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COVID-19 Vaccines: Questions and Answers

COVID 19 vaccinesIn a remarkable feat of science, multiple vaccine candidates against coronavirus disease 2019 (COVID-19, otherwise known as the SARS-CoV-2 virus) have been developed, tested and now released under what is known as an Emergency Use Authorization (EUA) by the Food and Drug Administration (FDA). This incredibly important development in the fight against COVID-19 occurs less than 10 months since the World Health Organization (WHO) declared COVID-19 a worldwide pandemic on March 11, 2020.

An EUA refers to the FDA allowing unapproved medical products or unapproved uses of approved medical products to be used in an emergency public health situation when there are no adequate, approved, and available alternatives. The two vaccines that have been authorized to date include a vaccine by Pfizer-BioNTech, which was granted this status on December 11, 2020, for patients 16 years and older, given in two injections spaced 3 weeks apart and a second vaccine by Moderna, on December 18, 2020, for patients 18 years and older, given in two injections spaced 4 weeks apart.

Both vaccines are known as mRNA (messenger RNA, a nucleic acid that contains genetic material) vaccines because of how they make the body form an immune response. A small portion of viral protein is encoded on the mRNA and delivered to the body with instructions in 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.

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

Under an EUA, are these vaccines still considered safe?
Even though the FDA has authorized release of these vaccines through an EUA, they are still considered safe. The same rigorous phase 3 testing is necessary to show that they meet standards of both efficacy and safety in patients, as is true with other approved vaccines.

Studies of both vaccines have shown a greater than 90% efficacy in a diverse population of more than 70,000 participants. These trials were placebo controlled, meaning that some patients received the active vaccine, while others received the placebo. It was clearly shown that the patients receiving the active vaccine 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.

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 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. And even though the vaccines use the novel 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. After making the protein, the mRNA 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 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 finish their isolation before receiving the vaccine.

We also know that people who have had COVID-19 are at very low risk of reinfection in the first 90 days after infection, so if a person has had COVD-19 in the last 90 days, they may want to wait until more vaccine is available.

I have an immunodeficiency. Can I still receive the vaccine?
The current 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. There is not enough data to know how well the vaccines work in these cases, so you may wish to speak with your treating physician.

I have allergies. Can I still receive the vaccine?
There have been several cases in the media of patients having allergic reactions to the Pfizer-BioNTech vaccine. 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. One additional ingredient to this vaccine is a compound known as polyethylene glycol. This material has many uses in the medical industry. Most commonly it is used as a laxative. Patient who are known to be allergic to polyethylene glycol should NOT receive the vaccine.

Patient with allergies to food, latex, insect stings or inhalant allergens are not thought to be at increased risk of an allergy to this vaccine.

The Centers for Disease Control and Prevention (CDC) already has several recommendations regarding the administration and management of allergic reactions to the Pfizer-BioNTech vaccine. These include:

  • Those with a history of severe allergic reaction (e.g., anaphylaxis) to an injectable medication or other vaccine should use caution when receiving the vaccine and be observed during a 30-minute observation period.
  • Those with a history of severe allergic reaction to any component of the Pfizer-BioNTech COVID-19 vaccine (including polyethylene glycol) should not be vaccinated with the Pfizer-BioNTech COVID-19 vaccine.
  • In all cases, the vaccine should be administered in a healthcare setting where severe allergies (e.g., anaphylaxis) can be treated. Epinephrine is the first-line treatment for anaphylaxis and should be readily available.


If you have any concerns regarding your own risk for an allergic reaction to the COVID-19 vaccines, speak with your allergist.

Additional Questions
There are still many questions related to vaccines against COVID-19. It’s not yet clear how long immunity from these vaccines will last against COVID-19, and it’s also not clear at the present time if the vaccines prevent transmission of the disease. For these reasons, it is still recommended that people continue to wear masks and physically distance even when vaccinated.

There are also no safety data in pregnant or lactating women. The CDC’s Advisory Committee on Immunization Practices (ACIP) and the American College of Obstetricians and Gynecologists (ACOG) recommend that vaccination should not be withheld from pregnant or lactating women, but they should be informed there are insufficient safety data available at this time. You should speak to your physician about the risks and benefits of vaccination in these cases. In addition, contact MotherToBaby, a research partner of the AAAAI, for more information on the vaccine in pregnant and lactating women, at mothertobaby.org.

There are also many more vaccine candidates on the horizon, and with very different mechanisms of action compared to the two vaccines that are currently authorized. Each will have their own recommendations and safety data. Yet hopefully as more of the population gets vaccinated, starting with our front-line workers and long-term care residents, the number of infections in the population will begin to slow and many lives will be saved.

This article has been reviewed by Andrew Moore, MD, FAAAAI

Reviewed: 1/4/20

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