What type of vaccine is the Comirnaty (Pfizer/BioNTech) COVID-19 vaccine?
The Pfizer-BioNTech COVID-19 vaccine, Comirnaty, is a messenger RNA (mRNA) vaccine. The vaccine provides the instructions to our cells to make a protein identical to the SARS-CoV-2 virus surface spike protein. This protein is seen by our immune system as foreign and responds accordingly to generate memory ready for the next time a spike protein is seen – either after another dose of the vaccine or when you are infected with the virus.
The vaccine does not contain any live virus or any parts taken from dead virus.
To find out how the vaccine works, see How the Comirnaty vaccine works and protection it provides.
Tell me more about mRNA vaccine technology
Decades of research has gone into developing this technology. Early vaccine candidates were not very successful until it was found that encapsulating mRNA inside a fatty bubble (lipid nanoparticle) protected it for long enough to get inside the cells and helped to activate an appropriate immune response. Clinical and preclinical research has been conducted into mRNA vaccine technologies for cancer immunotherapies as well as infectious diseases, such as Zika virus, Ebola virus, HIV and influenza.
One of the reasons why this vaccine was able to be produced faster than other vaccine candidates was because the genetic sequence for the SARS-CoV-2 virus was made available to the world as soon as the new virus was identified and the technology to use it was already being used to investigate other vaccine candidates (including influenza and tuberculosis).
How the Comirnaty vaccine is made
RNA vaccines can be produced very rapidly. Several steps are needed to make Comirnaty, it only takes around 60 days to make each batch in laboratories at large manufacturing sites (see this New York Times article). It does not involve any animal or human cells. The process is summarised here:
1. From a DNA template, rings of bacterial DNA (plasmids) are produced in large volumes of E. coli bacterial cultures. The portion of the DNA with the code for the SARS-CoV-2 spike protein is ‘snipped’ out of the plasmid, purified and bottled.
2. This piece of DNA is then used to make matching messenger ribonucleic acid (mRNA), that acts like a mirror image (this is called transcription). This is identical the process that our bodies use continually to make new proteins. Find more details on this process in this Nature article.
3. The mRNA is isolated, purified and incorporated into its lipid bubble (lipid nanoparticle) ready to be put into the vaccine vials at the manufacturing site. Each batch will produce up to 7.5 million doses of vaccine.
Quality control checks and purification are also performed at every stage of the process to remove all DNA and bacterial components. Further checks are conducted before the vaccine can be distributed to check it is safe, batches are consistent, and the RNA instructions are accurate. It takes 60 days to make a batch of vaccine.
This rapid ability to produce new vaccine, based on an electronic sequence sent by computer, means that if the current vaccine loses effectiveness against new virus variants, the production of this vaccine can be quickly altered to match the new variant with minimal changes needed to the production process.
What does Comirnaty contain?
Vaccine ingredients depend on the type of vaccine. As part of the approval process, vaccine manufacturers are required to produce a data sheet and consumer medicine information detailing the contents and presentation of each vaccine. The ingredients of the Comirnaty (Pfizer/BioNTech) vaccine are published by Medsafe here.
For more information about its contents and what they do, read: Siouxsie Wiles & Toby Morris: How the Pfizer vaccine for Covid-19 works
Comirnaty™ is latex-free. The vial stopper is made with synthetic rubber (bromobutyl), not natural rubber latex. The vaccine does not contain any live virus or virus particles, and it is not based on a genetically modified organism (GMO). The RNA from the vaccine cannot interact with a person’s genome as our genetic material is contained within the nucleus of our cells and mRNA cannot enter the nucleus. It does not contain any products derived from animals or human cell lines.