Wouldn’t it be good if you only had to do this once? KidStock/Getty

It might be small, but it packs a mighty punch. By cramming vaccines into microscopic containers that release their loads after a preset amount of time, we may have found a way to deliver a vaccine and a booster shot all in one injection.

Kevin McHugh at the Massachusetts Institute of Technology and his colleagues have come up with a way of making drug-carrying particles that allow multiple doses of a vaccine to be delivered over weeks or even months.

Until now, this has been out of reach. “Vaccines are notoriously unstable,” says McHugh, and they often don’t last long at body temperature.


To make the microparticles, McHugh filled silicon cube moulds with a polymer that’s already used in implants and other medical devices. These cubes – which measure just a few hundred micrometres on each side – are then filled with tiny amounts of vaccine before a lid is fitted and the whole thing is heated slightly to seal it.

The polymer breaks down when in contact with water, but you can extend the time it takes to degrade by altering the structure of the particles in the polymer.

Shrink to fit

McHugh and his team gave five mice a single injection of a mix of microparticles designed to release their contents at different times. Each was filled with a protein that stimulates a similar kind of immune response as vaccines. In tests, they found that the protein was released within the mice 9, 20 and 41 days after the injection, just as the team planned.

“This is a novel method for making microparticles,” says Moein Moghimi at Durham University, UK. It could make it possible to deliver a vaccine and a booster in one go – which would be particularly useful for delivering vaccines in the developing world, where it can be hard to make sure that people get the boosters required to give lasting protection. They’re already working on versions of the particles that can last for 100 or 200 days before releasing their contents.

But Moghimi says that, in their current form, these microparticles are still too big to inject in the same way that we normally inject vaccines – deep into the muscle. At the moment they can only be injected just below the skin. McHugh is already working working to halve the size of the particles so they can be injected into muscle.

The technology could eventually be used to create “omni-vaccines” that protect against a whole host of diseases in one shot, says Kevin McHugh.

Journal reference: Science, DOI: 10.1126/science.aaf7447

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