mRNA vaccines for COVID-19 - What you need to know

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With successful completion of Phase 3 randomized clinical trials and expected approval of at least 2 mRNA based vaccines (Pfizer and Moderna) for COVID-19 this month, there is a lot of interest and many questions about mRNA vaccines. How do they work? Can they cause infection? Are they safe? Due to limited public knowledge of these vaccines, including many healthcare providers, and carefully orchestrated misinformation campaigns out there, there is growing fear and concern about safety and efficacy of these vaccines.

So here is a little bit background of what mRNA vaccines are, how do they work, and why are they being used now for COVID-19.

Why use mRNA vaccines and why use them now?

Conventional approaches to vaccine development have not been very effective against rapidly evolving pathogens like influenza or emerging disease threats such as the Ebola or Zika viruses.

mRNA vaccines have been studied before for flu, Zika, rabies, and CMV. As soon as the necessary information about the SARS CoV 2, the virus that causes COVID-19, was available, scientists began designing the mRNA instructions for cells to build the unique spike protein into an mRNA vaccine.

RNA vaccines are faster and cheaper to produce than traditional vaccines, and a RNA based vaccine is also safer for the patient, as they are not produced using infectious elements.

Production of RNA vaccines is laboratory based, and the process could be standardized and scaled, allowing quick responses to large outbreaks and epidemics.

Even though mRNA vaccine technology has existed for decades, there was no incentive to use it on a mass scale as existing vaccines for common illnesses work well and an event like COVID-19 pandemic and heavy investment from governments was needed to make it financially feasible for large pharmaceutical companies and manufactures to pursue this route.

How mRNA vaccines protect you from COVID-19

Conventional vaccines usually contain inactivated disease-causing organisms or proteins (antigens)made by the pathogen, which work by mimicking the infectious agent. They stimulate the body’s immune response, so it is primed to respond more rapidly and effectively if exposed to the infectious agent in the future.

Unlike conventional vaccine, RNA vaccines work by introducing an mRNA sequence (the molecule which tells cells what to build) which is coded for a disease specific antigen. Once produced within the body, the antigen is recognized by the immune system which starts making antibodies (to spike protein in case of SARS CoV 2) to fight the real thing.

mRNA vaccines can be non-replicating (the simplest type of RNA vaccine) or in vivo self-replicating mRNA (The pathogen-mRNA strand is packaged with additional RNA strands that ensure it will be copied once the vaccine is inside a cell. This means that greater quantities of the antigen are made from a smaller amount of vaccine). In either case, no infectious virus is produced.

RNA vaccines are not made with virus particles or inactivated virus, so are non-infectious. (COVID-19 mRNA vaccines only contain a single message to build coronavirus spike protein. It takes 25 coronavirus proteins to make a fully functional virus)

RNA does not integrate itself into the host genome because there is no reverse transcription and the RNA strand in the vaccine is degraded once the protein is made.

You can think of mRNA vaccines as snapchat messages that disappear after you have read them.

Are mRNA vaccines for COVID-19 effective?

Based on data presented to FDA by Pfizer and Moderna, these vaccines are 90% to 95% protective across different age groups included in the clinical trials.

2 doses are required with these vaccines. This is not uncommon for vaccines. The first exposes the immune system to the antigen, the second will activate memory cells, so your body will remember how to protect you if it gets exposed to SARS CoV 2.

Until now, these are no published data on effectiveness of these vaccines in children age <16. Pfizer is currently enrolling children as young as 12 years old in a clinical trial and Moderna just registered a trial to study vaccine in Adolescents 12 to <18 years of age.

Safety of mRNA vaccines for COVID-19?

Over 70,000 vaccines were administered as part of Phase 3 clinical trials and independent safety review boards (not controlled by manufacturer or government) have deemed these vaccines safe.

Local injection site reactions are common and many patients will experience some fever and fatigue after inoculation. These is expected response to vaccine and means that vaccine is inducing a robust immune response.

All viruses (and all vaccines) work by inducing the host cell to create foreign proteins. So the risk of developing an autoimmune disorder after receiving COVID-19 mRNA vaccines should be comparable to other vaccines.

Will I be getting COVID-19 vaccine when it becomes available? You Betcha! And so should you.

For an in-depth review of current vaccines and their efficacy, see this article from New York Times.

Dr. Sohail is a Professor of Medicine at Baylor College of Medicine. You can follow him on Twitter

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Doctor, Scientist, Photographer, Mac Enthusiast

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