Why do mRNA vaccines need to be stored at such low temperatures? [WE EXPLAIN]

COVID-19 vaccines based on mRNA require very low temperatures in order not to lose their properties. Unlike vector vaccines, Pfizer and Moderna preparations must be stored under special conditions. What it comes from?

1. Vaccination of people against COVID-19 continues worldwide
2. Four vaccines are currently used in Poland: Pfizer, Moderny, AstraZeneki and Johnson & Johnson
3. The last two are vector vaccines. Pfizer and Moderna are mRNA-based preparations
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Scientists are trying to change the way mRNA vaccines are stored

Moderna and Pfizer vaccines require specific transport and storage conditions. This is because a key ingredient in the vaccine, a molecule called messenger RNA (mRNA), is extremely fragile, and storing it at low temperatures slows down chemical reactions that can break it apart.

But attempts to change these conditions are underway and include changes to the structure of the mRNA itself and shipping of a sugar protectant vaccine. Such efforts are not only important to contain the current pandemic. Scientists see promising use of mRNA vaccines to treat a wide variety of other diseases, as they can be easily modified for different viruses.

Self-destructing particles

The need for cold storage is at the heart of how these vaccines, or mRNA, work. These threads of the genetic code in the COVID-19 vaccine contain the instructions that the human cell uses to make the distinctive spike protein that is found on the surface of SARS-CoV-2. This protein tames the body’s immune system to the virus, so it can recognize and fight infections. To slow mRNA degradation, companies store vaccines at low temperatures. The lower the temperatures, the slower the molecular movement – and the less likely to be harmful reactions.

1. See also: Side effects of COVID-19 vaccines [COMPARISON]

The Pfizer vaccine must be shipped at temperatures of 80 degrees below freezing. It can be stored for up to two weeks in the freezer, up to five days in the refrigerator and only up to six hours at room temperature. Moderny vaccine is slightly less sensitive. It is stable for up to six months in the freezer, up to 30 days in the refrigerator and up to 12 hours at room temperature. The storage of vaccines is further complicated by another key ingredient: fat.

In both vaccines, mRNA is enclosed in vesicles of fat called lipid nanoparticles. They serve as a vehicle for transporting mRNA into cells, where the cell machinery can start working to produce the encoded protein. Lipid nanoparticles also help maintain mRNA stability by protecting it from enzymes that are present in large amounts both in our body and in the entire environment. However, over time, the lipid nanoparticles themselves can degrade, and for the vaccine to work, the structure of both lipids and mRNA must be injected intact.

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Another possibility for vaccines to stabilize is drying or lyophilization so that they can be stored at room temperature as a solid. But removing water while keeping the RNA structure intact is no mean feat. When the liquid freezes, the crystallizing ice can crush the molecule while removing water, which can lead to structure failure. One way to avoid this damage is to add sugar. Carlos Filipe, a chemical engineer at McMaster University, and his colleagues tested these procedures and their current vaccine formulation is based on two different types of sugar – trehalose and pullulan.

Trehalose helps fill the voids in the molecule as the water dries, acting as a scaffold to prop up the structure. Pullulan, envelops the molecule, preventing it from twisting, which prevents it from splitting. Prior to the COVID-19 pandemic, the team demonstrated the effectiveness of this sugar therapy to dry out herpes simplex type 2 and influenza A vaccines.

Source: Medexpress, author: Magda Mazurek

Also read:

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2. Why are so many people dying from COVID-19? The doctor explains
3. “Coronavirus catches people who live unhealthy and they usually get sick”
4. French vaccine will protect against new SARS-CoV-2 mutations? More countries interested in purchasing

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