
- The studies focus on the importance of vaccination, vaccine composition, and challenges associated with vaccine uptake, as well as diagnosis, management, and prevention of influenza 2, 3.
- They also discuss the need for annual vaccination and the availability of different types of vaccines, including inactivated, live attenuated, and adjuvanted vaccines 3.
- Additionally, the studies highlight the importance of prompt diagnosis and early initiation of antiviral treatment for persons at increased risk for influenza complications 2, 3.