COVID-19 Resource Center

COVID-19 Vaccine Frequently Asked Questions

 Why should I get the COVID-19 vaccine?
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 and your family and friends.
 Does the COVID-19 vaccine protect against the Delta variant?
Currently, all COVID-19 vaccines authorized in the U.S. have proved to be highly effective against COVID-19, preventing severe disease, hospitalization, and death. Data show that the mRNA vaccines (Pfizer-BioNTech or Moderna) also provide protection against variants of the virus, including the Delta strain. Current data suggest lower vaccine effectiveness against infection and symptomatic disease caused by the variants; however, breakthrough infections in those fully vaccinated are associated with far fewer hospitalizations and deaths.
 Which vaccine should I take?
 The vaccines currently available in the U.S. include Pfizer-BioNTech, Moderna, and Johnson & Johnson/Janssen. Pfizer-BioNTech and Moderna are two-dose vaccines and Johnson & Johnson/Janssen is a one-dose vaccine. It is recommended that you take whichever vaccine is available to you as long as you do not have any contraindications. All U.S. COVID-19 vaccines have passed the same rigorous review process, and all are highly effective at preventing hospitalizations and deaths from COVID-19. You may wish to consider your specific circumstances if more than one vaccine choice is available. If you have concerns about your medical condition(s) and receiving the vaccine, consult with your doctor.
 For the two-dose vaccines, when do I get the second dose?
The timing between your first and second vaccine dose depends on which vaccine you received. You should have your second dose as close to the recommended 3-week or 1-month interval as possible. However, your second dose may be given up to 6 weeks (42 days) after the first dose, if necessary. You should not receive the second dose earlier than the recommended interval.
 Will I need a booster dose?
The CDC recommends a Pfizer-BioNTech booster dose 6 months after the second dose for some groups of people including:Adults age 65+ and those living in long-term care facilities should receive a booster dose,
  • Adults ages 50-64 with underlying medical conditions should receive a booster dose,
  • Adults ages 18-49 with underlying medical conditions may receive a booster dose based on an assessment of their individual benefits and risks, and
  • Adults ages 18-64 who are at increased risk for COVID-19 exposure and transmission because of occupational or institutional setting.
 Guidance is still forthcoming about booster doses for the Johnson & Johnson/Janssen and Moderna vaccines and the safety of mixing different vaccines.
 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 . There is also a possibility 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. 
 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—although rare—that you could be infected with the virus that causes COVID-19 again within 90 days. The vaccine is believed to provide protection with the benefit found in the clinical trials. However, you should not receive the vaccine while you are actively infected, but after full recovery (usually 14 days after symptom onset and clearance to end your isolation). Also, if you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting a COVID-19 vaccine.
 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 vaccine, including COVID-19 vaccines. See ACOG’s practice advisory and CDC recommendations on COVID vaccination for pregnant women.
 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). These are normal signs that your body is building protection. Side effects should only last a few days. It is important that you return for your second dose (if receiving the Pfizer-BioNTech or Moderna vaccine), even if the first dose caused mild side effects. Rarely, do more severe side effects occur.
 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 few or no side effects. For those who have side effects, they are usually mild, but may affect the ability to do some daily activities. If you experience a fever after vaccination, you may need to stay home from work pending further evaluation.
 Are there long-term side effects from the COVID-19 vaccine?
It will take more time and more people receiving the vaccine to learn about very rare or possible long-term side effects. However, at least 8-weeks of safety data were collected in the clinical trials for all the 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 U.S. Centers for Disease Control and Prevention (CDC) to monitor for safety issues across the country. Regarding the recent FDA approved Pfizer vaccine, more than half of the clinical trial participants were followed for safety outcomes for at least four months after the second dose. Overall, approximately 12,000 recipients have been followed for at least 6 months. The most reported side effects by those clinical trial participants who received Pfizer were pain, redness and swelling at the injection site, fatigue, headache, muscle or joint pain, chills, and fever.
 Should I take Tylenol or Motrin before my vaccine dose?
 No. Do not take medications before receiving the vaccine. Taking over-the-counter medications such as aspirin, acetaminophen (e.g., Tylenol) and ibuprofen (e.g., Motrin, Advil) before receiving a vaccine reduces the vaccine’s ability to work and can blunt your immune response to the vaccine.
 How much will it cost for me to get the vaccine?
Nothing – it’s free! The federal government is providing 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 this card because it may serve several important purposes in the future. It is recommended to take a picture or scan of the card and keep the original in a safe place.
 Will I be required to get vaccinated for work?
It depends. President Biden announced a plan that will mandate all employers with more than 100 workers to require vaccination or weekly testing for COVID-19. In addition, COVID-19 vaccines will be required for healthcare workers in facilities that receive Medicare and Medicaid funding, and for federal contractors and most federal employees. For these workers, weekly testing will no longer qualify 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 is 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 its benefits outweigh risks. Every study and every phase of every trial was carefully reviewed and approved by a safety board and the FDA, currently under Emergency Use Authorization (EUA). The process was transparent and rigorous, with continual oversight and expert approval.

On August 23, 2021, the FDA granted full approval to the Pfizer-BioNTech COVID-19 vaccine for individuals aged 16 years and older. For full approval of a new drug, the FDA requires extensive data on safety and effectiveness, inspection of manufacturing facilities, and a comprehensive review of all clinical and “real-world” use. This approval should provide additional confidence that the vaccine works and is 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.
 Will the COVID-19 vaccine alter my DNA?
No. COVID-19 mRNA or viral vector vaccines do not affect or interact with your DNA in any way. The mRNA from a COVID-19 vaccine never enters the nucleus of the cell, which is where our DNA is kept. After being used to produce the spike protein, your body gets rid of the mRNA within a few days. Likewise, the genetic material delivered by the viral vector does not integrate into your DNA.
 How long will vaccine immunity last?
Because this is a new virus with new vaccines to combat it, the length of immunity after developing COVID-19 or getting the vaccine is unknown. Experts are working to learn more about both natural immunity and vaccine-induced immunity.
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 infection, and even more effective against serious illness, hospitalizations, and deaths.
Do I still need to wear a mask after receiving the vaccine?
Fully vaccinated individuals may participate in many activities that they participated in prior to the pandemic but for some of these activities, they may have to resume masking based on state and local ordinances.

For additional questions, consult with your health care provider.

Last updated October 11, 2021.