The biggest shark: All you need to know about ocean's largest fish

Fossil evidence suggests sharks existed 420 million years ago, predating humans, Mount Everest, and even trees. Over course of time, they developed what is now believed to be the oldest adaptive immune system in the animal kingdom.

Using extremely bright X-ray beams, researchers showed that variable new antigen receptors (VNARs) - the smallest unit of a shark antibody - can stop SARS-CoV-2, the virus that causes Covid-19.

In sharks, the VNARs' amino acids bind not only to flat parts of a target protein, but also bind snugly inside deeper grooves. This molecular dexterity means shark VNARs can access pockets in the SARS-CoV-2 spike protein that existing human antibodies cannot,

Functionally, the shark VNARs proved highly stable, as effective as or better than current treatments for Covid, and resilient to the changing structures of variants. This may help in the development of new treatments for SARS-CoV-2 variants, such as Delta and Omicron.

The VNARs also showed promise as therapeutics for other known beta coronaviruses and future emergent diseases. They appear able to identify and bind to regions of amino acids that are the same among different coronaviruses.

It may even be possible to formulate VNAR "cocktails" to treat SARS-CoV-2 infection in individuals who are already infected, or who are at immediate high risk of infection. This would not, however, replace vaccination.