5 Reasons Why You May Be Feeling Unwell After the Flu Vaccine
With the COVID-19 pandemic, getting the flu shot is more important than ever. However, a common concern and question that gets asked is: can the flu shot give you the flu? This is a myth that unfortunately causes a lot of people to resist getting their yearly flu vaccination. The answer is that no, the flu shot does not give you the flu.
The flu vaccine is created to protect us from getting sick from influenza, which is a highly contagious respiratory infection. It works by triggering the production of antibodies that protect the body from the flu virus. While the flu shot does contain live influenza viruses, they are weakened to the extent that it won’t actually give you the flu. So why then may you still feel unwell after getting the flu shot?
Five common explanations for why you may feel like the flu shot gave you the flu are:
Full immunity didn’t develop
Once you have received the flu shot, it takes up to two weeks for the body to achieve full immunity to the virus. Therefore, if you were exposed to the flu around the same time as you got the flu shot, then unfortunately the body wasn’t able to develop immunity before the virus took hold.
The vaccine doesn’t protect against that particular strain
The reason why we need to get the flu shot every year is that influenza mutates and changes each year. Researchers make predictions and develop the vaccine based on the strain they believe will be affecting people that particular year. However, it is impossible to protect against every strain and it could be that you have been infected with a strain not protected by the vaccine.
It could be the side effects of the flu shot
Because the vaccination does still contain the live influenza virus, it is very common for it to trigger some unpleasant side effects or symptoms which could be mistaken as a light version of the flu. These side effects can include nausea, fever, headaches, fatigue, or sore muscles.
You are sick with something else
The flu shot only provides a defence against influenza and not other common respiratory illnesses, such as the cold. Therefore, you could be suffering from a bad cold which coupled with some side effects of the flu shot could easily be mistaken for the flu. However, symptoms of a cold should not be too severe so if you are still feeling unwell after a week you should see a doctor.
You are age 65+
Unfortunately, the flu shot is less effective for this age group due to their immune responses being lower. This is important to be aware of as older individuals are considered to be at higher risk of complications from influenza. In fact, research from the Centers for Disease Control and Prevention found that 70-85% of flu-related deaths and 50-70% of hospitalizations occurred in this age group. Therefore, even with the flu shot being less effective, it is still recommended as the best defence against the virus.
Discover how influenza differs from COVID-19 and how to tell the difference.