8 Myths about COVID-19 Vaccines Debunked

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Anesthesiologist Anoushka Afonso receiving a COVID-19 vaccine.

MSK anesthesiologist Anoushka Afonso receives a COVID-19 vaccine from clinical nurse Janine Guerra.

Now that COVID-19 vaccines from Pfizer-BioNTech and Moderna have been authorized by the US Food and Drug administration and are rolling out to protect people at greatest risk of infection, we want to dispel some common myths about the vaccines.

Myth: The COVID-19 vaccines were approved too quickly. We don’t know enough about whether or not they are effective.

Truth: COVID-19 vaccines were developed rapidly compared with earlier vaccines because scientists, doctors, and government agencies all over the world invested massive resources to cut red tape and publish results as soon as they were available.

Because we are in the middle of a pandemic, many people were available and willing to participate in clinical trials to help test the safety and effectiveness of the vaccine. The Pfizer-BioNTech clinical trial involved more than 40,000 people; the Moderna trial had more than 30,000 volunteers.

Those clinical trial results were scrutinized by an independent group of experts before the US Food and Drug Administration (FDA) reviewed the data and then granted Emergency Use Authorization.

The trials showed that the Pfizer-BioNTech vaccine is 95% effective and the Moderna vaccine is 94% effective at preventing COVID-19.

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Myth: We don’t know whether or not the COVID-19 vaccine is safe. It could be more dangerous than contracting COVID-19.

Truth: As a result of clinical trials, we now have data from tens of thousands of people showing that these vaccines are safe. The regulatory agencies and independent scientific experts that have reviewed the results have followed very strict guidelines for determining safety as well as effectiveness.

Some people have mild to moderate side effects, but they don’t last long — about one to three days. The most common side effects include soreness at the injection site, fatigue (feeling tired), headache, aches, and fever. They are more common after the second dose, and you might need extra rest. Severe side effects are rare and treatable. Experts at the FDA and the Centers for Disease Control and Prevention are still monitoring trial participants — and will continue to monitor them — as well as members of the general public who get the vaccine.

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Myth: People with underlying health conditions, including cancer, should not be vaccinated.

Truth: Based on clinical trial data, doctors at MSK believe the COVID-19 vaccines are safe and could offer significant protection for people with cancer. This is important because those with cancer may be at higher risk for complications from COVID-19.

MSK recommends that most people with cancer, regardless of the type of treatment they are receiving, get the vaccine. If you are a current patient or recently finished cancer treatment, you should discuss getting the vaccine with your care team.

COVID-19 Vaccines Safety and Effectiveness
Learn from MSK infectious disease specialist Elizabeth Robilotti on what you need to know about the two COVID-19 vaccines.
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Myth: If you’ve already had COVID-19, you don’t need to get the vaccine.

Truth: We don’t yet know how long people who have already had the virus will be protected against getting infected again. There have already been some cases of people developing COVID-19 a second time. For that reason, MSK recommends getting the vaccine even if you have had COVID-19.

Both drug trials included participants who had already had COVID-19, and it was found to be safe in them.

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Myth: One shot of the vaccine is enough.

Truth: Both the Pfizer-BioNTech and Moderna vaccines require two shots about three to four weeks apart, and it’s important that you get both of them. If you don’t get the second shot, you will not be fully protected from infection.

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Myth: You can get COVID-19 from the vaccine.

Truth: The vaccine does not contain any part of the virus, either live or inactivated. Instead, it contains genetic material called messenger ribonucleic acid (mRNA), which tells your body to make a protein, or antigen, that will teach your immune system how to recognize the virus. That way, you’ll be ready to fight it if you are exposed.

The COVID-19 vaccine will not cause you to test positive with a COVID-19 test, but you may test positive on some antibody tests. If you do, that means the vaccine has helped your body to create antibodies against the virus.

What’s Different About Messenger RNA (mRNA) Vaccines for COVID-19?
Learn what is different about the messenger RNA vaccines that protect against COVID-19.
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Myth: The mRNA in the COVID-19 vaccine will alter my genetic code.

Truth: Both the Pfizer-BioNTech and Moderna vaccines use mRNA technology. The mRNA that is injected into your body does not interact with your DNA. Your cells will break down the mRNA and clear it from your body as soon as it has finished making the necessary antigen.

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Myth: After you get vaccinated, you don’t need to wear a mask or distance yourself from other people.

Truth: The vaccine protects you from getting sick. However, experts still don’t know if it’s possible for you to carry and transmit the virus to another person after you have been vaccinated. So it’s important to continue wearing a mask, wash your hands often, and stay at least six feet apart from people who don’t live in your household.

We expect that when 70% of the population has received the vaccine, we will reach what is called “herd immunity,” meaning the chances of the virus still circulating are very low. At that point, public health experts will advise the public that preventive measures can be relaxed. That could take months or years, depending on how many people get vaccinated.


January 12, 2021


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