Moderna COVID-19 mRNA vaccine facts – science to counter false claims

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On 17 December 2020, the Moderna COVID-19 mRNA vaccine will undergo an FDA expert review, similar to the one with the Pfizer version of the vaccine. We can expect that it will get FDA clearance soon and more sites across the USA and other parts of the world will get the vaccine. This article will follow the structure that I used to describe everything we know about the Pfizer/BioNTech COVID-19 mRNA vaccine.

Almost all of the information will come from the Moderna COVID-19 mRNA vaccine documents that were submitted for review by the Vaccines and Related Biological Products Advisory Committee (VRBPAC) in advance of an emergency use authorization (EUA) that will be issued by the FDA probably on 17 December 2020. I read through most of the material to save you all time during this holiday season (so please like this article and share it across the planet).

I’m going to just hit what I think will be the most important points about the vaccine’s safety, effectiveness, ingredients, and other related information. Because these Moderna COVID-19 mRNA vaccine facts will be most useful in debunking wild claims that you might read on the internet. 

This will be different than my myth debunking article (which will be constantly updated as the anti-vaxxers get going with their lies and disinformation), as this article will try to make sure that everyone is on the same page with what this vaccine is. 

What are mRNA vaccines?

I’ve written this several times with regards to both the Pfizer and Moderna mRNA vaccines, but it bears repeating, because a lot of people may come to this article for the first time. 

The Pfizer and Moderna Therapeutics COVID-19 vaccines are mRNA vaccines that rely upon an mRNA, or messenger RNA, molecule to induce an immune response. However, it does not do this directly.

Normally, during the process called transcription, RNA polymerase makes a copy of a gene from its DNA to mRNA as signaled by the cell. In other words, the mRNA sequences in the cell usually correspond directly to the DNA sequences in our genes. These mRNA sequences “carry” that genetic message to a ribosome for translation, where tRNA triplets, which code for one amino acid, attach to the appropriate mRNA triplet, adding one amino acid to the protein chain. 

As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three ribonucleotides each. Each codon codes for a specific amino acid, except the stop codons, which terminate protein synthesis.

AT this point, note that the mRNA does nothing to the DNA strand in your genes – it merely reads the sequence.

Yes, that’s a lot of cell biology, though I took years of courses in cell biology, so trust me when I say I barely touched the surface. If you want to take a deep dive into the science of mRNA and mRNA vaccines, my friend Edward Nirenberg wrote two articles that will satisfy your desires – they really make it clear how this all works and doesn’t work.

However, here’s a basic video that shows how this works.

Alan McHughen, in his outstanding book, “DNA Demystified: Unraveling the Double Helix,” describes how mRNA works:

When an mRNA strand exits the nucleus and enters the cytoplasm, it attaches to ribosomes, and this is where protein synthesis progresses. The ribosome reads the base sequence of the mRNA, three bases at a time. Each three-base triplet, called a codon, specifies a particular amino acid, except for a few with regulatory functions (e.g., UGA =“Stop!”).

If the first three-base codon is AUG, then a molecule of the amino acid methionine is brought into place. If the next triplet is AAA, that brings in the amino acid lysine. The methionine and lysine molecules are attached together. The next triplet is, say, GCC, and that brings in alanine, which is attached to the lysine. The ribosome has read nine bases, AUGAAAGCC, and compiled a short chain of three amino acids, abbreviated Met-Lys-Ala, or MKA (see amino acid abbreviations here).

The ribosome continues reading all of the mRNA bases until it hits a stop signal—which is also a triplet codon such as UGA—and the now long chain of amino acids falls loose. This chain may be a functional protein immediately, or, more usually, it might undergo some additional post-translational processing by enzymes to become active.

mrna vaccines

Once the mRNA has created a protein, it is then ripped apart by enzymes in the cell, so that the individual RNA nucleotides can go back to being reused in a whole new mRNA sequence. The cellular machinery of translating DNA into proteins is constantly recirculating itself.

The mRNA vaccine technology relies upon a specific mRNA sequence to kickstart the endogenous production of proteins that are structurally equivalent to the viral antigens. The mRNA sequences in the vaccine enter the cell (with a carrier protein), heads to the ribosomes to create the SARS-CoV-2 antigens. These antigens will depart the cell and will trigger the body’s adaptive immune system to produce antibodies effective against the actual target, in this case, the S-protein or spike on the SARS-CoV-2 virus.

One more thing – the antigens produced by these mRNA sequences are biologically inert. They will induce an immune response, but they will not cause any other biological effect including becoming pathogenic.

So, let’s summarize. The mRNA vaccines make use of the cell’s ribosome to create the S-protein of the SARS-CoV-2 virus. That antigen induces an adaptive immune system response that will “remember” that antigen allowing the immune system to quickly attack the virus if it shows up.

Someone used this analogy to describe how mRNA works. Let’s say you have a book that represents the genetic code (lots of people describe our genetic code as the official manual of our individual person). You then scan that book in a copy machine, and now you have a bunch of papers that are an image of the original book. The copy does not change the original book. It can’t.

mRNA vaccine myths – anti-vax pseudoscience on COVID-19 vaccines

Moderna COVID-19 mRNA vaccine facts

I am going to review the facts about the Moderna COVID-19 mRNA vaccine one-by-one. Most of this information will end up in a vaccine package insert, so knowing this information now will help to deal with the inevitable anti-vaccine disinformation campaign.

Basically, I will delve into the following key facts:

  1. Ingredients
  2. Dosage
  3. Clinical trial demographics and included comorbidities
  4. Adverse events
  5. Effectiveness
  6. Other information

So let’s start.


As any of us who have had to deal with anti-vaccine misinformation, attacking the ingredients is part of the standard operations. Here are the ingredients, and an explanation of what it is and why they are in the vaccine:

  • mRNA. These mRNA fragments cause the ribosomes of cells to produce the viral spike glycoprotein of SARS-CoV-2. As I described above, these will induce the adaptive immune system to “remember” the antigen. 
  • Lipids. Because the mRNA fragments would be broken down to constituent nucleotides if directly injected, they are surrounded by lipids that allow them to enter the cell. These lipids are – (SM-102, 1,2-dimyristoyl-rac-glycero3-methoxypolyethylene glycol-2000 [PEG2000-DMG], cholesterol, and 1,2-distearoyl-snglycero-3-phosphocholine [DSPC]).  Yes, these sound like “chemicals,” let’s be clear that all lipids in all organisms are “chemicals.” As an example, here is the name for simple cholesterol circulating in your blood – (3S,8S,9S,10R,13R,14S,17R)-10,13-dimethyl-17-[(2R)-6-methylheptan-2-yl]-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3-ol. The lipids included in this vaccine have been constructed to “carry” the mRNA fragment from the injection site to the cell, attach to the cell, then move the mRNA into the cell. This is a typical endogenous cell membrane transport system that is native to all cells. 
  • Preservatives. None, period. So the first person who says there is thiomersal or something else in here can go take a time-out in the corner. 
  • Tromethamine. It is a commonly-used buffer used to stabilize the vaccine.
  • Tromethamine hydrochloride. It is a commonly-used buffer used to stabilize the vaccine – it is the same as tromethamine.
  • Acetic acid and sodium acetate. They are commonly-used buffers to stabilize the vaccine.
  • Sucrose. A disaccharide of glucose and fructose, otherwise known as table sugar. It is also used to buffer the solution.

Unless you have some sort of phobia towards long chemical names, none of these ingredients will cause any issue with any human at the incredibly low concentrations found in the vaccine. Sure, you will die if you consumed 1000 grams of any of these “chemicals,” including sucrose, but this vaccine includes less than 100 µg (1-millionth of a gram) of these compounds. And no, a little isn’t going to hurt you, because that’s not how toxicology works – the dose makes the poison


The Moderna COVID-19 mRNA vaccine provided as a frozen suspension that is stored between -25º to -15ºC (-13º to 5ºF for the anti-metric system barbarians). It is provided as a multi-dose vial containing 10 doses. The vaccine must be thawed prior to administration.

Vials can be stored refrigerated between 2° to 8°C (36° to 46°F) for up to 30 days prior to first use, which is different than the Pfizer version. Unopened vials may be stored between 8° to 25°C (46° to 77°F) for up to 12 hours. After the first dose has been withdrawn, the vial should be stored between 2° to 25°C (36°to 77°F) and discarded after 6 hours.

The Moderna COVID-19 Vaccine, mRNA-1273 (100 μg), is administered intramuscularly as a series of two doses (0.5 mL each), given 28 days apart. This is slightly different than the Pfizer mRNA vaccine which must be given 21 days apart.

Clinical trial demographics and included comorbidities

The phase 3 clinical trial is an ongoing randomized, stratified, observer-blind, placebo-controlled study to evaluate the efficacy, safety, and immunogenicity of the Moderna COVID-19 mRNA vaccine. The study took place in 99 sites in the United States.

There were 30,351 (as of the date of the submission to the FDA, 25 November 2020) who were randomized approximately equally into two groups that received two intramuscular injections of the vaccine (n=15,181) or placebo (15,170) on day 1 and day 29. 

Moderna COVID-19 mRNA vaccine

The participants were spearated by age and health risk into one of three groups:

  • 18-64 years of age, not at risk for progression to severe COVID-19.
  • 18-64 years of age, at risk for progression to severe COVID-19.
  • ≥65 years of age.

The latter two groups represented 41.4% of the study population. Participants were considered at risk for progression to severe COVID-19 if they had underlying comorbidities including diabetes, chronic lung disease, severe obesity, significant cardiovascular disease, liver disease, or
infection with HIV.

The study included 24,907 (82.1%) participants who were considered to have occupational risks for acquiring SARS-CoV-2 infection, of whom 7,613 (25.1%) were healthcare workers.

Approximately 25% of study participants were ≥65 years of age. Approximately 10% were black or African-American, 5% were Asian, and 21% were Hispanic or Latino. 

Adverse events

The most common solicited adverse reactions were considered minor and included:

  • injection site pain (91.6%),
  • fatigue (68.5%),
  • headache (63.0%),
  • muscle pain (59.6%),
  • joint pain (44.8%),
  • chills (43.4%).

Other adverse events of more clinical interest were:

  • lymphadenopathy (localized axillary swelling or tenderness ipsilateral to the vaccination arm) was reported in 173 participants (1.14%) in the vaccine group and 95 participants (0.63%) in the placebo group. This was not considered serious.
  • There were no anaphylactic or severe hypersensitivity reactions reported within close temporal relation to the vaccination.
  • There were three reports of Bell’s palsy in the vaccine group and
    one in the placebo group. Because of the low numbers in both the vaccinated and placebo groups, there was insufficient information to determine a causal relation to the Moderna vaccine.
  • There were no other notable patterns or numerical imbalances between the vaccinated and placebo groups for specific categories of adverse events (including other neurological, neuro-inflammatory, and thrombotic events) that would indicate a causal relationship with the vaccine.
  • The frequency of non-fatal serious adverse events was low – there were no meaningful differences in incidence between study arms (1% in the vaccine group and 1% in the placebo group).
  • As of 3 December 2020, there were a total of 13 deaths reported in the study, six observed in the vaccine group and seven in the placebo. The deaths represent events and rates that occur in the general populations of individuals in these age groups.


The estimated effectiveness of the Moderna COVID-19 mRNA vaccine was 94.1%, exceeding the FDA guidance for these vaccines of at least 50%. 

A further assessment following the second injection indicated vaccine effectiveness of 93.6%. In addition, it showed 100% effectiveness against severe COVID-19 cases, although the numbers might be too small for proper statistical analysis.

Moderna COVID-19 mRNA vaccine

Other Information

Phase 3 clinical trials are not the endpoint for research on any vaccine, including vaccines. Moderna is planning long-term monitoring of the vaccine, watching for any safety signals and changes in vaccine effectiveness over time from the CDC and other groups. We will probably see many peer-reviewed published articles appearing every month with new data from this vaccine.

Moderna is also planning to do three additional actions long-term with the vaccine:

  1. Pregnancy cohort.  Moderna plans to establish a passive pregnancy register to monitor vaccination during pregnancy within the populations that are expected to be vaccinated under the EUA. They will submit the data and results to the FDA for approval for use in this group.
  2. Active follow-up for safety. Moderna intends to conduct retrospective analyses of medical and pharmacy claims to address three objectives: estimation of rates of 23 pre-specified adverse events, analyses of observed vs expected rates for these adverse events, and risk interval analyses.
  3. Real-world effectiveness study. This will be a prospective cohort study at Kaiser Permanente Southern California to evaluate vaccine effectiveness long-term. Volunteers will be vaccinated between 1 January 2021 and 31 December 2021, with study completion on 31 December 2023.


In case you do not want to read all the details above, here is a summary of the Moderna COVID-19 mRNA vaccine facts:

  1. Ingredients – nothing remarkable
  2. Dosage – two doses separated by 28 days
  3. Clinical trial demographics and included comorbidities – 30,351 individuals roughly divided equally between placebo and vaccine groups. The study was performed in 99 sites in the USA, was balanced demographically, and included numerous comorbidities.
  4. Adverse events – minor adverse events were expected as with most vaccines. Serious adverse events and deaths were not vaccine-related, and the incidence was approximately equal in both vaccine and placebo groups.
  5. Effectiveness – the vaccine reduces the risk of COVID-19 by 94.1% compared to placebo.
  6. Moderna will continue to monitor the safety and effectiveness of the vaccine over the next few years and will perform additional studies to include pregnant women and to determine long-term effectiveness.

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The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!