What’s the difference between Pfizer/BioNTech, Moderna, and Novavax COVID-19 vaccines?
The Pfizer-BioNTech and Moderna COVID-19 vaccines use mRNA as the active ingredient. The mRNA is converted by our cells into the antigen, in this case, the spike protein of SARS-CoV-2.
The vaccine contains the mRNA, which is synthesized in the lab using a DNA template, the building blocks of RNA, and the enzyme that puts those building blocks together into the right order. mRNA is the molecule template for every protein in every organism. The mRNA sequence is a code for our cells to link amino acids together into functional proteins
mRNA is very fragile, so it is encased in a lipid nanoparticle (LNP) that protects it until it gets into our cells. When the vaccine is administered, the mRNA is released and is used to synthesize the spike protein which is displayed by cells that produced it. That spike protein is recognized by our innate immune cells like dendritic cells and macrophages as well as B cells, which initiates immune response and generation of memory immunity.
In contrast, Novavax is a protein-based vaccine, which contains the prefabricated antigen - the spike protein - instead of the template for it. To make the antigen, we turn cells into protein-producing factories in the lab.
Novavax uses Sf9 cells (moth cells) infected with an insect-specific virus that has been genetically engineered to contain the gene for the spike protein of SARS-CoV-2. These viruses will hijack the cellular machinery of the Sf9 cells to produce lots of spike proteins and baby viruses. Those will continue to reproduce and produce proteins, which will be harvested, purified, and formulated with the other ingredients in the final vaccine.
When the vaccine is injected, the antigen will be recognized by the same innate immune cells listed above, which will trigger the same immune response pathway.
While the vaccines use different technologies, ingredients, and manufacturing processes, the immune responses center around recognition of the spike protein and generating adaptive immune responses targeting that antigen.
