What exactly does the COVID-19 vaccine do to the body?

mRNA vaccines (Pfizer-BioNTech or Moderna) contain material from the virus that causes COVID-19 that gives our cells instructions for how to make a harmless protein that is unique to the virus. After our cells make copies of the protein, they destroy the genetic material from the vaccine.
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Are long term side effects possible with COVID-19 vaccination?


Serious side effects that could cause a long-term health problem are extremely unusual following any vaccination, including COVID-19 vaccination. The benefits of COVID-19 vaccination outweigh the known and potential risks.

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How does the COVID-19 vaccine boost your immune system?

Vaccines work by stimulating your immune system to produce antibodies, exactly like it would if you were exposed to the disease. After getting vaccinated, you develop immunity to that disease, without having to get the disease first.
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How do mRNA COVID-19 vaccines work?

Currently vaccines for COVID-19, the disease caused by the SARS-CoV-2 coronavirus, are the only authorized mRNA vaccines. These vaccines use mRNA that directs cells to produce copies of a protein on the outside of the coronavirus known as the “spike protein”.
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What are the some of the common side effects of the COVID-19 vaccine?


Pain, redness, or swelling where the injection was given; headache; muscle or COVID-19 Vaccine joint pain; fever of 100.4°F (38°C) or higher; chills; upset stomach, throwing up, or diarrhea; swollen or tender glands; or feeling tired or unwell. Most side effects have been mild.

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How Would COVID Vaccines Work in Your Body (English, captioned)



What are the common side effects of the Pfizer-BioNTech COVID-19 vaccine?


Commonly reported side effects in the clinical trial included injection site pain (sore arm), redness and swelling, fatigue, headache, muscle and/or joint pain, chills, fever, swollen lymph nodes, nausea and decreased appetite.

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What are the common side effects of the Moderna COVID-19 booster vaccine?


The most commonly reported side effects by individuals who received a booster dose of the Moderna COVID-19 Vaccine after completion of a two-dose primary series were pain, redness and swelling at the injection site, as well as fatigue, headache, muscle or joint pain and chills.

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Is there a live virus in the mRNA COVID-19 vaccines?

The mRNA vaccines do not contain any live virus. Instead, they work by teaching our cells to make a harmless piece of a “spike protein,” which is found on the surface of the virus that causes COVID-19. After making the protein piece, cells display it on their surface.
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How long has the mRNA vaccine been around?

mRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus (CMV). As soon as the necessary information about the virus that causes COVID-19 was available, scientists began designing the mRNA instructions for cells to build the unique spike protein into an mRNA vaccine.
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Are mRNA COVID-19 vaccines safe?


mRNA vaccines are safe and effective.
mRNA vaccines have been held to the same rigorous safety and effectiveness standards as all other types of vaccines in the United States.

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Does your immune system get stronger after COVID-19?


Any time you catch a virus and recover from the illness, you retain antibodies. These antibodies help your body fight off future infections so that you either don't get sick or have milder symptoms.

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How long does it take for immunity to wane after receiving the COVID-19 vaccine?


A study published by the U.S. Centers for Disease Control and Prevention found that immunity against severe COVID-19 begins to wane four months after receiving a so-called "booster" third dose of the Pfizer or Moderna vaccines.

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Do people who have had COVID-19 have more side effects with the vaccine?

If you had COVID-19 before being vaccinated, the first injection may cause more noticeable side effects than for people who have not had the coronavirus. If you have never had COVID-19, you may notice more side effects after the second dose than after the first dose.

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Does having fever, body pain, and swollen lymph nodes after the COVID-19 vaccine mean I am sick?

These symptoms do not mean you are sick. They signal that your immune system is responding to the shot and building up protection against the coronavirus.

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What are some potential lingering symptoms after COVID-19?


For people who have had COVID-19, lingering COVID-19 heart problems can complicate their recovery. Some of the symptoms common in coronavirus “long-haulers,” such as palpitations, dizziness, chest pain and shortness of breath, may be due to heart problems — or, just from having been ill with COVID-19.

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Who developed the mRNA technology for the COVID-19 vaccine?


Two Penn researchers, Katalin Karikó, PhD, and Drew Weissman, MD, PhD, invented messenger RNA (mRNA) technology that serves as the foundation of the Pfizer/BioNTech and Moderna vaccines.

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Do mRNA COVID-19 vaccines cause heart inflammation?


These cases typically occur in male adolescents and young adults after the second dose, and within a week of vaccination. It is important to seek medical care if symptomatic (chest pain, shortness of breath, having a fast beating, fluttering, or pounding heart).

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Are there any safety concerns concerning mRNA technology of the Pfizer-BioNTech COVID-19 Vaccine?

FDA does not have specific safety concerns with a vaccine that utilizes this technology.

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Can you get the mRNA COVID-19 vaccine if you are allergic to the ingredient in the vaccine?

If you are allergic to an ingredient in a COVID-19 vaccine
If you have had a severe allergic reaction or an immediate allergic reaction—even if it was not severe—to any ingredient in an mRNA COVID-19 vaccine, you should not get either of the currently available mRNA COVID-19 vaccines (Pfizer-BioNTech and Moderna).

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Can the Moderna COVID-19 vaccine cause allergic reactions?

There is a remote chance that the Moderna COVID-19 Vaccine could cause a severe allergic
reaction. A severe allergic reaction would usually occur within a few minutes to one hour after
getting a dose of the Moderna COVID-19 Vaccine. For this reason, your vaccination provider
may ask you to stay at the place where you received your vaccine for monitoring after
vaccination. Signs of a severe allergic reaction can include:
• Difficulty breathing
• Swelling of your face and throat
• A fast heartbeat
• A bad rash all over your body
• Dizziness and weakness

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What are the severe allergic reactions to COVID-19 mRNA vaccines?


“Overall, severe allergic reactions to COVID-19 mRNA vaccines, including life-threatening anaphylaxis reactions such as low blood pressure and difficulty breathing, are rare, on the order of five cases per million vaccine doses administered,” noted Dr. Guerrerio.

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Is it normal that I feel worse after second COVID-19 shot?


This is normal and expected, but it doesn't happen to everyone. Even if you feel worse after the second shot, the side effects should still resolve within a few days.

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Is it normal that I feel tired after taking the Pfizer COVID-19 booster?


The most common AEs included pain at the injection site (23.5%), fatigue (9.7%), and malaise (7.2%) (Table 2). Most of the respondents (67.8%) reported that their general feeling after the booster was similar to the feeling after the second dose; 18.7% and 11.1% reported a milder or worse response, respectively.

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Is the Pfizer COVID-19 vaccine safe?


Pfizer-BioNTech COVID-19 Vaccine Ingredients. All COVID-19 vaccine ingredients are safe. Nearly all of the ingredients in COVID-19 vaccines are ingredients found in many foods – fats, sugars, and salts. The Pfizer-BioNTech COVID-19 vaccine (COMIRNATY) also contains a harmless piece of messenger RNA (mRNA).

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Why do people who had COVID-19 have a strong reaction to the vaccine?


The next time you encounter the pathogen, these responses will kick in faster and stronger, because your immune system is already primed to recognise and respond to it. This is why people who have already recovered from COVID-19 may experience more of these mild reactions.

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