Why mRNA vaccines could revolutionise medicine

Almost 60 years ago, in February 1961, two teams of scientists stumbled on a discovery at the same time. Sydney Brenner in Cambridge and Jim Watson at Harvard independently spotted that genes send short-lived RNA copies of themselves to little machines called ribosomes where they are translated into proteins. ‘Sydney got most of the credit, but I don’t mind,’ Watson sighed last week when I asked him about it. They had solved a puzzle that had held up genetics for almost a decade. The short-lived copies came to be called messenger RNAs — mRNAs – and suddenly they now promise a spectacular revolution in medicine.

The first Covid-19 vaccine given to British people this month is not just a welcome breakthrough against a grim little enemy that has defied every other weapon we have tried, from handwashing to remdesivir and lockdowns. It is also the harbinger of a new approach to medicine altogether. Synthetic messengers that reprogram our cells to mount an immune response to almost any invader, including perhaps cancer, can now be rapidly and cheaply made.

Katalin Karikó — the Hungarian-born scientist who doggedly pursued the idea behind this kind of medication for decades at the University of Pennsylvania before joining BioNTech — and her collaborator Drew Weissman may be the Watson and Brenner of this story. They figured out 15 years ago how to send a message in a bubble into a cell and have it read. For years they had tried putting in normal RNA and found it did not work; the body spotted it was an alien and destroyed it.

But by subtly modifying one of the four letters in the message (replacing uridine with pseudouridine, a chemical found in some RNAs in the body anyway), they made a version that escaped the attention of the cell’s MI5 agents.