By Ivy Sandquist, MS, and Jonathan Beatty, MD
Ms. Sandquist has a Master of Science degree in Microbiology and Immunology from Tulane School of Medicine. She is currently an MD candidate, Tulane SOM, class of 2022.
Dr. Beatty is a psychiatrist in private practice in Philadelphia, Pennsylvania.
Note: This article is up-to-date as of January 26, 2021
Even clinicians who are not experts on COVID-19 vaccination are asked questions about it by patients and others. Everyone needs to get involved in disseminating scientifically accurate information about these vaccines.
So, on this page, we will provide a brief, “simple and practical” guide to COVID-19 vaccines available in the US as of January 26, 2021. Specifically, we will briefly cover the efficacy, safety, vaccine approval process, and compare the COVID-19 vaccines to other currently available vaccines.
As everyone knows by now, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes coronavirus disease or COVID-19 named for its emergence in December 2019. COVID-19 can cause serious or life-threatening disease, including severe respiratory illness, multisystem organ damage, memory or concentration problems, and chronic fatigue (1,2,3). More information on COVID-19, the current pandemic, and the available tests for COVID-19 infection can be found in our recommended resources below.
What are the currently available Covid-19 Vaccines?
As of January 2021, two vaccines are available in the US to protect against infection with COVID-19.
1. Pfizer-BioNTech COVID-19 Vaccine
2. Moderna Covid-19 Vaccine
These vaccines were approved in December 2020 by the FDA via an Emergency Use Authorization (4,5). More vaccines will continue to become available in the coming months as they pass the emergency use approval process. Physicians can stay up to date on available vaccines through the WHO and FDA websites.
How do the COVID-19 vaccines work?
Currently available vaccines contain messenger RNA (mRNA) wrapped in lipid droplets (4,5). Here’s the briefest possible explanation of how these mRNA-based vaccines work.
The mRNA in the vaccine is identical to mRNA present in the virus where it codes for a part of protein present on the surface of the virus. This protein is called the called the S or Spike glycoprotein protein. The reason this S protein is important to the virus is because it helps the virus to fuse with a person’s cells and to enter them.
The mRNA-based vaccines aim to get our immune cells to produce antibodies to this S protein. How?
1. When a person gets the mRNA-based vaccine, the mRNA is released into the body.
2. The human cells use this mRNA to produce the S protein that is identical to that on the SARS-CoV-2 virus (2).
3. This S protein, produced in the person’s body, is then taken up by their immune cells.
4. The immune cells produce antibodies to the S protein.
5. If this vaccinated person is later exposed to the SARS-CoV-2 virus, the antibodies block the virus from entering the person’s cells.
What else is in the vaccines?
We should also let persons who have concerns about the vaccine know that:
1. Other than the mRNA wrapped in lipid droplets, these vaccines only contain substances that are common components of any vaccine.
Other components of the Pfizer-BioNTech vaccine include phosphate buffer solution (PBS), sucrose, sodium chloride (salt), and water.
Other components of the Moderna vaccine include tromethamine (tris buffer), sodium acetate, sucrose, and water.
2. There are no food allergy derivatives, aluminum, mercury, or preservatives in these vaccines (4,5).
Important! TWO doses are needed
It is important for people to get a second dose of the Pfizer vaccine three weeks after the first dose or of the Moderna vaccine four weeks after the first dose. This second dose allows for a person’s body to increase the number and specificity of antibodies for faster recognition of the virus.
It is important for patients to know they are not fully protected from the virus until one week after the second dose.
How well do these vaccines protect against COVID-19?
The efficacy of both vaccines has currently been tested in over 30,000 people per vaccine (6,7).
In clinical trials, both these vaccines showed approximately 95% effectiveness against severe COVID-19 symptoms at one week after the second dose.
Who can get the Covid-19 vaccine?
The Pfizer-BioNTech and Moderna COVID-19 vaccines are currently approved under the FDA’s Emergency Use Authorization for anyone over the age of 16 or 18, respectively.
The vaccines are contraindicated in anyone who is currently acutely ill or with a past medical history of a severe allergic reaction (anaphylaxis) to any ingredient in the vaccine.
The vaccines are not contraindicated in those who have well-controlled HIV (4, 5, 8).
Should people who have had COVID-19 still get vaccinated?
Yes, it is recommended that people who had COVID-19 infection and have recovered should still receive a COVID-19 vaccine. Why? Because there is some preliminary evidence that immunity to COVID-19 from having had the infection may not be long-lasting.
How long does immunity after vaccination last?
The duration of immunity after vaccination is not known yet. Persons who participated in the clinical trials are still being followed to find out more about this.
But, preliminary data from the Moderna vaccine showed protective levels of antibodies at least three months after vaccination (9).
How were these vaccines approved?
Compared to the traditional approval and licensing process by the FDA, the COVID-19 vaccines were approved more quickly (due to requiring fewer participants and less time than standard licensing requirements) under an Emergency Use Authorization (EUA). EUAs allow for the FDA to expedite the approval of the use of medicines and vaccines that act as countermeasures in the case of a disease that can affect national security or the health and safety of the citizens of the United States.
But, this doesn’t mean that these vaccines have not undergone rigorous scientific testing similar to FDA licensed vaccines. Prior to approving these vaccines for public use, the vaccines were shown in what are called phase 1 and phase 2 clinical trials to be safe, and in large phase 3 clinical trials to be effective compared to placebo at two months after vaccination.
How were the vaccines created quickly?
These vaccines were created in record time not only because they were given top priority and considerable resources were allocated to their creation. Much of the research related to creating the COVID-19 vaccine had been underway for years prior to the pandemic.
For example, the S protein was chosen as the target for the vaccine because it has been known for nearly a decade that this component of SARS viruses causes an immune reaction during the disease progression, which made the S protein an ideal candidate for being targeted by a vaccine (12).
Also, mRNA vaccines have been under development for other viruses even before the pandemic (13,14).
How do the Covid-19 vaccines compare to other vaccines?
In currently FDA licensed vaccines, this is done by taking either an attenuated live virus or bacteria, a killed version of the virus or bacteria, or by isolating a part of the bacteria or virus for use in vaccination. Injection of these weaker or incomplete parts of the infectious agent allow the body to create immune protection without the danger of infection.
The difference between the COVID-19 vaccines and others is that rather than wait for the virus to replicate in a lab and then isolating the proteins (such as what we do for the flu vaccine) scientists were able to use the sequenced genome of the virus and isolate the code for the surface protein on the virus (6,7). By creating an mRNA rather than isolating the protein individually from the virus to make the vaccine, scientists were able to create a faster and cleaner approach to making the protein.
What side effects can occur?
Like all available vaccines, there are some known possible side effects of vaccination.
The most common side effects of COVID-19 vaccines include (4,5):
– Pain, swelling, or redness at the injection site
– Fatigue, headache, muscle or joint pain
– Nausea/ vomiting, and
– Low-grade fever or chills.
More information on what to expect after vaccination can be found HERE.
There have been very few severe reactions to the vaccines, and these are being monitored on an ongoing basis (10,11). The COVID-19 vaccines can also be associated with allergic reactions, including severe anaphylaxis. The CDC recommends that anyone with a known allergy to polyethylene glycol (a lipid in the vaccines) or polysorbate (not in the vaccines but a related substance) should not get an mRNA Covid-19 vaccine (15). After receiving a COVID-19 vaccine, the person is monitored for about 15 minutes for any signs of a severe allergic reaction.
Since mRNA can only get into the cytoplasm of cells and cannot enter the nucleus, it cannot bind to the DNA of human cells.
The vaccine does not contain the virus and the mRNA can only produce one protein from the virus. It is impossible to get COVID-19 from one of these vaccines.
– These side effects and adverse reactions are not unique to the COVID-19 vaccines. They are all known to occur with other vaccines (16).
– Based on current clinical data and safety practices, COVID-19 vaccine is known to be as safe or safer than other available vaccines.
Anyone who receives the COVID-19 vaccines is encouraged to sign up with the CDC’s vaccine health checker program v-safe.
1. Mayo Clinic. Covid-19 (coronavirus): Long term effects. November 17, 2020.
2. Dong Y, Dai T, Wei Y, Zhang L, Zheng M, Zhou F. A systematic review of SARS-CoV-2 vaccine candidates. Signal Transduct Target Ther. 2020 Oct 13;5(1):237. doi: 10.1038/s41392-020-00352-y. PMID: 33051445; PMCID: PMC7551521.
3. Carfì A, Bernabei R, Landi F; Gemelli Against COVID-19 Post-Acute Care Study Group. Persistent Symptoms in Patients After Acute COVID-19. JAMA. 2020 Aug 11;324(6):603-605. doi: 10.1001/jama.2020.12603. PMID: 32644129; PMCID: PMC7349096.
4. Food and Drug Administration (FDA). Moderna Covid-19 Vaccine. Updated January 6, 2021.
5. Food and Drug Administration (FDA). Pfizer-BioNTech Covid-19 Vaccine. Updated December 29,2020.
6. Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, Perez JL, Pérez Marc G, Moreira ED, Zerbini C, Bailey R, Swanson KA, Roychoudhury S, Koury K, Li P, Kalina WV, Cooper D, Frenck RW Jr, Hammitt LL, Türeci Ö, Nell H, Schaefer A, Ünal S, Tresnan DB, Mather S, Dormitzer PR, Şahin U, Jansen KU, Gruber WC; C4591001 Clinical Trial Group. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med. 2020 Dec 31;383(27):2603-2615. doi: 10.1056/NEJMoa2034577. Epub 2020 Dec 10. PMID: 33301246; PMCID: PMC7745181.
7. Baden LR, El Sahly HM, Essink B, Kotloff K, Frey S, Novak R, Diemert D, Spector SA, Rouphael N, Creech CB, McGettigan J, Kehtan S, Segall N, Solis J, Brosz A, Fierro C, Schwartz H, Neuzil K, Corey L, Gilbert P, Janes H, Follmann D, Marovich M, Mascola J, Polakowski L, Ledgerwood J, Graham BS, Bennett H, Pajon R, Knightly C, Leav B, Deng W, Zhou H, Han S, Ivarsson M, Miller J, Zaks T; COVE Study Group. Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine. N Engl J Med. 2020 Dec 30. doi: 10.1056/NEJMoa2035389. Epub ahead of print. PMID: 33378609.
8. Center for Disease Control. Facts about the Covid-19 Vaccines. Updated Jaunary 4, 2021.
9. Widge AT, Rouphael NG, Jackson LA, Anderson EJ, Roberts PC, Makhene M, Chappell JD, Denison MR, Stevens LJ, Pruijssers AJ, McDermott AB, Flach B, Lin BC, Doria-Rose NA, O’Dell S, Schmidt SD, Neuzil KM, Bennett H, Leav B, Makowski M, Albert J, Cross K, Edara VV, Floyd K, Suthar MS, Buchanan W, Luke CJ, Ledgerwood JE, Mascola JR, Graham BS, Beigel JH; mRNA-1273 Study Group. Durability of Responses after SARS-CoV-2 mRNA-1273 Vaccination. N Engl J Med. 2021 Jan 7;384(1):80-82. doi: 10.1056/NEJMc2032195. Epub 2020 Dec 3. PMID: 33270381; PMCID: PMC7727324.
10. Food and Drug Administration (FDA). Vaccine Development-101. Updated December 14, 2020.
11. Food and Drug Administration (FDA). Emergency Use Authorization for Vaccines Explained. November 20, 2020.
12. Bisht H, Roberts A, Vogel L, Bukreyev A, Collins PL, Murphy BR, Subbarao K, Moss B. Severe acute respiratory syndrome coronavirus spike protein expressed by attenuated vaccinia virus protectively immunizes mice. Proc Natl Acad Sci U S A. 2004 Apr 27;101(17):6641-6. doi: 10.1073/pnas.0401939101. Epub 2004 Apr 19. PMID: 15096611; PMCID: PMC404098.
13. Iavarone C, O’hagan DT, Yu D, Delahaye NF, Ulmer JB. Mechanism of action of mRNA-based vaccines. Expert Rev Vaccines. 2017 Sep;16(9):871-881. doi: 10.1080/14760584.2017.1355245. Epub 2017 Jul 28. PMID: 28701102.
14. ClinicalTrials.gov. Safety, reactogenicity, and Immunogenicity of Cytomegalovirus Vaccines mRNA-1647 and mRNA-1443 in Healthy Adults. Last accessed Jaunary 10, 2021.
15. Center for Disease Control (CDC). Allergic Reactions. Updated December 31, 2020.
16. Vaccines.gov. Vaccine Side Effects. February 2020.
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Disclaimer: The content on this website is provided as general education for medical professionals. It is not intended or recommended for patients or other laypersons or as a substitute for medical advice, diagnosis, or treatment. Patients must always consult a qualified health care professional regarding their diagnosis and treatment. Healthcare professionals should always check this website for the most recently updated information.A Physician’s Guide for Frequently Asked Questions on the Covid-19 Vaccines