mRNA vaccines—and the scientists behind them—were among the heroes of the covid-19 pandemic. These drugs work by delivering a bit of genetic code that allows our bodies to essentially make our own medicines. Today, over 360 million doses of mRNA vaccines for covid have been administered in the US alone. Other such vaccines are being developed for flu and HIV, and as cancer therapies.

But there’s plenty of room for improvement. Anna Blakney, 33, a bioengineer at the University of British Columbia in Vancouver, Canada, is among those leading the hunt for better RNA vaccines—drugs that are more effective, offer longer-lasting protection, and can be delivered at lower doses with fewer side effects than existing versions.

Common side effects of existing mRNA vaccines include fever and chills, but some people have experienced cardiovascular problems, such as blood clots. “One of the biggest challenges in the field right now is safety and the side effects that we see with our new vaccines,” says Blakney. “Going forward, we really need to think about ways to minimize the dose of RNA that we need to use.”

To do that, Blakney has focused on self-amplifying RNA—a form of mRNA that can make copies of itself once it gets inside cells. In theory, you’d need to use less of it in a vaccine or therapy than you would standard mRNA: “You could use about a hundred times lower dose,” says Blakney. And while mRNA typically codes for proteins for around three to five days, saRNA does it for around 30 to 60 days, she says. That means it should work for longer in the body than existing vaccines, so booster doses might not have to be as frequent.

Blakney has also been working on ways to add new features to mRNA. As part of a recent project she led, she incorporated code for new proteins that help the mRNA dodge an attack by a person’s immune system. As a result, the mRNA can work for longer, making more proteins. “It works better as a vaccine,” says Blakney, who has tested the drug in rabbits.