COVID-19 Vaccine FAQs

Updated February 12, 2021

Key Definitions

What is herd immunity? What is the goal for people living in the US  with respect to the COVID-19 vaccine?

Herd immunity is a term used to describe the situation when enough people have protection—from either previous infection or vaccination—that it is unlikely a virus or bacteria can spread and cause disease. As a result, everyone within the community is protected even if some people have not been previously infected or had a vaccination themselves. The percentage of people who need to have protection in order to achieve herd immunity varies by disease. (Source)

Experts do not know what percentage of people need to be vaccinated to achieve herd immunity to COVID-19. (Note: Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases and chief medical adviser on COVID-19 to President Biden, has estimated this percentage to be 70%-85%.)     

What does “emergency use authorization” mean?

The FDA may issue an emergency use authorization (EUA) that allows for the distribution of an unapproved medication or medical product during public health emergencies; this could include vaccines for COVID-19.

What is the difference between efficacy and effectiveness ?

Efficacy refers to a result acquired under ideal or controlled conditions. Vaccine efficacy is defined as how well a vaccine performs under the best of conditions, such as randomized controlled clinical trials. Effectiveness refers to a result acquired in an average clinical or real-world environment

What is an mRNA vaccine?

mRNA vaccines for COVID-19 work differently than traditional vaccines because they DO NOT put a weakened or inactivated live virus into our bodies. Instead, they use material from the virus that gives our cells instructions for how to make a protein that triggers an immune response. This immune response protects us from getting infected should the real, live virus that causes COVID-19 enter our bodies.

COVID 19 Vaccine Research: Effectiveness and Inclusion

Currently, two COVID-19 vaccines are approved for use in the United States – the Pfizer vaccine and the Moderna vaccine. Is one better than the other?

As of now, the two vaccines seem to work equally well. The main difference is the temperature of the cold-storage requirement.

What is the difference between the vaccines currently available in the US?

There are two FDA-approved COVID-19 mRNA vaccines:

  • Pfizer-BioNTech COVID-19 vaccine, recommended for people aged 16 years and older (two shots given 21 days apart) in the muscle of the upper arm; does not contain eggs, preservatives, or latex
  • Moderna COVID-19 vaccine, recommended for people aged 18 years and older (two shots, 28 days apart) in the muscle of the upper arm; does not contain eggs, preservatives, or latex. (Source)

If you want more details about the differences, you can refer to our update posted on January 11, 2021.

Should I get the COVID-19 vaccine if I have already tested positive for the COVID-19 virus?

Experts recommend people get vaccinated even if they have had COVID-19. People who get COVID-19 do develop antibodies that provide some protection against getting infected again. However, it is not known exactly how long antibodies last after a person recovers.

How did COVID 19 vaccines get developed so quickly when vaccines usually take years to develop? 

Several agencies within the federal government coordinated an effort to accelerate vaccine development by pharmaceutical companies to allow clinical trials to proceed more quickly than in the past. The technology underlying development of the Pfizer and Moderna RNA vaccines existed prior to COVID19 and was rapidly deployed to help fight the pandemic. The U.S. Food and Drug Administration (FDA) will not and has not approved a vaccine unless there are data to show that the vaccine is safe for use following a series of randomized, placebo-controlled clinical trials in thousands of people as well as effective at preventing the disease and proven to be produced or manufactured consistently, safely, and at a high quality.

Why are two shots of the vaccine needed?

You need two shots of the vaccine because the first shot helps the immune system create a response against SARS-CoV-2, the virus that causes COVID-19, while the second shot further boosts the immune response to ensure long-lasting protection.

Will the vaccine interfere with my cancer treatment?

As of now, we do not have any reason to believe that the vaccines may interfere with cancer treatment. If a patient is in active treatment and is receiving chemotherapy or radiation therapy, it is advisable to discuss COVID-19 vaccination with their doctor. This is because an active immune system is needed for the vaccine to work. Chemotherapy or radiation therapy can dampen the immune response and make the vaccine less effective.

Were there racial and ethnic minority populations included in the vaccine trials?

In clinical trials for the Pfizer/ BioNTech and Moderna vaccine, 10% of U.S. participants for both vaccines were Black, even though 13% of the U.S. population is Black.  Thirteen and twenty percent of subjects, respectively, were Hispanic, under the nearly 19% of the population that is Latino. Asian and American Indian participation was roughly in line with their shares of the country’s population. (Source)

Safety and Administration

Who should receive the COVID-19 vaccine?

We recommend the COVID-19 vaccine for virtually all lung cancer patients, with the exception of those with a known severe reaction to polyethylene glycol or polysorbate. Medical and professional societies, such as American Association for Cancer Research, American Society of Clinical Oncology, American Cancer Society, Society for Immunotherapy of Cancer, and European Society for Medical Oncology, recommend that cancer patients receive the COVID-19 vaccine. Also, the COVID-Lung Cancer Consortium (CLCC) strongly recommends that lung cancer needs to be prioritized for vaccination. The ultimate decision may also be influenced by the patient’s health status as well as type and timing of their cancer treatment.

How can you receive the COVID-19 vaccine?

Patients and their caregivers should speak with their cancer physician or primary care provider about how to receive the vaccine.

Is the vaccine safe?

Both vaccines are considered to be safe. People who have had a history of developing severe allergic reactions to other vaccines or medicines for any reason or who are known to have a history of anaphylaxis (a severe, potentially life-threatening allergic reaction) should discuss whether to get the vaccine with their physician.

Can I get COVID-19 from a COVID-19 vaccine?

NO, the vaccine does not contain the virus, SARS-CoV-2, and cannot give you COVID-19. (Source)

As explained above under "What is an mRNA vaccine":

mRNA vaccines for COVID-19 work differently than traditional vaccines because they DO NOT put a weakened or inactivated live virus into our bodies. Instead, they use material from the virus that gives our cells instructions for how to make a protein that triggers an immune response. This immune response protects us from getting infected should the real, live virus that causes COVID-19 enter our bodies.

How am I monitored after I receive a COVID-19 vaccine?

All people who get a COVID-19 vaccine should be monitored on site. People who have had severe allergic reactions or who have had any type of immediate allergic reaction to a vaccine or injectable therapy should be monitored for at least 30 minutes after getting the vaccine. All other people should be monitored for at least 15 minutes after getting the vaccine.

If I am allergic to eggs, should I avoid these vaccines?

 The Pfizer and Moderna mRNA vaccines do not contain eggs.

Do I have to receive both doses of a COVID-19 vaccine to prevent COVID-19?


Do both doses need to be of the same brand? How do I keep track?

Yes, the second dose needs to be the same vaccine brand as the first dose. People are given a vaccine certificate stating the brand at the time of the first dose.

Also, the vaccination provider may include your vaccination information in your state/local jurisdiction’s Immunization Information System (IIS) or other designated system. This will ensure that you receive the same vaccine when you return for the second dose. (Sources 1 and 2)

May I get a COVID-19 vaccine, the flu vaccine, and/or the Zoster vaccine at the same time?

Given the lack of data on the safety and effectiveness of mRNA COVID-19 vaccines administered simultaneously with other vaccines, the vaccine series should routinely be administered alone, with a minimum interval of 14 days before or after administration with any other vaccine. (Source)

Will a COVID-19 vaccination hurt? How can I avoid a sore arm?

Some people may have muscle soreness at the injection site. The best position to keep your arm in during the injection is relaxed with your elbow at your side.

What may be some common side effects of a COVID-19 vaccine?

People may have pain, redness, and/or swelling on the arm where they got the injection. People may experience fever, chills, tiredness, headache, and body aches.[A4]  While these side effects are more common after the second dose, they may also occur after the first dose. (Source)

What do I do if I get a side effect that I believe is from a COVID-19 vaccine?

People should contact their primary care physician or oncologist if the redness or pain at the injection site increases after 24 hours or if other side effects are worrying and do not seem to be going away after a few days. (Source)

  • Side effects may feel like the flu, but they should go away in a few days.
  • If people are having a severe allergic reaction after leaving the vaccination site, they should seek immediate medical care by calling 911.

Children,  Pregnancy and Lactation (Breastfeeding)

May my children get a COVID-19 vaccine?

Not yet. These vaccines were not tested among children. It is recommended that those 16 years and older may get the Pfizer vaccine, while those 18 years and older may get the Moderna vaccine.

May I get a COVID-19 vaccine if I am pregnant?

The actual risks of mRNA vaccines to the pregnant person and her fetus are unknown because these vaccines have not been studied in pregnant women. Pregnant women are at increased risk for severe illness from COVID-19 and might be at increased risk of adverse pregnancy outcomes such as preterm birth. The CDC and the independent Advisory Committee on Immunization Practices (ACIP) have provided information to assist pregnant people with their decision to receive a COVID-19 vaccine. (Source)

May I get a COVID-19 vaccine if I am breastfeeding?

There are no data on the safety of COVID-19 vaccines in lactating women or on the effects of mRNA vaccines on the breastfed infant.


Can a COVID-19 vaccine change my genetic information?

No. COVID-19 vaccines do not affect or interact with our DNA in any way. mRNA never enters the nucleus of the cell, which is where our DNA (genetic material) is kept. The cell breaks down and gets rid of the mRNA soon after it is finished using the instructions. (Source)

Do COVID-19 vaccines contain microchips?

No. After receiving the vaccination, people will receive a hard copy with their vaccine dose/type written on the certificate or a “digital” form of the certificate that allows you to receive an electronic copy that you can print from home. (Note: Conservative media took a comment from Bill Gates out of context when he referred to the “digital" certificates.)


Should caregivers receive the COVID-19 vaccine?

If your caregiver(s) is/are eligible to receive the vaccine, we strongly recommend they receive the COVID-19 vaccine.

Will the vaccine provide complete protection?

Currently, the science shows that the vaccines are highly effective in preventing people from getting seriously ill from COVID-19, but no vaccine is 100% effective. To ensure complete protection, continued safety measures, such as wearing a mask, social distancing, and washing your hands often, are strongly recommended.

What is not yet known about the protection of COVID-19 vaccination?

Experts need to understand more about the protection that COVID-19 vaccines provide in real-world conditions. They don’t yet know if the vaccine will prevent you from spreading the virus to other people even if you can’t get sick yourself. Therefore, it is imperative that you maintain the protective measures such as wearing a face mask, socially distancing (particularly indoors) and washing your hands frequently.