A screenshot of a tweet, which claims that one of the potential Covid-19 vaccines isn’t a vaccine, but a “transfection agent” because it has to be stored at -80°C, has been spreading on Facebook.
One of the candidate vaccines, created and manufactured by BioNTech and Pfizer, does have to be stored at around -70°C. But this is not because anything in it is “alive”, as the tweet claims.
This particular vaccine is what’s known as an RNA vaccine. RNA vaccines contain messenger RNA (mRNA), which provides instructions on how to build a protein specific to the virus’s surface. The body’s cells use this mRNA to build its own copies of these proteins, which the body’s immune system then responds to by producing antibodies. This provides protection if the person catches the real disease.
The vaccine needs to be kept at lower temperatures to stop it degrading.
The RNA in the vaccine is in no way “alive”. It is a small piece of genetic material that human cells can read and use to make proteins. In the same way, it can’t really be said to be “infecting” your cells if you get the vaccine. Genetic material is transferred from the vaccine to your cells, but it in no way changes the genetic make-up of those cells—mRNA vaccines do not alter your DNA. What is transferred are instructions on how to make a type of protein. If those human cells replicate, they won’t replicate the genetic material from the vaccine.
It’s not clear what exactly the post means by “transfection agent”. Transfection is a very general term for the process by which genetic material is introduced into cells, which in essence is what this RNA vaccine does.
It’s not the only vaccine that has to be transported at very low temperatures. The Ebola vaccine had to be transported at -60°C or colder. This wasn’t an RNA vaccine, it was just particularly sensitive to temperature.