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Types of COVID-19 Vaccines

Reviewed on 12/18/2020

What Is the Vaccine for COVID-19?

There is currently no FDA-approved vaccine to prevent COVID-19, but one is authorized for use under an emergency designation. Dozens more by various companies are still in clinical trials.
There is currently no FDA-approved vaccine to prevent COVID-19 as of Dec. 2020, but one is authorized for use under an emergency designation. Dozens more by various companies are still in clinical trials.

There is currently no FDA-approved vaccine to prevent COVID-19, though candidates have been permitted because of the urgency of the pandemic crisis.

  • On December 11, 2020, the U.S. Food and Drug Administration (FDA) issued an emergency use authorization (EUA) for the Pfizer-BioNTech COVID-19 vaccine to prevent coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in individuals 16 years of age and older. Pfizer reported efficacy of 95% for their vaccine. 
  • On December 18, the Moderna COVID-19 vaccine received a EUA. Moderna reported efficacy of 94.5% for their COVID-19 vaccine.

The United Kingdom began administering the Pfizer vaccine in December 2020 and noted two people with a history of severe allergies to previous medications had an allergic reaction to the vaccine, prompting a warning for those prone to allergic reactions to avoid the vaccine until the specific components that caused the allergic reaction can be identified. Immunizations are administered by medical professionals, so treatment is immediately available in the rare case of an allergic reaction. 

I addition to Pfizer-BioNTech, other large-scale (Phase 3) clinical trials in progress for COVID-19 vaccines in the U.S. include:

  • Moderna
  • AstraZeneca
  • Janssen (Johnson & Johnson)
  • Novavax

The other vaccines are being evaluated by the FDA for emergency use authorization (EUA) but have not yet been approved for use. 

As of December 17, 2020, The New York Times Coronavirus Vaccine Tracker listed 63 vaccines in clinical trials on humans, with 18 having reached the final stages of testing. At least 85 preclinical vaccines are under active investigation in animals.

What Is an Emergency Use Authorization (EUA)?

An emergency use authorization (EUA) for a vaccine is not the same as FDA approval. It is a declaration from the FDA that circumstances exist to justify the emergency use of drugs and biological products during the COVID-19 pandemic, and in the case of the Pfizer-BioNTech COVID-19 vaccine, it has not undergone the same type of review as an FDA-approved or cleared product. 

An EUA is based on the available evidence that shows the product may be effective in preventing COVID-19 during the COVID-19 pandemic and the known and potential benefits of the vaccine outweigh the known and potential risks of the vaccine.

How Do COVID-19 Vaccines Work?

Vaccines help the body produce immunity to infection by imitating the infecting agent. Vaccines almost never cause illness, but instead boost the body’s adaptive immune function to produce T-lymphocytes and antibodies (parts of the immune system that help the body fight germs). Once the simulated infection created by the vaccine goes away, the body has a “memory” of T-lymphocytes and B-lymphocytes that remember how to fight that infection in the future.

Following an immunization, it can take several weeks for the body to produce the produce T-lymphocytes and B-lymphocytes needed to fight infection, so it is possible a person could become infected with a disease just before or just after vaccination because the body has not yet had time to build its defenses. 

After a vaccine is administered and the body is building its defenses, people may experience mild side effects from the vaccine. This is normal and expected. Common side effects and reactions to vaccines include:

There is a Vaccine Adverse Event Reporting System (VAERS) in place for patients to report unexpected vaccine side effects. https://vaers.hhs.gov/

How Do the COVID-19 Vaccines Work?

Coronaviruses, including COVID-19, are named for the crown-like spikes on their surface because corona in Latin means “crown.” The current vaccine front-runners all focus on these spikes. 

The Pfizer-BioNTech Vaccine

The Pfizer-BioNTech and Moderna mRNA vaccines use a new type of technology not used in any existing vaccine. These mRNA vaccines contain a small part of the genetic code for a harmless piece of the SARS-CoV-2 spike protein (the same spike protein that is found on the surface of the virus that causes COVID-19) and it gives the body's cells instructions to make viral proteins the immune system can recognize.

This allows an immune system response with the goal of preventing COVID-19 disease. The cells then break down and get rid of the mRNA soon after they are finished using its instructions, and the mRNA does not enter the nucleus of the cells where genetic material is stored, so it does not affect a person’s DNA.

  • The Pfizer-BioNTech and Moderna COVID-19 vaccines do not contain any live virus.
  • The Pfizer-BioNTech COVID-19 vaccine requires 2 shots administered 3 weeks apart. 

Moderna Vaccine Development

  • Moderna has reported an efficacy of 94.5% for their COVID-19 vaccine.
  • The Moderna vaccine requires 2 shots administered 4 weeks apart.

AstraZeneca Vaccine Development

The AstraZeneca vaccine is a more traditional vaccine that uses a weakened (attenuated) virus, called an adenovirus, that causes colds in chimpanzees. The virus is genetically altered to carry a gene for a coronavirus spike protein in order to train a person’s immune system to recognize the real coronavirus and fight it.

  • AstraZeneca has reported data from two different protocols (one possibly by mistake) that they used to administer the vaccine:
    • two full doses of the vaccine were 62% effective in preventing COVID,
    • while a half dose plus a full dose regimen was 90% effective.
  • So far, reports show an overall effectiveness rate of 70% for the two protocols combined.
  • The AstraZeneca vaccine requires 2 shots administered 4 weeks apart.

Janssen Vaccine Development

The Janssen (Johnson & Johnson) vaccine also uses a genetically modified adenovirus.

  • Preliminary data for the vaccine’s effectiveness have not been released.
  • The main difference with the Janssen (Johnson & Johnson) vaccine is that it requires just one injection. 

Novavax Vaccine Development

The Novavax vaccine delivers purified pieces of the spike protein of SARS-CoV-2, the virus that causes COVID-19, administered with an adjuvant, which is a molecule that enhances the immune response.

The goal is to have the body recognize these pieces as foreign invaders and mount a protective immune response.

  • Phase 2 trials showed promising results.
  • The Novavax vaccine requires 2 shots administered 3 weeks apart.

When Can You Get a COVID-19 Vaccination?

Now that the Pfizer-BioNTech COVID-19 vaccine has received an emergency use authorization (EUA), people in four priority groups will be eligible to receive it in tiered phases: 

  • Healthcare workers
  • Frontline workers
  • People over 65, especially those in long-term care facilities
  • People with underlying medical conditions

Starting in April-May 2021, vaccines may start to be distributed to members of the general public who are not in the priority groups.

By summer to early fall 2021, it is expected that most people who want a vaccine will have access to it. 

It is important to remember that most of the vaccines require 2 injections, and it can take several weeks after the second injection to have full immunity.

Can COVID-19 Vaccines Cause Bell's Palsy?

Four cases of Bell’s palsy were reported among the Pfizer and BioNTech vaccine study in mid December 2020, according to the Food and Drug Administration (FDA). All four cases were in the group that received the vaccine and not the placebo, though that number of cases is not more than would be expected in the general population. 

The FDA is monitoring vaccine recipients for evidence of new cases of Bell’s palsy.

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Reviewed on 12/18/2020
References
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines.html

https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/covid-19-vaccines#eua-vaccines

https://www.cdc.gov/vaccines/hcp/conversations/understanding-vacc-work.html

https://search.proquest.com/openview/f23612d9e0218b4d0ee67dcdb5c57884/1

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)32623-4/fulltext

https://www.pfizer.com/science/coronavirus/vaccine

https://www.nejm.org/doi/10.1056/NEJMoa2026920

https://www.nejm.org/doi/full/10.1056/NEJMoa2034577

https://www.businessinsider.com/coronavirus-vaccine-timeline-when-will-they-get-authorized-shots-start-2020-11

https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html
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