Possible Side Effects of Vaccines That You Need to Be Aware Of

Especially in the post-pandemic world that we are now living in, there has been a lot of talk about vaccines, whether or not we should get them and how much research goes into them before they are offered to the public. As with many medications, there are possible known side effects of vaccines, which include short-term flu-like symptoms, but there are also more serious and long-term side effects that are less well-known. These include swelling of the heart and brain damage. While these side effects are not common, it is certainly worth knowing all of the information so you can make an informed decision.

Short-Term Flu-Like Symptoms

The most common after-effects of vaccines are flu-like symptoms. These include contracting a fever, body aches, a headache, nausea, and tiredness. These symptoms might last a day or two and then they will pass. This is nothing to worry about and is quite normal. If symptoms continue past 48 hours, speak to a doctor.

This is the most well-known set of symptoms following a vaccine, however, there are several others that are less spoken about (and less common).


Anaphylaxis is an acute and potentially life-threatening allergic reaction. This is not a common side effect of vaccines but it can happen, which is why sometimes people are asked to wait fifteen minutes after receiving a vaccine before they leave the center. Centers should have epi-pens and antihistamines on site in case of anaphylactic reactions.

Symptoms of anaphylaxis include tightness of the throat, respiratory difficulties, trouble swallowing, nausea, vomiting, diarrhea, stomach cramps, dizziness, fainting, weak heart rate, hypotension, generalized hives, itching, swelling of eyes, lips, mouth or tongue and a feeling of impending doom.

Symptoms typically present themselves fifteen to thirty minutes after receiving the vaccine but can present after several hours.

You should inform the vaccine center before you receive a shot if you have previously experienced anaphylaxis. 

Brain Damage

In some cases, vaccines have been linked to people experiencing complications in the brain, such as encephalitis and encephalopathy. This inflammation of the brain due to viral infection can be very serious and tends to onset between five and fifteen days post-vaccine. 

Both of these neurological conditions linked to vaccines such as the measles, mumps, and rubella shot have several red flags to look out for. The most notable are sudden mood changes, progressive memory loss, exhaustion, and loss of cognitive function. These are all signs of possible brain damage from vaccines. However, as stated above, experiencing these symptoms does not automatically mean you are suffering from brain damage! Please see a doctor if you think this could be affecting you but be aware that there are other potential causes.

Heart Inflammation

A rare but serious potential side effect of vaccines that have been recorded around the world is heart inflammation known as myocarditis or pericarditis. This has been reported mostly in young men but there is yet to be sufficient evidence definitively linking the inflammation to vaccines. Generally, people recovered after a few days of rest and simple treatments.

Signs of myocarditis include stabbing pain or tightness in the chest that might spread across the body, shortness of breath during light exercise, difficulty breathing while resting, flu-like symptoms (tiredness, high temperature, fatigue), and abnormal heart rhythm.

However, remember, if you experience any of these symptoms, do not panic. They can all be symptoms of minor illnesses and do not necessarily mean you have myocarditis! See a doctor as soon as you can and remain calm.

Swollen Neck or Armpit Glands

This is not a common side effect of vaccines, but some people have experienced swelling in the neck or armpit glands on the same side as the arm in which they received the shot. Known as lymphadenopathy, this swelling of the lymph nodes can be confused with breast cancer. However, it is a normal reaction of the body to the injection because your lymph nodes are attempting to fight off potential infection.

Generally, nodes will return to normal over the following weeks. If the lymph nodes stay swollen or get harder, you should see a doctor, as this might be a sign of illness unrelated to the vaccine. If you are due to go for a routine mammogram and you are experiencing swollen neck or armpit glands, you should mention that you have recently had a vaccine when you attend. 

So, Why Do People Get Vaccinated?

Well, there are several positive effects of vaccines such as the Covid-19 shots. These positive effects include reducing your risk of infection and preventing the spread of the virus to others. Both of these things can save lives.

Moreover, people get their children vaccinated against terrifying diseases such as meningitis and tuberculosis to prevent them from losing their family members to preventable illnesses. These vaccines also help to keep the spread of such diseases at bay. For instance, in the UK they no longer recommend the tuberculosis vaccine for everyone as the disease has diminished so much over time it is no longer necessary.

This has been a short list of some of the possible side effects of vaccinations that you need to be aware of before attending your appointment. Knowing the possible side effects, even the extremely unlikely ones, can help you to react quickly and seek medical advice if symptoms do occur following a vaccine.

We have covered the common side effects of flu-like symptoms (nausea, fever, body aches, tiredness, and headaches), but also some less common but more serious and/or long-term potential side effects.

You could experience anaphylaxis, an allergic reaction that causes the throat to tighten among other symptoms. Moreover, there have been some cases of reported brain damage and heart inflammation following vaccination. Swollen lymph nodes are also a possibility.

We looked at why people get vaccinations. They certainly save lives, diminish the spread of dangerous diseases and protect our children. There are also certain pitfalls and dangers, but it is the case with other medications as well. So, before you make a decision about vaccination, look at all of the facts.

Vivek is a published author of Meidilight and a cofounder of Zestful Outreach Agency. He is passionate about helping webmaster to rank their keywords through good-quality website backlinks. In his spare time, he loves to swim and cycle. You can find him on Twitter and Linkedin.