Updated on May 6, 2021
As the COVID-19 vaccines are introduced, many people have questions about development, safety, access, cost, and other common concerns. This page provides information about what scientists do and do not know yet about the vaccines, drawing from the World Health Organization, the United States Centers for Disease Control and Prevention, and other trusted sources. Some of this language is used word for word, and other language is paraphrased. We would like to acknowledge the hard work of these organizations in compiling this information.
Getting vaccinated is one of many steps you can take to protect yourself and others from COVID-19. Other recommendations including the use of face masks, distancing and washing hands should continue to be followed to reduce your chance of being exposed to the virus or spreading it to others.
If you cannot find the information you are looking for on this page, you are invited to submit your own questions and our team will look into the answers.
How does the COVID-19 vaccine work?
There are currently multiple COVID-19 vaccines being developed, tested and approved. They are all meant to teach the body’s immune system to safely recognize and block the coronavirus. The various types include:
- mRNA vaccines, which contain synthetic mRNA, which is information used to make a coronavirus spike protein. This protein alone cannot cause COVID-19. Our cell uses this mRNA to make the viral protein which then causes our immune system to make antibodies to fight the virus when it is encountered.
- Viral vector vaccines, which use a genetically engineered virus to carry the genetic code (such as DNA) to generate a protein that prompts an immune response, without causing COVID-19.
- Inactivated or weakened virus vaccines, which use a form of the virus that has been inactivated or weakened so it doesn’t cause disease, but still generates an immune response.
- Protein-based vaccines, which use harmless fragments of proteins or protein shells that mimic the COVID-19 virus to generate an immune response, without causing COVID-19.
For more information: https://www.who.int/news-room/feature-stories/detail/how-do-vaccines-work
What are mRNA vaccines and how do they work?
Messenger RNA vaccines—also called mRNA vaccines—are some of the first COVID-19 vaccines (Moderna and Pfizer-BioNTech) authorized for use in the United States. mRNA vaccines are a new type of vaccine to protect against infectious diseases.
The immune system helps the body fight infections. To trigger a protective response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines. Instead, they teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. The antibodies produced as a result are helpful to detect and launch an attack against the real viruses.
Why was the COVID-19 vaccine developed so much faster than other vaccines?
The vaccine development process is happening faster because vaccine research and development, clinical trials, manufacturing, and plans for distribution are taking place at the same time. This method removes delays that occur when these processes are carried out one after the other. Operation Warp Speed also accelerated the development by investing in and coordinating the various steps. Steps to ensure safety are not being eliminated.
How are vaccines tested?
Possible vaccines go through an intensive testing process. Testing includes careful examination of the vaccine and its ingredients. These tests evaluate the safety of the vaccine and how well it prevents a disease. Tests are first done in research labs, and then if the vaccine looks effective and safe, researchers can apply to do clinical trials. Clinical trials typically involve several thousand healthy volunteer participants in three phases with increasing numbers of participants in each phase. Trials in all phases have to follow strict safety regulations that are set by national regulatory authorities that prioritize participant safety. When vaccine manufacturers apply for approval for their vaccine, the results of all the clinical trials are considered.
How do we know the vaccine is safe?
The most commonly used vaccines we have today have been in use for decades, with millions of people receiving them safely every year. As with all these successful vaccines, COVID-19 vaccines have also undergone extensive and rigorous testing before being approved. Scientists around the world have been working since early 2020 to develop the current possible COVID-19 vaccines and go through all of the testing processes to ensure they are safe. The vaccine safety is also monitored after the vaccines have been introduced which is called post-market surveillance. This ensures that the vaccines will continue to meet the same quality, safety and performance requirements as when they were initially introduced in the market.
Are there side effects to receiving the vaccine?
COVID-19 vaccination will help protect you from getting COVID-19. You may have some side effects, which are normal signs that your body is building protection. Common side effects include pain and swelling at the site of injection, and flu-like symptoms such as fever, chills, tiredness and headache. These should go away in a few days.
It has been seen that some people can develop allergic reactions after getting the COVID-19 vaccine. If you have ever had a severe allergic reactions to other vaccines or injectables, it is recommended that you speak to your doctor before getting vaccinated.
Is it safe for me to get the vaccine if I have a health condition such as diabetes, high cholesterol, obesity, or heart disease?
Currently approved COVID-19 vaccines may be administered to people with underlying medical conditions if they have not had severe allergic reactions to other vaccines or injectables.
People with a weakened immune system due to other illnesses or medication, may receive the COVID-19 vaccine. However, they should be aware of the limited safety data on the mRNA COVID-19 vaccines. If you have additional questions about whether it is safe for you to get the COVID-19 vaccine, talk with your healthcare provider.
Is it safe for me to get the vaccine if I am pregnant or breastfeeding?
Pregnant people are at an increased risk for severe illness from COVID-19 when compared with non-pregnant people. Pregnant people with COVID-19 might also be at increased risk of adverse pregnancy outcomes, such as preterm birth, compared with pregnant women without COVID-19.
Based on how these vaccines work, experts believe they are unlikely to pose a risk for people who are pregnant. However, currently there is limited data on the safety of getting vaccinated against COVID-19 among people who are pregnant and breastfeeding, though scientists are planning to study this further. The CDC recommends talking with your healthcare provider about the vaccine if you are pregnant or breastfeeding.
For more information, please visit: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html
Vaccine Access and Cost
Will I have to pay for the vaccine? What if I do not have health insurance?
Vaccines will be provided at no cost. However, providers can charge an administration fee. This fee can be covered by public or private insurance or by the Health Resources and Serviced Administration’s Provider Relief Fund, for those who are uninsured.
If you receive a bill for your COVID-19 vaccine, know that you should not have to pay it. Call your insurance company or, if you do not have insurance, call the location where you received your vaccine and let them know that they cannot charge you for the vaccine.
Will there be enough vaccine for everyone?
Everyone ages 16 and older is now eligible to receive the COVID-19 vaccine in the United States. It is important to get a vaccine as soon as possible to help stop the spread of the COVID-19 pandemic.
To find a vaccine in the United States, visit: https://www.cdc.gov/vaccines/covid-19/reporting/vaccinefinder/about.html
Even after receiving the vaccine, it is important to continue to follow the general recommendations including the use of face masks, distancing, and washing hands.
What are the vaccines available to me?
|Manufacturer||Efficacy||Effectivity against COVID-19 variants||Dosing (number and interval)||Approval date|
|Pfizer||95% efficacy in preventing COVID-19
100% effective at preventing severe disease
|Found to be protective against the variant that was first detected in Great Britain (B.1.1.7), but it may be less effective against the variant first detected in South Africa (B.1.351)||Two shots, 21 days apart||December 11, 2020|
|Moderna||94.1% effective at preventing symptomatic infection
(the efficacy rate drops to 86.4% for people ages 65 and older)
|May provide protection against the B.1.1.7 and B.1.351 variants.||Two shots, 28 days apart||December 18, 2020|
|J&J||72% overall efficacy and 86% efficacy against severe disease in the U.S.||Offers protection against the B.1.1.7 variant. 64% overall efficacy and 82% efficacy against severe disease in South Africa, where the B.1.351 variant was first detected||Single shot||February 27, 2021|
Updated Are all of the vaccines the same? Will I have a choice between them?
The Pfizer and Moderna vaccines are both about 95% effective. The Pfizer vaccine needs to be kept at extremely cold temperatures, while the Moderna vaccine can be kept in a normal freezer. The two doses of the Pfizer vaccine are given 21 days apart and the vaccine is authorized for people ages 16 and up. The two doses of the Moderna vaccine are given 28 days apart and the vaccine is authorized for people ages 18 and up.
The Johnson & Johnson Janssen (J&J/Janssen) vaccine requires only one dose. It was about 66.3% effective at preventing COVID-19 infection in clinical trials (efficacy). It is highly effective at preventing hospitalization and death among those who did become infected with COVID-19. It is authorized for use in people ages 18 and up, however, women younger than 50 years old especially should be aware of the rare risk of blood clots with low platelets after vaccination, and that other COVID-19 vaccines are available where this risk has not been seen.
Whether you will have a choice of vaccine depends on a number of factors, including the supply in your area at the time you’re vaccinated and whether certain vaccines are found to be more effective in certain populations, such as older adults.
New Can I mix and match vaccines?
After your first dose, you’ll receive a vaccination card indicating which vaccine you were given and the recommended date of the second dose. You’ll also receive an information sheet telling you more about the vaccine. To avoid delays, set up your second appointment at the same location where you got the first shot. That way you’ll know you’ll get the same vaccine. In most cases, health workers will not give you a different second dose than the one indicated on your vaccination card. If you start with the Pfizer vaccine, you should get the second dose of the Pfizer vaccine three weeks later. If you start with the Moderna vaccine, you should get the Moderna vaccine four weeks later.
If you receive the J&J vaccine, you do not need a second shot.
Why do some people get one shot and some get two doses?
In cases of Pfizer/ Moderna vaccines, the first dose helps the body recognize the virus and gets the immune system ready to protect from future infection, while the second dose strengthens that immune response. This makes the body prepared to fight infection.
Johnson & Johnson’s (J&J/Janssen) vaccine is a single dose vaccine and uses a different kind of technology than the previously authorized Pfizer and Moderna. The trials for J&J/Janssen demonstrated that it was 66.3% effective at preventing COVID-19 infection, with a single dose.
Can I get COVID-19 from the vaccine?
No, the different types of vaccines have different materials in them that will signal our bodies to produce the proteins or antibodies to protect us from the virus. NONE of these vaccines contain the active COVID-19 virus.
The immune response that is initiated in the body might lead to symptoms, such as fever. This does not mean the person is infected with the virus. Learn more from the CDC about how COVID-19 vaccines work.
It typically takes two weeks for the body to build immunity after vaccination. That means it’s possible a person could be infected with the virus that causes COVID-19 just before or just after vaccination and get sick. This is because the vaccine has not had enough time to provide protection.
Will I be required to get the vaccine in order to go to work or school?
While the vaccine will not be made mandatory nationwide or statewide, employers and schools can require people who will be working and learning in their buildings to receive the COVID-19 vaccine. COVID-19 would not be the first vaccine to be mandated in certain spaces. Many healthcare employers require the annual flu vaccine and most schools require students to receive the recommended childhood vaccines. A COVID-19 vaccine could also be required for international travel. Check with your individual employer, school, airline, or other institution for specific information on their policies.
If I have already had COVID-19 and recovered, do I still need to get the COVID-19 vaccine?
Yes, you should get vaccinated regardless of whether you already had COVID-19. There is not enough information currently available to say if or for how long after infection someone is protected from getting COVID-19 again. Early evidence suggests that this protection may not last very long, but it seems to vary by individuals.
If you were treated for COVID-19 with monoclonal antibodies or convalescent plasma, you should wait 90 days before getting a COVID-19 vaccine. Talk to your doctor if you are unsure what treatments you received or if you have more questions about getting a COVID-19 vaccine.
If I currently have COVID-19, should I get the vaccine now?
If someone currently has active symptoms of COVID-19, it is recommended that they wait to get vaccinated until they have recovered and met the criteria for ending isolation.
Will a COVID-19 vaccine need to be given every year?
While testing has ensured that the COVID-19 vaccine is safe and effective at preventing illness in the short-term, we currently do not know how long its protection will last. It is possible that protection will last for many years, but it is also possible that a COVID-19 vaccine will need to be given again in future years. Repeat vaccination could be necessary if the vaccine’s protection decreases over time or if the virus that causes COVID-19 changes over time, such as the virus that causes the seasonal flu.
Will getting a flu vaccine protect me against COVID-19?
A flu vaccine will NOT protect you from getting COVID-19, but it can prevent you from getting influenza (flu) at the same time as COVID-19. This can keep you from having a more severe illness. While it’s not possible to say with certainty what will happen in the winter, it’s likely that flu viruses and the virus that causes COVID-19 will both be spreading during that time. That means that getting a flu vaccine is more important than ever to protect your health and prevent hospitals from becoming overcrowded with flu patients and COVID-19 patients.
What are the ingredients in vaccines?
Today’s vaccines use only ingredients that are safe and effective. Each ingredient in a vaccine serves a specific purpose. For example, vaccine ingredients may:
- Help provide immunity (protection) against a specific disease
- Help keep the vaccine safe and long lasting
- Be used during the production of the vaccine
Ingredients provide immunity-
Vaccines include ingredients to help your immune system respond and build immunity to a specific disease. For example:
- Antigens are very small amounts of weak or dead germs that can cause diseases. They help your immune system learn how to fight off infections faster and more effectively. The flu virus is an example of an antigen.
- Adjuvants, which are in some vaccines, are substances that help your immune system respond more strongly to a vaccine. This increases your immunity against the disease. Aluminum is an example of an adjuvant.
- Messenger ribonucleic acid (mRNA), in some new COVID-19 vaccines, is the active component that generates an immune response in the recipient. The mRNA instructs the body to create a copy of the COVID-19 virus protein, which generates an immune response against the virus. The Pfizer and Moderna COVID vaccines are examples of mRNA vaccines.
Ingredients keep vaccines safe and long lasting-
Some ingredients help make sure a vaccine continues to work like it’s supposed to and that it stays free of outside germs and bacteria. For example:
- Preservatives protect the vaccine from outside bacteria or fungus. Today, preservatives are usually only used in vials (containers) of vaccines that have more than 1 dose. That’s because every time an individual dose is taken from the vial, it’s possible for harmful germs to get inside. Most vaccines are also available in single-dose vials and do not have preservatives in them.
- Stabilizers, like sugar or gelatin, help the active ingredients in vaccines continue to work while the vaccine is made, stored, and moved. Stabilizers keep the active ingredients in vaccines from changing because of something like a shift in temperature where the vaccine is being stored.
Ingredients used during the production of vaccines-
Some ingredients that are needed to produce the vaccine are no longer needed for the vaccine to work in a person. These ingredients are taken out after production so only tiny amounts are left in the final product. The very small amounts of these ingredients that remain in the final product aren’t harmful. Examples of ingredients used in some vaccines include:
- Cell culture (growth) material, like eggs, to help grow the vaccine antigens.
- Inactivating (germ-killing) ingredients, like formaldehyde, to weaken or kill viruses, bacteria, or toxins in the vaccine.
- Antibiotics, like neomycin, to help keep outside germs and bacteria from growing in the vaccine.
The claim that these vaccines contain a microchip or tracker is FALSE. The claim that these vaccines contain mercury is also FALSE.
For more information about the ingredients and possible allergens, please ask your provider before getting the vaccine.
For more information: https://www.vaccines.gov/basics/vaccine_ingredients
Does the COVID-19 vaccine contain aluminum?
The Pfizer and the Moderna vaccines do NOT contain aluminum.
A very small amount of aluminum is used as an ingredient in some vaccines because it helps our immune system to respond more strongly to the vaccine. For decades, vaccines that include aluminum have been tested for safety — these studies have shown that using aluminum in vaccines is safe.
Please follow the links below for more information:
Vaccines.gov (U.S. Department of Health & Human Services)
The United States Center for Disease Control and Prevention
New York Times COVID-19 Vaccine Resources
This material was curated by Viswanath Lab of Harvard Chan School of Public Health and the Dana-Farber Cancer Institute (DFCI) with the help of the Health Communication Core of Dana-Farber/Harvard Cancer Center (DF/HCC). These are not the official views of Harvard Chan or DFCI. For any questions, comments or suggestions reach out to firstname.lastname@example.org.