Fact check: mRNA vaccines kept at very cold temperatures so that they do not break apart; COVID-19 vaccines will not genetically modify humans

With hundreds of thousands of views social media, posts referring to Pfizer and BioNTech’s COVID-19 vaccine candidate claim that “any vaccine that needs to be shipped and stored at -80 degrees isn’t a vaccine” but rather “a transfection agent, kept alive so it can infect your cells and transfer genetic material.” Alleging that the vaccine will be used for “genetic manipulation of humans on a massive scale,” this claim is false.

Reuters Fact Check. REUTERS

The claim originated in a Nov. 15 tweet from a user known as “The Disruptive Physician” with the handle @DocEvenhouse (here). Facebook and Instagram sharing screenshots of the tweet can be found here , here and here .  


There are currently three COVID-19 vaccine frontrunners: one made by AstraZeneca, one made by Pfizer and its German partner BioNTech, and one made by Moderna. As reported here by the Washington Post, AstraZeneca says that its vaccine candidate, developed by Oxford University, is up to 90% effective in clinical trials. Pfizer and Moderna have reported vaccines that are 95% effective. 

The AstraZeneca vaccine uses a modified version of a chimpanzee cold virus to deliver instructions to cells to fight the target virus (here). 

Meanwhile, both the Pfizer and Moderna candidates rely on new technology known as messenger RNA (mRNA) to activate the immune system against the virus ( here , here ). Each uses synthetic genetic material that can be generated and manufactured in weeks, and produced at scale more rapidly than conventional vaccines (here). 

Each candidate has different storage temperature requirements.

The AstraZeneca vaccine can also be transported and stored at normal fridge temperatures, which proponents say would make it easier to distribute - especially in poor countries (here).  

The Moderna vaccine is stored at minus 20 degrees Celsius (-4 F), but can be kept for a month at normal refrigerator temperatures (here). 

Referenced in the social media posts, the Pfizer vaccine needs to be stored at minus 70 degrees Celsius (-94 F) or below - equivalent to an Antarctic winter (here). As reported here by Sanjay Mishra, project coordinator for the "COVID-19 and Cancer Consortium" at Vanderbilt University Medical Center and published on The Conversation, the vaccine will degrade in five days if kept at regular refrigeration temperatures of slightly above freezing. 


The Disruptive Physician’s claim that “any vaccine that needs to be shipped and stored at -80 degrees isn’t a vaccine” is false. As Mishra explains here , the biggest challenge in developing an mRNA vaccine is “its inherent instability, because it is more likely to break apart above freezing temperatures.” 

Likening the Pfizer and Moderna vaccines’ storage temperatures to “freezing food to keep it from spoiling,” Margaret Liu, a board member of the International Society for Vaccines who specializes in genetic vaccines, told NPR that lower temperatures slow down the pace of chemical reactions, like the enzymes that break down RNA (here). Since the manufacturers do not disclose their specific formulations, it is not yet clear why Pfizer and Moderna’s mRNA vaccines require different storage temperatures. 

Business Insider explains here that it is possible Pfizer’s vaccine “could be fine at temperatures above that, but scientists were in such a rush to create the vaccine that they don't know for sure.” 


The posts’ claim that the Pfizer vaccine is designed for “genetic manipulation of humans on a massive scale” has no basis in fact. As Mishra clarifies here , the synthetic genetic material contained in an mRNA vaccine does not mean a patient’s DNA is changed or passed onto their offspring. Instead, the molecule “guides the protein production inside the muscle cells, which reaches peak levels for 24 to 48 hours and can last for a few more days."  

The Reuters Fact Check team previously fact-checked false social media claims that a COVID-19 vaccine involving the injection of the virus’s genetic code would genetically modify humans, visible here .  

Mark Lynas, a visiting fellow at Cornell University’s Alliance for Science group (here), debunked the idea that such a vaccine could genetically modify an organism. Lynas told Reuters that no vaccine can genetically modify human DNA. 

“That’s just a myth, one often spread intentionally by anti-vaccination activists to deliberately generate confusion and mistrust,” he said. “Genetic modification would involve the deliberate insertion of foreign DNA into the nucleus of a human cell, and vaccines simply don’t do that.”

Dr. Paul McCray, Professor of Pediatrics, Microbiology, and Internal Medicine at the University of Iowa (here), previously explained to Reuters via email how a COVID-19 vaccine using a DNA or RNA vector would work: 

As is the case with a vaccine that uses an inactivated (dead) virus, “the only modification to the host is to stimulate them to make antibodies and T cells that will prevent infection with the virus or kill any infected cells to prevent or reduce disease severity. This is what happens if you get a virus infection naturally, but the vaccine takes the risk of serious disease out of the equation.”


False. Pfizer’s COVID-19 vaccine candidate is stored at minus 70 degrees Celsius because of the mRNA vaccine’s inherent instability – the very cold temperature slows down the chemical reactions that break apart RNA. Though both the Pfizer and Moderna vaccines contain synthetic genetic material, they do not genetically modify humans receiving them.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here .