Both the Pfizer and Moderna vaccine require two doses, and it is vital that both does are administered on time. The Pfizer vaccine requires two doses 21 days apart, and the Moderna vaccine requires the doses be administered 28 days apart. The vaccines are not interchangeable, so you must receive the second dose of the same vaccine product as the first dose. The Johnson & Johnson vaccine only requires one dose.
It is very important that you receive your second dose of the COVID-19 vaccine on time. The time-frame between doses is determined by the companies producing the vaccine to maximize your body’s ability to create antibodies against the virus. Many routine vaccines, such as Varicella (chickenpox), also require more than one dose for maximum protection.
Every effort should be made to make sure your second dose is the same vaccine product as the first dose. Studies have shown that the vaccines are safe and work well when the same vaccine product is used for both doses.
We strongly recommend that you get both doses from the same vaccine provider. Doing so ensures that you are getting the same vaccine product for both doses at the right time.
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The FDA requires that vaccines undergo a rigorous scientific process, including three phases of clinical trials, before they authorize or approve the vaccine. The COVID-19 vaccines are subject to the same safety standards as other vaccine trials. To date, the independent Data and Safety Monitoring Board overseeing Phase 3 trials of the Pfizer and Moderna vaccines has not identified or reported any serious safety concerns. All phase 3 studies have Data Safety and Monitoring Boards. The boards are made up of independent scientists hired by the company to look at the safety data and check at regular intervals whether the company should cancel or continue with the study. Additionally, two independent advisory committees will review a vaccine’s safety data before it is made available to the public. These committees are the Vaccines and Related Biological Products Advisory Committee (VRBPAC), which advises the FDA, and the Advisory Committee on Immunization Practices (ACIP), which advises the CDC. Learn more about the vaccine safety and development process.
You may experience mild to moderate side effects after receiving the vaccine. Side effects typically go away on their own after a few days. The most commonly reported side effects are:
The process of building immunity can cause symptoms. These symptoms are normal and show that your body’s immune system is responding to a vaccine. Other routine vaccines, like the flu vaccine, have similar side effects.
If you experience discomfort after the first dose of the vaccine, it is very important that you still receive the second dose a few weeks later for full protection.
The side effects after the second dose might be more intense or cause more discomfort than side effects after the first dose. In some cases, the side effects may be bad enough to interfere with your work and other normal daily activities for a day or two. Because the body has already responded to one dose of the vaccine, the second dose may cause a stronger immune response in your body. These side effects are expected and show that your body is continuing to build immunity.
If you are experiencing more intense side effects, stay well hydrated, rest, and consider over-the-counter medications like acetaminophen or ibuprofen (if they are normally safe for you to take). Side effects are proof that your body is building immunity in response to the vaccine and will typically go away on their own within a day or two.
For in-depth information about the side effects of the vaccines, see the CDC’s report on the Pfizer vaccine, Moderna vaccine and Johnson & Johnson vaccine.
A COVID-19 vaccine will give you protection against the disease without having to get sick with the actual virus. It is not possible to get COVID-19 from a vaccine, but it is possible to get symptoms that are consistent with COVID-19. The vaccine candidates use inactivated virus, parts of the virus (e.g., the spike protein), or a gene from the virus. None of these can cause COVID-19. The goal of the vaccine is to provide your body with the tools it needs to fight the COVID-19 virus if you were to get infected.
You will not be immediately protected from COVID-19 after receiving the vaccine. Studies show that it takes about 1-2 weeks after your last dose for your body to be able to protect itself against illness. While no vaccine is 100% effective, all available vaccines are shown to be highly effective at preventing moderate, severe and critical cases of COVID-19 illness, hospitalization and death. While there are several known variants of COVID-19, current evidence suggests the vaccine will protect against them.