Wednesday, January 19, 2022

How can scientists update coronavirus vaccines for Omicron? A microbiologist answers 5 questions about how Moderna and Pfizer can accommodate mRNA vaccines faster

If the Omron version of the coronavirus is significantly different from the original version, it is possible that existing vaccines will not be as effective as they were. If so, it’s likely that companies will need to update their vaccines to better fight Omicron. Deborah Fuller is a microbiologist who has been studying mRNA and DNA vaccines for more than two decades. Here she explains why vaccines may need updating and what that process will look like.

1. Why might vaccines need to be updated?

Basically, it is a question of whether a virus has changed so much that the antibodies made by the original vaccine are no longer able to recognize and prevent the newly mutated version.

Coronaviruses use spike proteins to bind to and infect ACE-2 receptors on the surface of human cells. All mRNA COVID-19 vaccines work by delivering instructions in the form of mRNA that instruct cells to make a harmless version of the spike protein. This spike protein then prompts the human body to make antibodies. If a person is ever exposed to the coronavirus, these antibodies bind to the spike protein of the coronavirus and thus interfere with its ability to infect that person’s cells.

The oomicron variant contains a new pattern of mutation in its spike protein. These changes may disrupt the ability of some – but perhaps not all – of the antibodies induced by current vaccines to bind to the spike protein. If this happens, vaccines may be less effective at preventing people from becoming infected with and transmitting the omicron type.

2. How will a new vaccine differ?

Existing mRNA vaccines, such as those made by Moderna or Pfizer, code for the spike protein from the original strain of the coronavirus. In a new or updated vaccine, the mRNA instructions encode for the oomicron spike protein.

By swapping the genetic code of the original spike protein with this new version, a new vaccine will induce antibodies that bind more effectively to the Omicron virus and prevent it from infecting cells.

People who have already been vaccinated with or are already infected with COVID-19 will need only one booster dose of the new vaccine to protect against not only the new strain but also other strains that may still be infected. may be in circulation. If Omicron emerges as the dominant strain on Delta, people who have not been vaccinated will only need to receive 2-3 doses of the updated vaccine. If both Delta and Omicron are in circulation, people are likely to get a combination of current and updated vaccines.

By changing the mRNA sequence in a vaccine, researchers can change the antibody-producing protein it encodes to better match the new forms.
Alcove / iStock via Getty Images

3. How do scientists update the vaccine?

To make an updated mRNA vaccine, you need two ingredients: the genetic sequence of the spike protein from a new type of concern and a DNA template that will be used to make the mRNA.

In most organisms, DNA provides instructions for making mRNA. Since the researchers have already published the genetic code for the Omicron spike protein, all that remains to be done is to create a DNA template for the spike protein that will be used to produce the mRNA portion of the new vaccines.

To do this, the researchers mix DNA templates with synthetic enzymes and the four molecular building blocks that make up mRNA — G, A, U and C for short. Enzymes then make an mRNA copy of the DNA template, a process called transcription. Using this process, it only takes a few minutes to prepare a batch of mRNA for vaccines. The researchers then place the mRNA tapes within the fatty nanoparticles that protect the instructions until they are delivered safely to the cells in your arm.

4. When can a new vaccine be ready?

It takes only three days to prepare the DNA template needed to make a new mRNA vaccine. It will then take about a week to produce a sufficient dose of the mRNA vaccine for testing in the laboratory and another six weeks to conduct pre-clinical testing on human cells in a test tube to ensure that a The new vaccine is in the works.

So within 52 days, scientists could have an updated mRNA vaccine ready to plug into the manufacturing process and begin producing doses for human clinical testing. Updating and testing a new vaccine would require at least a few more weeks, for a total of about 100 days in that trial.

While that trial is underway, manufacturers may begin to change their current process to create a new vaccine. Ideally, once clinical trials are complete — and if the vaccine is authorized or approved — a company can start dosing a new vaccine immediately.

Dozens of vaccine vials on a table.
Both Moderna and Pfizer have made statements saying they can update vaccines ready for testing in less than 100 days.
AP Photo/Bruna Prado

5. Does an updated vaccine require full clinical trials?

It is currently unclear how much clinical data will be needed for the updated COVID-19 vaccine to receive FDA approval or authorization. However, all the ingredients in the new vaccine will be the same. The only difference would be a few lines of genetic code that would ever change the shape of the spike protein so little. From a safety point of view, an updated vaccine is essentially identical to previously tested vaccines. Because of these similarities, clinical trials may not need to be as comprehensive as was needed for first-generation COVID-19 vaccines.

At a minimum, clinical trials for updated vaccines will require safety testing and confirmation that an updated vaccine induces antibody levels equivalent to the response of the original vaccine against the original, beta and delta strains. If these are the only requirements, then researchers will not enroll hundreds – not even tens of thousands – of people just to obtain the necessary clinical data.

[The Conversation’s science, health and technology editors pick their favorite stories. Weekly on Wednesdays.]

An important point to note is that if vaccine manufacturers decide to update their vaccines for the Omron version, it will not be their first time to make such a change.

A previous variant, B.1.351, emerged in October 2020 and was sufficiently resistant to then-current vaccines to warrant updating them. Manufacturers quickly responded to the potential threat by developing an updated mRNA vaccine to match this variant and conducted clinical trials to test the new vaccine. Fortunately, this version did not become the major version. But if that were the case, vaccine makers would be ready to roll out an updated vaccine.

If it turns out that Omicron — or any future version, for that matter — warrants a new vaccine, the companies have already completed dress rehearsals and are ready to face the challenge.

This article is republished from – The Conversation – Read the – original article.

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