As the rollout of COVID-19 vaccinations continues, some of your friends and loved ones may experience side effects that seem to imply the vaccine was making them sick. This can create a great deal of anxiety for those who are unsure about the vaccine, but vaccine side effects are a normal part of the body’s defensive response, and symptoms will subside in most people within a few days.

Whenever something unidentified enters the body, the body begins mounting a defensive response to remove the new material. As it attacks the foreign body, your body may experience symptoms that resemble sicknesses that you are being vaccinated against. This is a well-understood phenomenon that often occurs with flu vaccinations, for example. Unlike flu vaccinations, however, the COVID-19 vaccines do not contain live COVID-19 virus bodies. Instead, the vaccines contain protein blueprints that help your body recognize and fight COVID-19 without ever encountering the virus.

What to Expect

Fever, fatigue, and headache are some of the most common side effects of vaccinations. Some people may even develop a cough if inflammation occurs in the lungs. Not everyone will experience these side effects, and there is a potentiality for rare side effects that are more severe. It is essential to talk to your physician or care provider about what side effects you can expect.

As a vaccine enters your body, your body will not differentiate between something helpful and something harmful. It only knows that something new and unexpected is present in your bloodstream and begins producing antibodies to fight and disable the newcomer. Most vaccines do not contain live viruses – And those that do contain weakened or dead viruses. Instead, they contain a piece of a virus that is incapable of causing harm on its own. Your body will still recognize these pieces if it encounters a live version of the virus and will have antibodies ready to go in such an event.

The COVID-19 vaccines being developed do not always include part of the virus, either. Instead, they contain an mRNA sequence – Which is sort of like a blueprint – Which temporarily causes some of your immune cells to produce proteins that resemble parts of the COVID-19 virus. Your immune system will recognize these proteins as foreign and start to mount an immune response despite being produced by your body. Side effects are a sign that your immune system has recognized the “threat” and is forming a reaction against it.

Though this is a relatively new form of a vaccine, the processes behind it are well understood. Even though your body produced parts of the proteins found in COVID-19, it will still recognize those proteins if it encounters wild COVID-19 and more effectively eliminates it.

How to Handle Side Effects

Be ready to call out from work if you begin to feel sick. While the vaccine will not cause you to develop COVID-19, the symptoms can be similar. The CDC advises people not to take acetaminophen (Tylenol), ibuprofen (Advil), or antihistamines (Benadryl) before taking the vaccine. These medicines can mask symptoms you are experiencing and make catching side effects more difficult.


Most side effects will be mild and not require medical attention, and nearly all will subside in a few days. If the shot hurts after being given, administer a cold, clean towel to the injection site, and be sure to exercise and move your arm to prevent it from stiffening up.


If you develop a fever from the vaccine, drink plenty of fluids and wear light clothes. For more information about fevers, see our article here. The same advice applies here. After a fever develops, you can take acetaminophen to reduce your temperature and discomfort.

Contact a Medical Professional

You should call a doctor immediately if you experience shortness of breath or swelling in the face or lips. This can be a sign of an allergic response that does require medical attention. You should also seek attention if the injection site remains red and tender 24 hours after your shot or if any symptoms are beginning to worry you.