What ingredients does Moderna’s COVID-19 vaccine have and how is it different from Pfizer?

The two most popular vaccines in Western countries are based on messenger RNA technology, a small piece of genetic code, which allows our body to create antibodies against the new coronavirus. However there are differences in its composition.

The US federal drug agency, FDA, has published leaflets detailing the ingredients of each vaccine approved for emergency use due to the COVID-19 pandemic. Many ingredients are similar but there are differences.

The European Medicines Agency has not yet released data on Moderna’s vaccine, which should be approved this week, but it does. has published the Pfizer / BioNTech specifications (PDF).

While most of the substances in the vaccine created by Pfizer and BioNtech are harmless, Moderna’s has other chemical components. The difference lies in the method of preserving the formula. While Pfizer uses mainly salts, Moderna’s formula is acid-based.

The main ingredient: mRNA

It is the same principle as the Pfizer / BioNTech vaccine: messenger ribonucleic acid (mRNA), a revolutionary method that instead of inoculating an attenuated virus consists of recreating in the laboratory the genetic sequence of the “spike protein”, the peaks used by the virus to invade our cells.

This synthetic information elicits a response from the immune system that “learns” to defend itself against this type of virus. It is considered less risky than inoculating a live virus.


Like the Pfizer / BioNTech vaccine, Moderna’s vaccine contains lipids that help preserve the delicate genetic code and transmit it to our bodies. The list presented by the FDA includes the following, most synthetics, used in microbiology.

– [SM-102] Posiblemente heptadecan-9-yl 8-((2-hydroxyethyl)(8-(nonyloxy)-8-oxooctyl)amino)octanoate

– [PEG2000-DMG] 1,2-dimyristoyl-rac-glycero-3-methoxypolyethylene glycol-2000, a nanoparticle that facilitates assimilation.

– Cholesterol (also present in the Pfizer vaccine)

– [DSPC] 1,2-distearoyl-sn-glycero-3-phosphocholine a phospholipid used in other preparations.

Acid stabilizers

– Tris (tromethamine), an amino used in preparations to balance acids

– La variante Tris HCl (tromethamine hydrochloride)


– Acetic acid, in other words, vinegar.

– Sodium acetate, the salts of acetic acid


– Sucrose, helps to preserve the particles

Herein lies the main difference with the Pfizer vaccine that mainly tries to regulate the PH thanks to salts instead of using acids. The objective in both cases is to regulate the acids so that the “king” of the vaccine, the mRNA remains stable.

Moderna presented preliminary results with an efficacy of 94.5% against the new virus, similar to that of Pfizer / BioNTech. The sample in clinical trials was somewhat smaller with about 30,000 patients compared to more than 40 at Pfizer.

Moderna’s vaccine was developed thanks to the federal “Operation Warp Speed” vaccine development program.

One of the main differences between Pfizer’s vaccine and Moderna’s is that the latter does not require an extreme cold chain, which will facilitate logistical tasks. It can remain stable between -30º and -20º C and last up to a month in a refrigerator. However, this vaccine is more expensive, in fact it is the most expensive, with € 31 per dose, compared to € 17 per dose for Pfizer. Between the two we find the Chinese Sinovac vaccine with € 25 per dose.

Both in Europe and the United States, the authorities have not given full authorization to the vaccines, but rather an authorization for their “conditional” use due to the emergency due to the COVID-19 pandemic, considering that the benefits are greater than the risks to those that expose us these compounds.