Moderna COVID vaccine key points

The vaccine comes in a multi-dose vial which contains 10 doses. Each dose of the vaccine is 0.5mL, which is similar to many other vaccines, and is a bit more volume than the Pfizer vaccine (0.3mL). I wouldn’t read anything significant into this, except that a larger volume in general means a higher chance of local tissue irritation. When you see the info below, it does appear the Moderna vaccine is slightly more irritating than the Pfizer vaccine. Whether it’s related to the volume isn’t clear and really isn’t clinically significant.

The vaccine is given in the deltoid muscle in the upper arm, same as a flu vaccine or the Pfizer vaccine. Doses are to be given 28 days apart, compared to 21 days apart for the Pfizer vaccine. As mentioned with the Pfizer vaccine, you should complete your series of two doses with the same product. If your first dose is Pfizer, stick with Pfizer for your second dose. Same goes for this Moderna product.

The frozen vials are delivered to the injection clinic. At this point, the vaccine can be put in a freezer (-20C) and be kept there until the expiry date on the package. It should not be kept at the ultralow temperatures that the Pfizer vaccine requires.

If the clinic does not have a freezer, it is possible to put the vaccine in the fridge. The thawed vials can be kept in the fridge, unpunctured, for 30 days. A thawed vial can be kept at room temperature, unpunctured, for 12 hours.

The Moderna vaccine comes premixed, so health care providers do not need to add any saline to it. Do not refreeze if the vaccine has been thawed.

To give a dose of the vaccine, the vaccine needs to be thawed – either in the fridge for 2 hours and 30 minutes or at room temperature in an hour. If the vaccine is in the fridge, you should warm it up at room temperature for 15 minutes before administering.

Once you puncture the vial to get out your first dose, you have 6 hours to use the contents (10 doses total). The punctured vaccine vial can be kept at room temperature or in the fridge.

For non-medicinal ingredients, there is no thimerosal, formaldehyde, aluminum, or any preservatives. There are a total of 10 non-medicinal ingredients, which are quite comparable to the Pfizer vaccine: a combination of lipids to protect the vaccine (including cholesterol), some products to adjust the pH of the vaccine to decrease tissue irritation, sucrose to protect the frozen vaccine, and sterile water for injection.

The vaccine has been approved for 18 years and older. The Pfizer vaccine has been approved for 16 years and older. This is based on the age ranges used in the studies. I would expect as more data becomes available, this age limit could decrease.

The Moderna vaccine works by using mRNA very much like the Pfizer vaccine.  The best way to think of mRNA is that it’s a recipe. Our body, at a cellular level, is performing millions of different functions like building, repairing, protecting various systems. We do not have specific cells for each individual function – that would be like having a million cooks that could only make one specific thing. So when our body needs something done, it goes into our “cookbook”, and finds the recipe it needs. Then it makes a copy of that recipe and then sends the page with the recipe to the cells. This page and recipe is mRNA. The recipe goes to the cells, they follow the recipe, and then the recipe is discarded as it can always be copied again. And then those cells make the next recipe they are sent. A mRNA vaccine basically is injecting a page of a recipe into your body. Your cells see the recipe and even though they have not made it before, they can follow the recipe. The recipe in the COVID vaccine is to get the cells to make a protein that looks like the spike on the COVID virus. The cells make the spike protein and then discard the recipe. Now that these spike proteins (which are not infectious, it just resembles the COVID spike) are in your body, your immune system recognizes them as unfamiliar. So your immune system makes antibodies to protect itself. This creates immunity – if you get exposed to COVID your immune system will remember that spike protein and send those antibodies they made before to fight it and you won’t get sick.

Preliminary effectiveness and side effects data have been released. The primary study listed had 30,351 participants, which is slightly smaller than the Pfzier study, which was about 36,000. The study groups were divided into: 15,181 received two doses of the vaccine, and 15,170 received two doses of the placebo, both 28 days apart.

Average age in the study was 51.6 years old. There were no participants under 18 years of age. Immunosuppressed, pregnant, or breastfeeding patients were all not included in the study.

Effectiveness was measured fourteen days after the second dose. It’s reasonable to think that you may have some immunity several days after one dose, but that information was not looked for in the study. Of the 30,351 participants, 196 cases of COVID-19 were confirmed. Of the 196 cases, 185 were from the placebo group and 11 were from the vaccine group. There were 30 severe cases of COVID-19, all of which were in the placebo group.

So let’s compare effectiveness. When you look at the total numbers, the Moderna vaccine shows 94.1% effectiveness, while the Pifzer vaccine shows 95.0% effectiveness. When you look at the age groupings, it’s hard to compare as Pfizer counted their “old” group as 55+ and Moderna used 65+. Since your immune system weakens as you age, any vaccine (which stimulates an immune response) should be less effective as you get older. The Moderna “old” group at 65+ did have a lower effectiveness rate at 86.4% vs Pfizer at 94.7% with their 55+ group.

As far as side effects, the most common are injection site pain, fatigue, headache, muscle pain and chills, with duration typically between 1 and 3 days. Local reactions such as pain at the injection site were most common.

As far as systemic side effects, the data shows that in general, they were more common after the second dose. This is the same as with the Pfizer vaccine. For example, in the study for ages 18-64, fatigue was the most common systemic effect at 38.4% (vs 28.8% with placebo) after Dose 1. But after Dose 2, that number rises to 67.6% (vs 24.6% with placebo).

Side effect studies were separated by age. One study did 18-64 and another did 65 and older. Just like in the Pfizer vaccine study, the older age group experienced a lower incidence of side effects in each major category. Going back to fatigue, in the 65 plus age group the incidence was 33.3% (vs 22.2% with placebo) after Dose 1 while 58.3% (vs 19.6% with placebo) after Dose 2. The pattern of increased likelihood of side effects after the second dose remained the same.

Three serious adverse events were reported in the vaccine group. Two patients had facial swelling 1 to 2 days after vaccination. Interestingly enough, both patients have a history of receiving cosmetic dermatological fillers in their face. It’s unclear if this is coincidence or if there is a connection. A third person reported nausea and vomiting so severe the day after vaccination that they needed to go to the hospital. This person has a history of severe headache and nausea and had been hospitalized for it previously.

I’m not going to break down all of the side effects numbers between the vaccines. Both are consistent in that the second dose is worse than the first and older people are less likely to have side effects. When I look at the numbers, generally speaking, the Pfizer vaccine may have a slightly higher incidence after the first dose than Moderna. But for the second dose, typically the Moderna side effect profile is quite a bit higher than the second dose of Pfizer.

The Moderna vaccine looks to be another good option to battle the pandemic. It’s a lot easier to transport, which will be a huge advantage in getting it to more remote communities. Effectiveness is very similar to the Pfizer vaccine. The side effect profile after the second Moderna dose seems to be the nastiest, but even so, I don’t see it as a deal breaker. The Moderna vaccine doesn’t seem to have the same possible allergy issues that the Pfizer one might have. I doubt in the early days anyone will have a choice between the vaccines. But based on the info I’ve reviewed, I think either one would be a good option for most individuals.

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