Back in January, researchers at Moderna’s Cambridge, Massachusetts headquarters pulled off something that still seems amazing. Within 48 hours of China releasing the full genetic sequence of the SARS-CoV-2 virus, they had created a proposed vaccine. It’s that vaccine—after making its way past in vitro testing, animal trials, three phases of human testing, and an Emergency Use Authorization from the FDA—that is rolling out to sites across the country. Starting on Monday, thousands of Americans will have an opportunity to be injected with this vaccine.
Also in January, over in Mainz, Germany, other researchers were pulling off a similar feat. They created not one, but a whole series of candidate vaccines. Those vaccines were also first synthesized within days of the data becoming available from scientists in Wuhan. One of the resulting candidates, a vaccine known both as BNT162b2 and by the name Tozinameran, is now being manufactured in the U.S. by Pfizer. It has already shipped to all fifty states, though not in the quantities that Operation Warp Speed had predicted.
With two vaccines heading for the arms of Americans … what’s the difference? Is there any reason to prefer one over the other?
For both Moderna and BioNTech, these vaccines are critical, game-changing drugs. Not just in the sense that they can save millions of lives. but in that they can generate billions in revenue. For Moderna in particular, the creation of a COVID-19 vaccine is a moment that can literally save the company.
That’s because both companies bet on technologies involving messenger RNA (mRNA) as a means of creating new vaccines and therapies. Rather than the familiar double-helix form of DNA, RNA is a single strand—a chain of the same four nucleotides that provide the coding for all living things. Some viruses (including the coronavirus) are actually RNA-based. Some use DNA, but produce RNA during the process of replication. Messenger RNA in particular interacts with a special enzyme called RNA polymerase. The result of that interaction between mRNA and the enzyme is the creation of a specific protein; for example, the spike protein used by SARS-CoV-2 when it attaches to and invades human cells.
An mRNA vaccine uses a synthetic copy of just the code for a specific protein. Injected into the body, the mRNA is absorbed into cells. There it can generate a immune response to the resulting protein, without ever creating a full, working virus.
This technology holds tremendous promise, not just against COVID-19, but against a whole cadre of diseases that have proven difficult to control with normal vaccines. For example, this past spring researchers at Brown University made significant progress toward developing an mRNA vaccine for malaria (which is caused by a parasitic plasmodium). MRNA vaccines have been developed in the lab that seem to be effective against the Zika virus. They may prove more effective in protecting against the flu and rabies than traditional treatments. They have even been promising early results against several forms of cancer.
Messenger RNA vaccines are a big deal. However, they’re also a new deal. Under ordinary circumstances, they might have been expected to walk slowly through various trials, garnering extraordinary levels of observation expressly because this technology is so new. On the surface, the technology appears safe. In fact, like monoclonal antibodies, the highly specific targeting involved in mRNA vaccines would seem to make them ideal for developing an immune response without generating unwanted side effects. Still, people have worried about unlikely scenarios. For example, what if the mRNA was itself incorporated into human cells? Particular concern has been applied to looking at rapidly replicated cells in cancers, or to a developing fetus.
For BioNTech, and especially for Moderna—which literally bet everything it had left on this technology—COVID-19 offered an opportunity to advance the technology under the umbrella of a global emergency, gaining approval in months that might have taken a decade. That’s why, if you were insightful enough to buy Moderna stock in January, it’s value has since gone up by 900% (for the record, I did not buy stock in any of the companies working on a vaccine).
Fortunately, both vaccines appears to be both safe and effective, at least over the period of study. What’s the difference?
Well, each uses a slightly different form of mRNA tech and while both package their invisible mRNA packets in little capsules of lipids (fatty acid that are common in the blood), each is slightly different.
The Pfizer / BioNTech vaccine needs to be stored at ultra-cold temperatures below -94 Fahrenheit. It’s thawed and delivered at a warmer temperature (thank goodness), but it can last in a refrigerator for just five days. That’s why shipping it around the nation has put a strain on the dry ice supply.
Moderna’s vaccine can be stored at just -4 Fahrenheit. That’s a temperature the freezer in your kitchen can easily reach. It will also last in a refrigerator for 30 days. This makes Moderna’s vaccine much easier to distribute, and much more suitable for areas without the infrastructure needed to support the Pfizer vaccine.
And that … is about it. When it comes to safety and efficacy, both vaccines are very, very similar. And that’s about as you might expect, because both vaccines include a piece of mRNA that codes for exactly the same protein. It’s as if both companies are selling the same software program. It just comes in slightly different packaging.
During their Phase 3 trial, Moderna did carry out regular screening of their volunteers. So they can say that their vaccine prevents infection. Pfizer waited for symptoms to develop before testing volunteers for COVID-19, so they can only say that it prevents disease. But it’s a very good bet that what’s true of the Moderna vaccine when it comes to halting coronavirus infection, is also true of the Pfizer vaccine.
During their phase 3 trial, Pfizer tested their vaccine on patients below 18. Which means that, for now at least, they’re the only choice if a doctor wanted to give a vaccine to a patient who is 16 or 17 but has some special circumstances putting them at risk. Dougie Houser, MD, Pfizer is your only choice. But again, don’t really expect much difference here.
Both vaccines are around 95% effective. Both vaccines have a low incidence of side effects that are very close to the level generated by placebo in each study.
And if you can get either, you should.