COVID-19 Resource Center

COVID-19 Vaccine Frequently Asked Questions

 Why should I get the COVID-19 vaccine?
For the vast majority of people, the benefits of preventing a COVID-19 infection outweigh any risks of the vaccine. The vaccine helps protect you from getting COVID-19 and is considered a safe way to build protection against the disease. COVID-19 can have serious, life-threatening complications, and there is no way to know how COVID-19 will affect you or your loved ones. If you still get infected, the vaccine may prevent serious illness and death. By getting vaccinated, you are helping to protect yourself, your family and friends.
 Does the COVID-19 vaccine protect against the Omicron variants?
Currently, all COVID-19 vaccines authorized in the U.S. have proved to be highly effective against preventing severe disease, hospitalization, and death from COVID-19. Data show that the mRNA vaccines (Pfizer-BioNTech or Moderna) also provide protection against variants of the virus, including the Omicron strains. While there is lower vaccine effectiveness against infection and symptomatic disease caused by the Omicron variants, the breakthrough infections occurring in those with up-to-date vaccination are associated with fewer hospitalizations and deaths.
 Which vaccine should I take?
The vaccines currently available in the U.S. include Pfizer-BioNTech, Moderna, Johnson & Johnson/Janssen, and Novavax. All U.S. COVID-19 vaccines have passed the same rigorous review process, and all are highly effective in preventing hospitalizations and deaths from COVID-19. Generally, mRNA vaccines are recommended as a first option due to their excellent safety profiles and effectiveness. The Johnson & Johnson/Janssen vaccine should be reserved for individuals who are unable to take an mRNA vaccine due to medical contraindications or local supply constraints. If you have concerns about your medical condition(s) and receiving the vaccine, consult with your physician.
 For the two-dose primary vaccines, when do I get the second dose?

The timing between your initial and second vaccine dose depends on which vaccine you received. If you received either Pfizer-BioNTech or Moderna, you should have received your second dose near the recommended 3-week or 1-month interval when possible. If for some reason you did not get the second dose at 3-4 weeks after the first, then it is recommended that you get the second dose at the earliest opportunity to do so. You should not receive the second dose earlier than the recommended interval. The second dose of an mRNA vaccine may be given at no less than 3 weeks (for Pfizer-BioNTech) or 4 weeks (Moderna). An 8-week interval may be optimal for some people ages 12 years and older, especially for males ages 12 to 39 years. The Novavax vaccine is a newer two-dose vaccine given 3-8 weeks apart. This information does not apply to the Johnson & Johnson/Janssen vaccine. See below for additional information on booster dose(s).

 Will I need a booster dose?

Vaccine recommendations are based on your age, the vaccine you first received, and the time since last dose. Individuals 18 years of age and older are eligible for the Moderna updated bivalent (Omicron) booster dose if it has been at least 2 months since they have completed primary vaccinations, or have received the most recent booster dose with any authorized or approved COVID-19 vaccine. Individuals 12 years of age and older are eligible for Pfizer-BioNTech updated bivalent (Omicron) booster dose if it has been at least 2 months since they have completed primary vaccination, or have received the most recent booster dose with any authorized or approved COVID-19 vaccine. Eligible individuals may choose which vaccine they receive as a booster dose. CDC allows for a booster dose that is not the same type as the initial vaccination(s). Novavax was only approved as a primary vaccine, not as a booster, at least so far.  

Is the updated bivalent (Omicron) booster safe?
The same technology was used for the bivalent (Omicron) booster as the primary vaccine series, which has shown a good safety profile. The updated bivalent (Omicron) booster is similar to the influenza vaccine covering multiple strains of the virus. 
 In those who are vaccinated with two-doses and have a breakthrough infection, what is the timing of receiving the bivalent (Omicron) booster?

For anyone who has been infected with COVID-19, their next dose may be delayed up to 3 months from when symptoms started or, if they did not have symptoms, when they received a positive test. This possible delay can happen with a primary dose or a booster dose. Consult your physician if you have any questions about the timing of your primary or booster dose.

 Can the vaccine give me COVID-19?  
No. None of the COVID-19 vaccines authorized for use in the U.S. contain the live virus that causes COVID-19.
 Will I test positive once I get the COVID-19 vaccine?
No. Viral tests such as PCR used to diagnose COVID-19 check samples from the respiratory system for the presence of the virus that causes COVID-19. Since the vaccines do not contain the live virus, they will not affect your PCR test result. However, it typically takes a few weeks for the body to build immunity after vaccination. Therefore, it is possible to test positive if you were infected with the virus that causes COVID-19 just before or just after vaccination.

It is possible you may test positive on some antibody tests if your body develops an immune response. Positive antibody tests can indicate you had a previous infection or vaccination and that you may have some level of protection against the virus. Antibody (Ab) testing is used in highly specialized situations (e.g., studies and surveillance) and should not be utilized to inform vaccination for employees. 
 Should I get vaccinated if I already had COVID-19?
Yes. Experts do not yet know how long you are protected from getting sick again after recovering from COVID-19. Even if you have already recovered from COVID-19, it is possible that you could be infected with the virus that causes COVID-19 again. Receiving the vaccine when you have already had COVID-19 significantly enhances your immune protection and further reduces your risk of reinfection. For anyone who has been infected with COVID-19, their next dose may be delayed up to 3 months from when symptoms started or, if they did not have symptoms, when they received a positive test. This possible delay can happen with a primary dose or a booster dose. Consult your physician if you have any questions about the time of your primary or booster dose. 
 If I am pregnant, can I get the COVID-19 vaccine?
Yes. There is currently no evidence that antibodies formed from COVID-19 vaccination cause any problem with pregnancy, including the development of the placenta. Also, people who are trying to become pregnant now or who plan to try in the future may receive the COVID-19 vaccine. There is no evidence that fertility problems are a side effect of any of the COVID-19 vaccines. See ACOG’s practice advisory and CDC's recommendations on COVID vaccination for pregnant women. CDC has also established the v-safe COVID-19 Vaccine Pregnancy Registry to learn more about this issue.
 Are there any side effects from the COVID-19 vaccine?
 Yes. As with many vaccines, there may be mild side effects (pain/swelling in the arm where you received the shot, fever, chills, fatigue, and headache). Side effects should only last a few days. It is important that you return for your second dose (if receiving the Pfizer-BioNTech, Moderna, or Novavax vaccine), even if the first dose caused mild side effects. Rarely, do more severe side effects occur. Use your smartphone to tell CDC how you, or your dependent, feel after getting any dose of the COVID-19 vaccine. Your participation in v-safe helps them monitor the safety of COVID-19 vaccines for everyone. There are rare side effects that have occurred, but at the current time, there are no common, severe side effects that have been reported despite millions of vaccine administrations.
 If I have side effects from COVID-19 vaccination, can I return to my workplace?
You should be able to return to your workplace after receiving the vaccine. Most people who get the vaccine have mild or no side effects. For those who have side effects, they may uncommonly affect your ability to do some daily activities. If you experience a fever after vaccination, you may need to stay home from work and may need further evaluation.
 Are there long-term side effects from the COVID-19 vaccine?
It will take more time to learn about very rare or possible long-term side effects. However, safety data have been collected for many months for all authorized vaccines. It is unusual for vaccine side effects to appear more than 8 weeks after vaccination. Vaccines do not generally have long-term side effects and there is no reason to believe the COVID-19 vaccine will be an exception. Systems are in place at the CDC to monitor for safety issues across the country. 
 Should I take Tylenol or Motrin before my vaccine dose?
 Talk to a doctor about taking over-the-counter medicine, such as ibuprofen, acetaminophen, aspirin (only for people ages 18 years or older), or antihistamines for any pain and discomfort experienced after getting vaccinated.
 How much will it cost for me to get the vaccine?
The Federal government provides the vaccine free of charge to ALL people living in the U.S. whether or not they are citizens. Providers can be reimbursed for vaccine administration by the patient’s public or private insurance company or, for uninsured patients, by the Health Resources and Services Administration’s Provider Relief Fund. No one can be denied a vaccine if they are unable to pay the vaccine administration fee.
 Will I receive documentation of my vaccine/a vaccine card?
When you receive your COVID-19 vaccination, you will be given a vaccine card as documentation. The card will contain your name and birthdate, vaccine manufacturer and lot number, as well as, where the vaccine was administered and the date the vaccine was given to you. It is important to hold onto your COVID-19 vaccination card because it may serve several important purposes in the future. It is recommended to take a cell phone picture of it. If you do not take a cell phone photo of it, it is recommended you scan the card. Consider making at least one photocopy of the card. Be sure to keep the original in a safe place. Also, COVID vaccine apps are becoming increasingly available and are being used for vaccine vaccine verification often at the state level (e.g.,  
 Will I be required to get vaccinated for work?
It depends. COVID-19 vaccines are currently required for healthcare workers in facilities that receive Medicare and Medicaid funding. For those workers, weekly testing no longer qualifies as a substitute for vaccination. Check with your employer to see if they have any rules that apply to you.
 Is the vaccine safe since it was developed so quickly?
Yes. The U.S. Food and Drug Administration (FDA) approves a vaccine for use only if there are enough data to suggest that it is safe and effective; this is after clinical trials have been conducted with thousands of people of various ages, races, and ethnicities and when the benefits outweigh risks. Every study and every phase of every trial was carefully reviewed and approved by a safety board and the FDA. The process was transparent and rigorous, with continual oversight and expert approval.

The FDA granted full approval for the Pfizer-BioNTech COVID-19 vaccine for individuals aged 16 years and older (8/23/21) and full approval for the Moderna COVID-19 vaccine for individuals aged 18 years and older (1/31/22). For full approval of a new drug or vaccine, the FDA requires extensive data on safety and effectiveness, inspection of manufacturing facilities, and a comprehensive review of all clinical and “real-world” use. These approvals should provide additional confidence that the vaccines work and are safe.

The FDA will continue to monitor and oversee vaccine production to ensure all safety protocols are followed. The FDA and CDC also collect and analyze information from reports of any side effects that may occur after a vaccine has been licensed. CDC developed a smartphone-based tool, v-safe, to identify any safety issues with COVID-19 vaccines. Register to use v-safe after you are vaccinated.
 How long will vaccine immunity last?
Because this is a relatively new virus with recent vaccines to combat it, the length of immunity after developing COVID-19 or getting the vaccine is unknown. Studies are ongoing and experts are working to learn more about both natural immunity and vaccine-induced immunity. Research shows that FDA-authorized or approved vaccines are effective at reducing the risk of severe COVID-19 disease. Getting COVID-19 also provides infection-induced immunity. The length of protection is unclear for either vaccination or infection-induced immunity, although there is consistent evidence suggesting that immunity may decline with time. Protection may be the greatest from 2-6 weeks after vaccination. After 2-3 months, protection against infection wanes significantly. However, protection against severe disease lasts much longer. The CDC has recommendations for booster doses. Refer to earlier sections to see which booster dose is correct for you.
If the vaccine is effective, why are there reports of infections
and death among those vaccinated?
No vaccine is 100% effective against preventing infection. But, we do know that the COVID-19 vaccine is highly effective against serious illness, hospitalizations, and deaths. Severe outcomes and deaths are increasingly only being experienced in either the unvaccinated and/or severely immunocompromised individuals.
Do I still need to wear a mask after receiving the vaccine?
Individuals with up-to-date vaccination may voluntarily participate in activities that they participated in prior to the pandemic, but for some of these activities, masking may be required based on employer/institutions policies or state and local ordinances. 

For additional questions, consult with your health care provider.

Last updated September 29, 2022.