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COVID-19 vaccines - what to expect

COVID-19 vaccines are used to prepare the body's immune system to protect against COVID-19. These vaccines are a vital tool to help stop the COVID-19 pandemic. Everyone age 12 and older should get the COVID-19 vaccination.

Learn what to expect before and after you are vaccinated for COVID-19.


Check with your state health department to find out when you are eligible to get a vaccine. You should be able to find out how to sign up for a vaccine and at what location. You can also check the CDC VaccineFinder to find out where to get a vaccine in your area.

Before you go to your appointment, check your confirmation emails to find out what you may need to bring to the appointment. For example, you may need your driver's license or other ID or proof of eligibility.

If you take any medicines, you should keep taking them as you usually do. If you take medicines that affect the immune system, talk with your health care provider to find out if getting the COVID-19 vaccine will work or cause any problems for you.

You should not take over-the-counter pain relievers such as aspirin, ibuprofen, or acetaminophen to help prevent side effects before you get the vaccine. It is not known if these medicines will affect how well the vaccine works. However, if you take these medicines regularly for other reasons, you can take them as you always do.

You should also not take antihistamines to help prevent an allergic reaction before you get the vaccine.

If you have any questions about your medicines, ask your health care provider or the vaccine provider.


You will need to wear a mask at the vaccination site the entire time. Everyone else at the site will also have to wear a mask. Try to stay at least 6 feet away from others at all times.

After you get your vaccine, you will wait at the vaccination site for 15 minutes to make sure you do not have a severe allergic reaction to the shot (this is very rare). If you have had a previous severe allergic reaction or if you have had an immediate reaction to immunizations in the past, you may need to wait for 30 minutes as a precaution. Vaccination sites are equipped to provide immediate care for severe allergic reactions and call for emergency medical care.

At your appointment, you will likely schedule the date of your second dose if you are receiving a 2-dose vaccine. You should receive a vaccination card that tells you what vaccine you received and the date and location you received it. Be sure to keep this card if needed for future use. You will need to bring it with you for your second dose if you are receiving a 2-dose vaccine.

You should contact the vaccination provider site:

  • If you did not get a vaccination card or you lose your card
  • If you did not schedule an appointment for a second dose
  • If you need to reschedule your second dose

You can also contact your state health department if you have questions about COVID-19 vaccinations.


If you got one of the 2-dose vaccines, you will need to receive your second dose within a specific number of weeks. You need to get the same type (brand) of vaccine for your second dose as you got for your first.

If you got the Pfizer-BioNTech COVID-19 vaccine, you should get your second Pfizer shot about 21 days (3 weeks) after the first shot.

If you got the Moderna COVID-19 vaccine, you should get your second Moderna shot about 28 days (4 weeks) after the first shot.

The day you get your first shot, you will likely also schedule the date for your second shot.

If you got the 1-dose vaccine, you only need one shot for this vaccine to protect you against COVID-19.

It takes time for your immune system to start protecting you after receiving the vaccine. You are considered fully vaccinated:

  • 2 weeks after your second shot of the Pfizer or Moderna vaccine
  • 2 weeks after your one shot of the J&J/Janssen vaccine

You are not fully vaccinated if it has been less than 2 weeks since your 1-dose shot or your second 2-dose shot. You are not fully vaccinated if you have only received 1 dose of a 2-dose vaccine.


Over time, COVID-19 vaccines appear to become less protective against the virus.

Giving a booster shot to people who have received 2 doses of either Pfizer or the Moderna mRNA vaccine likely provides more long-lasting immunity. As a result:

  • Booster shots are now recommended for people whose immune system is not strong enough (immunocompromised). This includes people receiving certain types of cancer treatment and people taking medicines that suppress the immune system. Ask your doctor if you are not sure.
  • A booster shot given 8 months after you received your second dose will also be offered to all people who have received these vaccines.

Boosters will also likely be needed for the J&J/Janssen vaccine, but it has not yet been decided when those may be available.

The CDC has recommendations for what it is safe to do once you are fully vaccinated.


While COVID-19 vaccines will not make you sick, they may cause certain side effects and flu-like symptoms. This is normal. These symptoms are a sign that your body is making antibodies against the virus.

Common side effects include:

  • Pain, redness, and swelling on the arm where you got the shot
  • Tiredness
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea

Some people get a red, itchy, swollen, painful rash in the arm where they got the shot. This is known as "COVID arm." This can occur days after getting the first shot. You should still get your second shot if you got a 2-dose vaccine. You can ask to have it in the other arm.

To help relieve side effects you should:

  • Move the arm where you got the shot often during the day
  • Apply a clean, cool washcloth to ease swelling and discomfort
  • Drink plenty of fluids
  • Dress lightly if you have a fever

Note that the side effects from the second dose may be more intense than those from the first shot. Symptoms from the shot may make you feel bad enough that you need to take time off from work or daily activities, but they should go away within a few days. Even if you do have side effects, it is still important to get the second shot. The risks of any side effects from the vaccine are far less dangerous than the potential for serious illness or death from COVID-19.

You may be instructed by the vaccine provider that you can take acetaminophen or another OTC medicine such as ibuprofen or aspirin to help relieve any vaccine side effects. Or, talk with your doctor about taking OTC medicine if you are not sure.

If symptoms do not go away in a few days, or if you have any concerns, you should contact your health care provider.

In rare cases, people have had severe and non-severe allergic reactions to the COVID-19 vaccines. If you have a severe or non-severe allergic reaction after getting the first shot of the COVID-19 vaccine, you should not get the second shot. Talk with your health care provider to see if there are other options.

When to Call the Doctor

Call your health care provider if you have any questions or concerns about COVID-19 vaccines.

If you think you are having a severe reaction to a COVID-19 vaccine after leaving the vaccination site, you should call 911 or the local emergency number right away. Symptoms of an immediate allergic reaction appearing in the first 4 hours after receiving the vaccine include:

  • Difficulty breathing, coughing, wheezing, or high-pitched breathing sounds
  • Swelling of the face, eyes, or tongue
  • Hives, itchiness, redness of the skin

Symptoms of severe reactions may also include:

  • Abdominal pain
  • Chest discomfort or tightness
  • Diarrhea
  • Difficulty swallowing
  • Dizziness or lightheadedness
  • Nausea or vomiting
  • Palpitations
  • Slurred speech
  • Unconsciousness

If you notice any unusual or concerning symptoms, seek medical care right away.

If you had an immediate allergic reaction to the first dose of a 2-dose vaccine, CDC recommends that you do not get the second dose of the same vaccine.


Centers for Disease Control and Prevention website. Getting your COVID-19 vaccine. www.cdc.gov/coronavirus/2019-ncov/vaccines/expect.html. Updated July 27, 2021. Accessed August 18, 2021.

Centers for Disease Control and Prevention website. Possible side effects after getting a COVID-19 vaccine. www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html. Updated August 16, 2021. Accessed August 18, 2021.

Centers for Disease Control and Prevention website. Preparing for your COVID-19 vaccination. www.cdc.gov/coronavirus/2019-ncov/vaccines/prepare-for-vaccination.html. Updated July 29, 2021. Accessed August 18, 2021.

Centers for Disease Control and Prevention website. What to do if you have an allergic reaction after getting a COVID-19 vaccine. www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/allergic-reaction.html. Updated March 4, 2021. Accessed August 18, 2021.

Review Date 5/14/2021

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 08/26/2021.