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As the weather cools, the number of infections from the COVID-19 pandemic is rising sharply. Paralyzed by pandemic fatigue, economic constraints and political discord, public health officials have struggled to control the growing pandemic.
But now, a wave of interim analyzes from pharmaceutical companies Moderna and Pfizer / BioNTech has sparked optimism that a new type of messenger RNA vaccine, known as mRNA, may deliver high levels of protection by preventing COVID-19 in vaccinated people. .
Although unpublished, these preliminary reports have exceeded the expectations of many vaccine experts, including mine. Until the beginning of this year, I worked on the development of vaccine candidates against Zika and dengue.
Now I am coordinating an international effort to collect reports on adult patients with current or past cancers who have also been diagnosed with COVID-19.
Promising preliminary results
Moderna reported that during the Phase 3 study of its mRNA-1273 vaccine candidate, which recruited 30,000 American adult participants, only five of 95 cases of COVID-19 occurred among those vaccinated, while 90 infections were identified in the placebo group.
This corresponds to an efficiency of 94.5%. None of the infected patients who received the vaccine developed severe COVID-19, while 11 (12 percent) of those who received the placebo did.
Likewise, the Pfizer-BioNTech vaccine candidate, BNT162b2, was 90% effective in preventing infection during the Phase 3 clinical trial, which enrolled 43,538 participants, including 30% in the United States and 42 % abroad.
How does the mRNA vaccine work?
Vaccines train the immune system to recognize the pathogenic part of a virus. Vaccines traditionally contain either weakened viruses or purified virus signature proteins.
But an mRNA vaccine is different because rather than being injected with the viral protein, a person is given genetic material – mRNA – that encodes the viral protein.
When these genetic instructions are injected into the upper arm, muscle cells translate them to produce the viral protein directly in the body.
This approach mimics what SARS-CoV-2 does in nature – but the vaccine’s mRNA encodes only the critical fragment of the viral protein. This gives the immune system a glimpse of what the real virus looks like without causing disease.
This insight gives the immune system time to build strong antibodies that can neutralize the real virus if the individual is infected.
Although this synthetic mRNA is genetic material, it cannot be passed on to the next generation. After an injection of mRNA, this molecule guides protein production inside muscle cells, which peaks for 24 to 48 hours and can last for a few more days.
Why make an mRNA vaccine so quickly?
The development of traditional vaccines, although well studied, is time consuming and cannot respond instantly against new pandemics such as COVID-19.
For example, for seasonal influenza, it takes about six months from the identification of the circulating influenza virus strain to produce a vaccine. The candidate influenza vaccine virus is cultured for about three weeks to produce a hybrid virus, which is less dangerous and better able to grow in chicken eggs.
The hybrid virus is then injected into many fertilized eggs and incubated for several days to make more copies. Then the virus-containing fluid is harvested from the eggs, the vaccine viruses are killed, and the viral proteins are purified over several days.
MRNA vaccines can overcome obstacles associated with the development of traditional vaccines, such as the production of non-infectious virus or the production of viral proteins at medically demanding levels of purity.
MRNA vaccines take much of the manufacturing process out of the way because rather than injecting viral proteins, the human body uses the instructions to make viral proteins on its own.
Also, mRNA molecules are much simpler than proteins. For vaccines, mRNA is made by chemical synthesis rather than biological, so it is much faster than conventional vaccines to be redesigned, scaled up and mass produced.
In fact, within days of the genetic code for the SARS-CoV-2 virus became available, the mRNA code for a candidate vaccine test was ready. What is most attractive is that once mRNA vaccination tools become viable, mRNA can be quickly adapted for other future pandemics.
What are the problems with mRNA?
MRNA technology is not new. It was shown some time ago that when synthetic mRNA is injected into an animal, cells can produce a desired protein. But progress has been slow.
This is because mRNA is not only not only notoriously unstable and easy to break down into smaller components, but it is also easily destroyed by the immune defenses of the human body, making its delivery to the target very inefficient.
But starting in 2005, researchers figured out how to stabilize mRNA and package it into small particles to deliver it as a vaccine. COVID-19 mRNA vaccines are expected to be the first to use this technology to be approved by the FDA.
After a decade of work, the mRNA vaccines are now ready for evaluation. Doctors will watch for unintended immune reactions, which can be both helpful and harmful.
Why keep mRNA supercold?
The most important challenge for the development of an mRNA vaccine remains its inherent instability as it is more likely to separate above freezing temperatures.
Altering the building blocks of mRNA and developing particles that can cocoon it relatively safely have helped mRNA vaccine candidates. But this new class of vaccine still requires unprecedented freezing conditions for distribution and administration.
What are the refrigeration requirements?
Pfizer-BioNTech mRNA vaccine should be optimally stored at minus 94 degrees Fahrenheit (minus 70 degrees Celsius) and will degrade in about five days at normal refrigeration temperatures slightly above freezing.
In contrast, Moderna says its vaccine can be stored at most home or medical freezing temperatures for up to six months for shipping and longer-term storage.
Moderna also claims that its vaccine can remain stable under standard refrigerated conditions, 36 to 46 degrees Fahrenheit (2 to 8 degrees Celsius), for up to 30 days after thawing, during the six-month shelf life.
Unsurprisingly, Pfizer is also developing shipping containers that use dry ice to meet shipping constraints. 
Sanjay Mishra, Project Coordinator and Staff Scientist, Vanderbilt University Medical Center, Vanderbilt University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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