COVID-19 Vaccines: Myths and Facts

February 2021

With so much misinformation floating around about COVID-19 vaccines, it can be hard to determine what’s true and what’s not. We’ve compiled some of the most common misconceptions around COVID-19 vaccines and explained why they’re false.

Myth #1: COVID-19 vaccines were made too quickly to be thoroughly tested for safety and effectiveness.

To receive approval or authorization from the FDA, all vaccines must be tested in three sets of trials: phase 1 with a small number of people, phase 2 with hundreds of people and phase 3 with tens of thousands of people. Usually, there are long gaps between these trials because the researchers must wait for funding. With the COVID-19 vaccines, researchers had all the funding they needed from the start, so no delays occurred between trials, making the process much, much faster. However, researchers followed the same protocols in the COVID-19 vaccine trials that are required for all vaccine trials.

The Pfizer vaccine was tested in phase 3 trials with more than 40,000 people, and the Moderna phase 3 trials had more than 30,000 people. These trials were the same size—or larger—than past vaccine trials. And, just as in the past, the FDA waited to authorize the vaccines until enough time had passed after vaccinations to confirm that the data on their safety and effectiveness was strong. The FDA and the CDC reviewed both vaccines in detail before the public began receiving them, and both agencies are continuing to monitor both vaccines’ safety and effectiveness in the general population.

The Pfizer and Moderna vaccines both went through the same extensive testing process for safety and effectiveness as past vaccines approved by the FDA.

Myth #2: People who’ve already had COVID-19 don’t need to get the vaccine.

It’s true that people who have had COVID-19 are unlikely to get it for at least three months after their infection clears because their bodies have protective immunity against the disease. But beyond that, it’s not clear how long the antibodies providing immunity last. With respiratory viruses, including SARS-CoV-2, it’s common for immunity to eventually wear off over time.

While COVID-19 reinfections appear to be rare, it’s also likely that reinfections are being under-counted. In addition, people who had COVID-19 months ago may not be immune to new variants of the disease, such as the one from the U.K., the one from South Africa and any others that develop.  The most effective way to protect against reinfection of COVID-19 is to get one of the vaccines.

Myth #3: The COVID-19 vaccines can cause harmful or long-term side effects.

All vaccines, like all medications, can have side effects. These side effects, or reactions, are a normal part of getting vaccinated. They usually occur because the immune system is responding to the vaccine—which means the vaccine is working. Clinical trials enroll tens of thousands of people so that researchers can learn what all those possible side effects are, including possible severe or rare ones. So far, the vast majority of side effects from the COVID-19 vaccines are typical ones that occur with many other vaccines. Most people experience redness, swelling or soreness at the injection site. The soreness often does not develop until later in the evening or the next day and may last several days.

After injection site reactions, the most common side effects include headache, nausea, muscle stiffness, soreness and aches. A majority of people who received the Pfizer or Moderna vaccine experienced at least one of these effects after the first dose. These symptoms were even more common in people after they received their second dose, especially among people under 65. Another vaccine side effect, fever, was also more common after the second dose, with one in six people experiencing a fever after the second dose. These side effects passed within one to three days.

Anaphylactic reactions—severe allergic reactions—have occurred rarely after both the Pfizer and Moderna vaccines in people who had a history of anaphylactic reactions. Everyone who experienced one was treated and recovered completely. Expect to wait about 15 minutes after you receive your vaccine to make sure you don’t experience an allergic reaction. People with a history of severe allergies to any components of the vaccine should not get it. With nearly all vaccines, any long-term side effects show up within a few weeks or months after vaccination. No long-term side effects have occurred with either vaccine.

Myth #4: People who have been vaccinated against COVID-19 no longer need to wear a mask or social distance.

Both the Moderna and the Pfizer vaccines are extremely effective, reducing the risk of infection by about 95%. That means if 100 vaccinated people were exposed to the virus that causes COVID-19, only five of them might develop the disease. However, sometimes people can develop an infection, where the virus begins to replicate in their body, yet never develop symptoms of the disease. These people may still be able to pass on the virus to others. Many vaccines prevent this from happening, but not all do. So far, scientists are not sure whether the Pfizer or the Moderna vaccines can prevent this. There is good reason to think the COVID-19 vaccines could prevent those kinds of infections, but researchers don’t have enough information yet.

To be on the safe side, it’s important to continue wearing a mask and socially distancing while in public after getting vaccinated to be sure you don’t unknowingly pass the virus to others, especially those who have not yet been vaccinated.

Myth #5: People not at high risk for COVID-19 complications don’t need to get the vaccine.

The people most likely to die or experience long-term effects from COVID-19 are older adults, especially those in their 60s, 70s and 80s, and those with certain underlying conditions. Those conditions include type 2 diabetes, cancer, pregnancy, obesity, COPD and certain heart conditions (such as heart failure and coronary artery disease). However, people of all ages and health statuses can die from COVID-19.

As of February 10, 2021, the CDC reported that more than 10,000 people ages 25 to 44 have died from COVID-19. Those numbers don’t include the tens of thousands of people under the age of 65 who are experiencing serious long-term effects from COVID-19, such as difficulty breathing and extreme fatigue lasting months after infection. An estimated one in 10 people who have COVID-19 develop these long-term symptoms, according to a recent study. Getting the vaccine is the most effective way to avoid becoming one of those statistics.

In addition, even if you catch COVID-19 and experience few symptoms or recover quickly, you are contagious to other people for a few days before any symptoms appear. Researchers don’t know for sure yet whether vaccinations prevent transmission, but new evidence has shown that people who are vaccinated but get infected have very low levels of the virus in their body, so they’re less likely to infect others than those who are not vaccinated.

Myth #6: Getting a COVID-19 vaccine can give me COVID-19.

The COVID-19 vaccines do not contain the SARS-CoV-2 virus that causes COVID-19. That means it’s biologically and physically impossible for the vaccine to cause COVID-19. The Moderna and Pfizer vaccines are mRNA vaccines that contain a tiny strip of genetic material that tells your cells to build one of the proteins found on the SARS-CoV-2 vaccine. After your cells do that, the body recognizes the protein as foreign and builds antibodies against it. The protein itself cannot harm you or cause disease.

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