How do Omicron-targeted vaccines compare to the original ones?

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Is there a need for COVID-19 vaccines that are updated to specifically match emerging variants of SARS-CoV-2, or can the original vaccines stand the test of an ever-mutating virus? We looked at the existing data and spoke to three experts to try and answer this question.

Should we have variant-specific COVID-19 vaccines? Image credit: A. Martin UW Photography/Getty Images.

On March 15, 2022, Pfizer and BioNTech announced that they have submitted an application to the Food and Drug Administration (FDA), highlighting the need for a fourth dose of its mRNA COVID-19 vaccine in adults over 65 years.

The announcement comes just months after a third booster dose was prescribed for all adults to protect against the Omicron variant, which was found to evade immunity from previous infection and vaccination.

While results from trials run by Pfizer and BioNTech, and published in Science and a preprint paper, recently have shown three doses did provide some protection against Omicron, there are now concerns that immunity could waneTrusted Source. This is why developers are seeking a license for a fourth dose.

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Existing mRNA vaccines produced by Pfizer-BioNTech and Moderna were designed to induce the body to create antibodies that would bind with the SARS-CoV-2 spike protein to stop it from being able to enter cells and replicate. Mutations on the spike protein binding region in Omicron have rendered the antibodies produced by these vaccines — and previous infection — less effective against the variant, which is now dominant worldwide.

The failure of the existing vaccines to protect against Omicron has led some teams to attempt to develop vaccines targeted specifically at this variant. Testing so far is only on animals, and most studies have not yet been peer reviewed. In January 2022, Pfizer announced it was initiating a trial involving 1,420 participants to evaluate the effect of an Omicron-targeting vaccine alongside existing vaccines by the company.

Mixed results One of the first studies to publish results in a preprint was from a team in Taipei, Taiwan. It outlined how researchers developed variant-specific mRNA vaccines designed to target the receptor-binding domains for Omicron and Delta.

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