What to Know After Receiving a COVID-19 Vaccine

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How do you know when you are fully vaccinated?

  • According to the Centers for Disease Control and Prevention (CDC), you are considered “fully vaccinated” after receiving all recommended doses in their primary series of COVID-19 vaccines:
    • weeks after you receive the second shot of a two-dose vaccine series 2 (such as the Pfizer or Moderna vaccine), or
    • weeks after you receive a shot of the single-dose Johnson & Johnson’s 2 Janssen vaccine.
  • Additionally, you are considered “up to date” with your COVID-19 vaccines once you receive all recommended vaccines, including any booster dose(s) when eligible.
  • It typically takes this amount of time for the body to build protection, or immunity in the form of antibodies, against the virus that causes COVID-19.
  • Researchers continue to study and learn more about how long each vaccine will protect against COVID-19.

Sources: CDC – Stay Up to Date with Your Vaccines (Updated 1/16/22) | CDC – Key Things to Know About COVID-19 Vaccines (Updated 1/12/22)

Can I still get COVID-19 if I’ve been vaccinated?

COVID-19 vaccines protect everyone ages 5 years and older from getting infected and severely ill, and significantly ࡟ reduce the likelihood of hospitalization and death. As variants like Delta and Omicron continue to emerge, vaccinated individuals may still get infected with the virus. These “breakthrough infections” – which happen when fully vaccinated individuals are infected with the virus – are generally less severe compared to infections experienced by the unvaccinated. However, individuals who get breakthrough infections can be contagious, so it is important to follow the CDC’s updated quarantine and isolation guidelines.

Source: CDC – Vaccine Breakthrough Infections (Updated 12/17/21)

Does the vaccine impact COVID-19 test results?

No, none of the vaccines currently authorized for use in the United States can cause you to test positive on viral COVID tests, which are used to see if you have a current infection. There is a possibility that you could test positive on a COVID-19 antibody test – if your body develops antibodies and an immune response – which is the goal of vaccination, and/or could mean that you had a previous infection.

Source: CDC – Myths and Facts about COVID-19 Vaccines (Updated 12/15/21)


How long will the vaccine last?

  • COVID-19 vaccines remain highly effective in preventing serious illness caused by the COVID-19 virus, but protection can wane over time, particularly with the emergence of variants like Omicron and Delta.
  • Booster shots increase the level of immune response in those who are fully vaccinated and provide more protection against COVID-19. Researchers will continue to study and learn more about how long vaccines protect against COVID-19 and the effectiveness of each vaccine against variants. In the meantime, even after receiving all recommended doses in your primary series of COVID-19 vaccine, you should get booster shots when eligible and you can also take precautions to protect yourself and others, like wearing a well-fitted mask and practicing physical distancing in public.

Sources: Phase 3 Clinical Trial Data – Pfizer/BioNTech; CDC – Morbidity and Mortality Weekly Report (Updated 4/2/21) | CDC – COVID-19 Vaccine Booster Shots (1/19/22)


What side effects can I expect after receiving a COVID-19 vaccine?

  • The most common side effect of the vaccines is mild injection site pain, including redness or swelling, but you might also experience fatigue, fever, headache, muscle pain, chills, or nausea. All of these are normal signs that your body is building antibodies as protection against the virus and usually go away within a day or two.
  • If you are receiving one of the two-shot vaccines, the side effects after the second shot may be more intense than what you experienced with the first. This is because your immune cells are programmed to respond faster and more forcefully when they encounter an invader for a second time – this is true whether you are experiencing a natural infection or antigens from a vaccine. It is a normal sign that your body is building up protection against the virus.
  • ,It is important to note that many people have no side effects at all but a lack of side effects does not mean the vaccine isn’t working.

Sources: CDC – Possible Side Effects After Getting a COVID-19 Vaccine (Updated 1/12/22)

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What can I do to treat possible side effects from the vaccines? Is there anything I should, or should not, do?

  • To reduce any pain or discomfort at the injection site, apply a cool, damp cloth over the area and move or exercise your arm.
  • You can take over-the-counter medications such as ibuprofen, acetaminophen, aspirin, or antihistamines as needed for side effects, but these medicines are not recommended before receiving your vaccine.
  • If you have other medical conditions, talk to your doctor before taking medications to treat any side affects you may experience from the vaccine.

Sources: CDC – Possible Side Effects After Getting a COVID-19 Vaccine (Updated 1/12/22)


Can I take other vaccines (flu shot, pneumococcal vaccine, etc.) at the same time as a COVID-19 vaccine?

  • Yes, COVID-19 vaccines and other vaccines can be co-administered without regard to timing. In other words, an individual can be given a COVID-19 vaccine and another vaccine (for example, flu, tetanus, measles) on the same day, as well as within 14 days of each other.

Sources: CDC Pandemic Guidance, updated 4/6/21

If I have been vaccinated and later develop COVID-19 symptoms, do I still need to get tested?

  • Yes, any vaccinated person who experiences symptoms consistent with COVID-19 should isolate themselves from others, be clinically evaluated for COVID-19, and tested. If you test positive or have symptoms, regardless of vaccination status, stay home for 5 days and isolate from others in your home.

Sources: CDC – Stay Up to Date with Your Vaccines (Updated 1/16/22) | CDC – Quarantine and Isolation (Updated 1/20/22)

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