Understanding the New COVID-19 Vaccines: FAQs on Pfizer and Moderna's EUA

Updated 12.18

On December 11, the FDA granted Emergency Use Authorization for Pfizer's COVID-19 Vaccine. As FDA Commissioner Stephen M. Hahn MD said, "The FDA’s authorization for emergency use of the first COVID-19 vaccine is a significant milestone in battling this devastating pandemic that has affected so many families in the United States and around the world.” Now that Moderna's vaccine received Emergency Use Authorization on December 18, even more vaccines will become available.  But what does this mean for you and your employees? As the  market leader in COVID-19 solutions, we answer all of your questions about Pfizer and Moderna's vaccines.


Is one vaccine better than another?

No, they are both highly effective vaccines that use similar technology and have similar safety data. We recommend taking whichever vaccine is offered to you. 

Note that both doses must come from the same manufacturer; if you receive a first dose of the Pfizer vaccine, the second dose must also come from Pfizer. Similarly, if you receive a first dose of the Moderna vaccine, the second dose must also come from Moderna.

What are the key differences between Moderna and Pfizer’s vaccines?

If I’m young, healthy, and not at risk for COVID-19, why would I need a vaccine if I’d probably recover from the virus?

The danger of getting sick with COVID-19 far outweighs the risks of getting the vaccine; vaccination is safe, and it will prevent you from developing symptoms and experiencing serious complications caused by the virus. Although it is rarer for young, healthy individuals to die from COVID-19, no one can guarantee how your body will respond to the virus. Moreover, younger populations who have been infected with COVID-19 have reported chronic issues, and you may be unaware of certain underlying conditions that may complicate your recovery. 

Healthy individuals also make up a large portion of the population, so if all healthy individuals abstain from getting vaccinated, we will never reach herd immunity and end the pandemic. Studies are also being conducted to see if these vaccines will prevent the spread of COVID-19 in addition to the onset of disease, which would provide evidence that the vaccine not only protects you, but also your loved ones.  

Who will receive the vaccines first?

Although the CDC outlined a recommendation for who should receive the vaccine first, each state’s top health officials and governors can alter the distribution plan based on their local needs. As outlined in the graphic below, healthcare personnel and long-term care facilities will likely receive the vaccines first. Note that states do not need to vaccinate everyone in each priority group before moving to the next group. 

Due to the limited supply, healthy individuals under the age of 65 will probably not be able to get vaccinated until at least May or June of 2021 if all goes well.

CDC COVID-19 Vaccine Distribution Timeline

How many doses are required for Pfizer and Moderna?

Pfizer’s vaccine requires two shots taken 21 days apart, and Moderna’s vaccine requires two shots taken 28 days apart. Remember, both doses of the Pfizer and Moderna vaccine must come from the same manufacturer;  they are not interchangeable. 

If you only take one dose, you will not develop full immunity to COVID-19.  Therefore, not showing up to your second appointment could undermine vaccination efforts. Although it is unlikely, the novel coronavirus could even become vaccine-resistant if millions of people only take one dose of a vaccine that requires two.

What are the side effects?

The majority of participants have reported no serious side effects for both Moderna and Pfizer’s vaccines. However, some participants have reported fatigue, a headache, fever, and soreness at the injection site. These mild side effects are common for other vaccines too, and they only last a day or two. If you experience similar side effects, you should not panic; you should interpret it as a sign that your body is starting to produce an immune response. If you want extra peace of mind, contact an Eden Health provider. 

Pfizer is also aware of the two individuals in the UK who had a history of anaphylactoid reaction and responded adversely to the Pfizer vaccine. The individuals have since recovered, and a full investigation is being conducted to determine the cause. Allergic reactions occur with other vaccines too, such as the flu shot, and are extremely rare. If you have a history of severe allergic reactions to any of Pfizer’s vaccine ingredients, consult your Eden Health provider before getting vaccinated. Given that Moderna uses the same mRNA technology as Pfizer, similar precautionary measures may be recommended for Moderna’s vaccine until more information is gathered. Moderna and Pfizer will continue to monitor both of their vaccines, and we will keep you informed with any updates.

Can I get COVID-19 from the vaccines? 

No. The vaccines use non-infectious genetic material, called messenger RNA, which cannot cause a COVID-19 infection.

If you notice COVID-19 symptoms after getting vaccinated, should you isolate? 

Yes. Because it takes a few weeks to build up immunity after receiving the vaccines, it is possible to become infected with COVID-19 right before (or after) vaccination. This could happen because you have not had both doses of the vaccine or the vaccine has not had sufficient time in your body to provide protection. If this occurs, you should contact your Eden Health Care Team, explain your symptoms, and isolate accordingly.

Would people who have recovered from COVID-19 still benefit from getting the vaccines?

Yes. It seems the natural immunity that occurs after you recover from the virus is not as strong as the immunity you develop after getting the Pfizer or Moderna vaccine. Immunity levels appear to differ in people who were infected with the virus. For people who were mildly ill with the novel coronavirus, their immunity may diminish after a few months. For others, it may last longer. With a vaccine, we can control the dosage and guarantee that it will elicit an optimal immune response – a variable you cannot control in a natural infection.

Now that vaccines are available, do we still need to wear masks and socially distance?

Yes, these measures are still necessary to slow the spread of COVID-19, especially now. It will take months before the vaccines are widely available, and we will need to take extra precautions until everyone can get vaccinated. 

It’s also unknown whether vaccinated individuals are less likely to transmit the virus. If these people can unknowingly spread COVID-19, masks and social distancing will continue to be critical tools in protecting others. Additionally, active monitoring of symptoms and exposures and accessible COVID-19 testing are still important for mitigating the spread of the virus.

What populations were not included in Pfizer and Moderna’s clinical trials? 

Some subsets of the population such as pregnant patients and children under 12 years of age have not been enrolled in Pfizer’s vaccine trials to date. Similarly, Moderna’s vaccine trials have not included pregnant women and children under 18 years of age. 

It is important to note that the current lack of data does not indicate increased suspicion from researchers and physicians about adverse effects in these populations. In fact, pregnant patients routinely receive vaccinations for illnesses such as the flu during their pregnancies. If you are pregnant and want extra guidance, the American College of Obstetricians and Gynecologists (ACOG) suggests consulting your medical provider before getting vaccinated against COVID-19.

What populations are eligible for vaccination under the EUA? 

Pfizer’s emergency use authorization includes individuals 16 years old and older. Moderna’s emergency use authorization includes individuals 18 years and older.

Will the vaccines cure coronavirus in those already infected? 

No. As with most vaccines, a COVID-19 vaccine will only help prevent symptom development in people who are exposed to the virus. However, other medicines are being tested and developed to treat patients currently infected with COVID-19. 


While this news is exciting, we still have months before the vaccines will be widely available. And even when the vaccines are accessible to everyone who wants it, majority of the population needs to get vaccinated in order for the pandemic to end. Until then, we need to use other tools to help reduce the spread of the virus. For more information on COVID-19 vaccines, visit our blog post about emergency use authorizations



Emergency Use Authorization for Vaccines to Prevent COVID-19 (US Food & Drug Administration)

8 Things to Know about Vaccine Planning (CDC)

Pfizer and BioNTech to Submit Emergency Use Authorization Request Today to the U.S. FDA for COVID-19 Vaccine (Pfizer)

How CDC Is Making COVID-19 Vaccine Recommendations (CDC)

FDA Takes Key Action in Fight Against COVID-19 By Issuing Emergency Use Authorization for First COVID-19 Vaccine (US Food & Drug Administration)


Disclaimer: This information is based on current resources available and is subject to change. This document and its contents are provided for informational purposes only, and not intended to be, and should not be understood or treated as, a substitute for professional medical advice around COVID-19, its risks or symptoms, or to take the place of any local, state and national laws and guidelines around COVID-19. Always seek the advice of a physician or other qualified health provider with any questions you may have regarding a medical condition.

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