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COVID-19 Vaccines: Questions and Answers

COVID 19 vaccineCOVID-19 Vaccines: Questions and Answers
Multiple vaccines against coronavirus disease 2019 (COVID-19, otherwise known as the SARS-CoV-2 virus) had originally been developed, tested and released under what is known as an Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA) in the fight against COVID-19. This incredibly important development began less than 10 months after the World Health Organization (WHO) declared COVID-19 a worldwide pandemic on March 11, 2020, and within two years likely saved tens of millions of lives globally. Those vaccines that remain on the market in the United States are now fully FDA-approved and all prior EUA’s have been revoked. 

All of the COVID-19 vaccines that remain on the market are for use in people 65 and older. For younger people, FDA indications stress the need for one or more high risk conditions to be eligible. High risk conditions for the COVID vaccines in this context include liver, heart and kidney disease, lung diseases (such as COPD or moderate to severe asthma), cancer, certain disabilities, immunodeficiencies and obesity. However, a recent statement by the Advisory Committee on Immunization Practices (ACIP) suggests that these vaccines can be given to younger people in the context of shared decision making between the patient and their provider. 

Of the COVID-19 vaccines on the market, the vaccine by Pfizer/BioNTech (Comirnaty®) is indicated in those 5 years and older, the Moderna vaccine (Spikevax®) is for those 6 months and older, and a newer Moderna vaccine (mNexspike™) is for those 12 years and older. Finally, the vaccine (Nuvaxovid™) by Novavax, a non-mRNA vaccine, has been approved for those 12 years and older.  

The mRNA vaccines by Pfizer/BioNTech and Moderna make the body form an immune response in a similar fashion. A small portion of viral protein is encoded on the mRNA and delivered to the body with instructions on how to make proteins found in the virus. Cells make this protein and display it on their surface. The immune system then makes antibodies to this protein because it is recognized as foreign. That way, if the immune system encounters the COVID-19 virus in the future, the pre-made antibodies and other immune pathways will defend the body from infection. Protein subunit vaccines such as the Novavax vaccine use the traditional method of introducing foreign protein directly into the body, allowing for an immune response.

Understandably, many questions come to light surrounding the mechanisms of these vaccines.

Are these vaccines considered safe?
Studies of these vaccines have shown significant efficacy in preventing emergency room visits, hospitalizations and deaths. It has been clearly shown that the patients receiving the active vaccines were much less likely to become infected by COVID-19. Of the small number of patients that did become infected, they were far less likely to get severe infection or to be hospitalized. 

The most common side effects of the vaccines included pain and redness at the site of the injection in the arm, and sometimes systemic symptoms like fever, chills, fatigue or a headache that lasted a few days.

Do the vaccines contain live virus?
The vaccines do not contain any live virus, so you cannot get COVID-19 from the vaccine. And even though the vaccines use the concept of mRNA so that our cells make the ‘spike-protein’, this genetic material does not enter the nucleus of the cells and does not incorporate itself into our own genes or change our DNA. After making the protein, the new genetic material is destroyed.

I know or think I may have already had COVID-19. Should I still receive the vaccine?
People who have already had COVID-19 or suspect they may have been infected should still get the vaccine. It is not fully known how long the immunity of natural infection lasts, so the vaccine should help in further reducing the risk of reinfection. It is recommended that people are asymptomatic and finish their isolation before receiving the vaccine. 

I have an immunodeficiency. Can I still receive the vaccine?
The current mRNA vaccines do not contain live virus, so there is no risk of infection. If you have a primary or secondary immunodeficiency, or are taking medications to suppress the immune system, they simply may not work as well. As the Novavax vaccine contains only recombinant protein nanoparticles there is no live COVID-19 virus in this vaccine.

You should speak to your treating physician about receiving any of these vaccines to see which of the vaccines may be most appropriate. 

I have allergies. Can I still receive the vaccine?
There have been several cases in the media of patients having allergic reactions to the vaccines. Severe allergic reactions to any vaccine are possible but are very rare. It is not yet clear what caused the allergic reaction in these cases but patients with prior allergic to these vaccines or components of these vaccines should speak with their physician. 
Patient with allergies to food, latex, insect stings or inhalant allergens are not thought to be at increased risk of an allergy to these vaccines.

I’m pregnant. Can I still receive the vaccine?
Evidence of vaccine safety in pregnant or lactating women has been well documented. The American College of Obstetricians and Gynecologists recommend vaccination for all people who are pregnant, breastfeeding, trying to get pregnant now or might become pregnant in the future. MothertoBaby, a research partner of the AAAAI, has more information on the vaccine in pregnant and lactating women at mothertobaby.org.

COVID-19 VACCINES: QUICK SUMMARY

Four vaccines are now available to stop people from getting sick with the COVID-19 virus, 3 based on mRNA technology and one protein-based, non-mRNA formulation. 

Are these vaccines safe?
All of these vaccines are safe and work very well. It was shown that the patients who had the vaccines were much less likely to catch the COVID-19 virus. Of the small number of patients that did get the virus, they were far less likely to get severely ill.

Side effects of the vaccines included pain and redness at the site of the injection in the arm, and sometimes symptoms like fever, chills, tiredness or a headache that may last a few days.

Do the vaccines contain live virus?
The vaccines do not contain any live virus, so you cannot get COVID-19 from the vaccine. They also don’t make any changes to our own genes.
 
I know or think I may have already had COVID-19. Should I still receive the vaccine?
People who know or think that they have had COVID-19 before should still get the vaccine. These vaccines should help reduce the risk from getting sick again. If you are still sick from COVID-19, you should wait until you feel better before getting the vaccine.

I have allergies. Can I still receive the vaccine?
There have been some cases in the media of patients having allergic reactions to these vaccines. Severe allergic reactions to any vaccine are possible but are very rare. Patients who are known to be allergic to any components of the vaccines should NOT receive them.

Patient with allergies to food, latex, insect stings or environmental allergens are not at a higher risk of allergic reaction.

If you have any concerns about your own risk for an allergic reaction to the COVID-19 vaccines, or you have a disease such as an immune deficiency, speak with your allergist or your treating physician to see if you can safely receive them.

The AAAAI's Find an Allergist / Immunologist service is a trusted resource to help you find a specialist close to home.

10/1/2025