Frequently Asked Questions about COVID-19 Vaccines

Updated on May 20, 2021

As the COVID-19 vaccines are introduced, many people have questions about their 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 (WHO), the Ministry of Health and Family Welfare, Government of India (MoHFW), the United States Centers for Disease Control and Prevention (CDC), 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. Here is a illustrative guide to COVID-19 appropriate behaviours published by the MoHFW.

If you cannot find the information you are looking for on this page, you are invited to submit your own questions through this form and our team will look into the answers.


Vaccine Development

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:

  • 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.
  • 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.
  • 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.
  • 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.

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Why was the COVID-19 vaccine developed so much faster than other vaccines?

The vaccine 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. Steps to ensure safety have not been eliminated.

Vaccine Safety

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.

Vaccine Development

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 reaction to other vaccines or injectables, it is recommended that you speak to your doctor before getting vaccinated.

Updated Is it safe for me to get the vaccine if I am pregnant or breastfeeding?

At present, there are no data available on vaccination with Covishield or Covaxin for pregnant women, because pregnant women have been excluded from these vaccine clinical trials. Experts are determining safety for pregnant women through studies on women who were part of clinical trials and later became pregnant. Currently the MoHFW does not advise women who are pregnant or not sure of their pregnancy to receive the COVID-19 vaccine.

The MoHFW recommends COVID-19 vaccination for all lactating women.


NEW Can COVID-19 vaccine cause infertility in men or women?

There is no scientific evidence to suggest that the COVID-19 vaccine could cause infertility in women or in men. Infertility is not known to occur as a result of COVID-19 disease either.

NEW Does Covishield (Oxford/AstraZeneca) vaccine cause blood clots?

Covishield is NOT associated with an increased overall risk of blood clotting disorders. There have been very rare cases of unusual blood clots accompanied by low levels of blood platelets. They symptoms associated with the rare blood clots that require prompt medical treatment include:  breathlessness; pain in the chest or stomach; swelling or coldness in a leg; severe or persistent headaches or blurred vision; or tiny blood spots under the skin beyond the site of the injection. One should seek urgent medical attention if they have any of these symptoms in the weeks after their injection.

Serious side effects from vaccines are rare but they do occur, with any vaccine and for any disease. However, we are witnessing the largest mass vaccination campaign in history. Given the high number of people being vaccinated and the attention focused on the vaccines and the pandemic, some rare reactions are to be expected. It remains to be seen if similar concerns will be raised over other COVID-19 vaccines, but given that AstraZeneca’s was the first to be approved and has been given to far more people than any others, any rare adverse events are more likely to show up simply because of the sheer volume of people to have received it.


Vaccine Access and Cost

NEW Who is eligible for the COVID-19 vaccine?

As of May 1st, 2021, all people over 18 years are eligible for the COVID-19 vaccine. Please check your local state guidelines for more information.

If you cannot pre-register online, please contact your local government health workers, who will refer you to the government COVID Vaccination Center for on the spot registration, appointment, verification and vaccination on the same day.

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Common Concerns

NEW Why are people getting infected even after vaccination?

COVID-19 vaccines are effective. However, a small number of vaccinated individuals may still develop infection, but it is likely to be less severe. And hence it is necessary to wear a mask, wash hands and stay away from crowds. Typically, COVID-19 vaccines prevent infection, and even if some small number of people get infected, it is less serious. Vaccination, prevents infection or reduces its severity.

The reasons for why a vaccinated individual may develop COVID-19 infection:

  1. It’s possible a person could have been infected just before or just after vaccination. It typically takes about 2 weeks for the body to build protection after the second dose of vaccination. Thus, a person can get sick if the vaccine has not had enough time to provide protection.
  2. The virus that causes COVID-19 is evolving and new variants of the virus are spreading. Current data suggest that COVID-19 vaccines offer protection against most variants. However, some variants might cause illness in some people after they are fully vaccinated.
  3. A small percentage of people who are fully vaccinated will still get COVID-19 if they are exposed to the virus that causes it. These are called “vaccine breakthrough cases.” This means that while people who have been vaccinated are much less likely to get sick, it may still happen. Experts continue to study how common these cases are.

Even though vaccination will protect most people from getting sick, a small percentage of fully vaccinated people can get infected. There is evidence that vaccination may make illness less severe in people who get vaccinated but still get infected. The overall risk of hospitalization and death among fully vaccinated people will be much lower than among people with similar risk factors who are not vaccinated.


Why do I need to get two doses of the vaccine?

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.

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 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 on how the Serum Institute and Bharat Biotech vaccines work.

It typically takes a few 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.

UPDATED If I have already had COVID-19 and recovered, do I still need to get the COVID-19 vaccine?

Yes, it is advisable to receive the COVID-19 vaccine irrespective of past history of infection with COVID-19. This will help in developing a strong immune response against the disease. It is unclear whether people who have had COVID-19 and recovered will develop enough of an immune response to the illness to protect them from getting COVID-19 again. Even if there is some protection, it is unclear how long it will last. Therefore, it is recommended to receive vaccine even after COVID-19 infection.

Wait for 3 months after recovery from COVID-19 symptoms before getting the vaccine.

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If I currently have COVID-19, should I get the vaccine now?

Persons with confirmed or suspected COVID-19 infection should be in isolation for atleast 10days. They will increase the risk of spreading the virus to others at the vaccination site, hence infected individuals should defer vaccination for 14 days after symptoms resolution.

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.

UPDATED Do I need to wear a mask and avoid close contact with others if I have received two doses of the vaccine?

Yes. While experts learn more about the protection that COVID-19 vaccines provide under real-life conditions, it will be important for everyone to continue using all the tools available to us to help stop this pandemic. These tools include covering your mouth and nose with a mask, washing hands often, and staying at least 2 meters away from others. Together, the COVID-19 vaccine and everyone following the COVID-19 safety guidelines will offer the best protection from getting and spreading COVID-19.  Experts need to understand more about the protection that COVID-19 vaccines provide before deciding to change recommendations on steps everyone should take to slow the spread of the virus that causes COVID-19.

COVID-19 vaccines are effective at preventing COVID-19 disease, especially severe illness and death. But we’re still learning how well COVID-19 vaccines keep people from spreading the disease. Moreover, we’re still learning how effective the vaccines are against variants of the virus that causes COVID-19. Early data show the vaccines may work against some variants but could be less effective against others.

A small number of people may still develop infection, but it is likely to be less severe. And hence it is necessary to wear a mask, wash hands and stay away from crowds. Until we know more about the effectiveness of the vaccine against the variants, and until a majority of the population is vaccinated to reach herd (or community) immunity, it is necessary to continue to follow the COVID-19 prevention protocols.


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:

  1. Help provide immunity (protection) against a specific disease
  2. Help keep the vaccine safe and long lasting
  3. 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.
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, 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.

Composition of Covishield includes inactivated adenovirus with segments of Coronavirus, Aluminium Hydroxide Gel, L-Histidine, L-Histidine Hydrochloride Monohydrate, Magnesium Chloride Hexahydrate, Polysorbate 80, Ethanol, Sucrose, Sodium Chloride, and Disodium Edetate Dihydrate (EDTA).

Composition of Covaxin includes inactivated Coronavirus, Aluminum Hydroxide Gel, TLR 7/8 Agonist, 2-Phenoxyethanol and Phosphate Buffered Saline [NKA1].

For more information about the ingredients and possible allergens, please ask your provider before getting the vaccine.


Please follow the links below for more information:

Ministry of Health & Family Welfare. Frequently Asked Questions on COVID-19 vaccine.

World Health Organization

Center for Disease Control and Prevention

New York Times COVID-19 Vaccine Resources

Ministry of Health & Family Welfare. COVID-19 operational guidelines. Published 28 December 2020.


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