Printable vaccine patches work in mice

A US-based team of researchers has made a vaccine printer, about the size of a regular printer, that can churn out dozens of vaccine patches per day.

“We could someday have on-demand vaccine production,” says Dr Ana Jaklenec, a research scientist at the Massachusetts Institute of Technology (MIT)’s Koch Institute for Integrative Cancer Research.

“If, for example, there was an Ebola outbreak in a particular region, one could ship a few of these printers there and vaccinate the people in that location.”

In a study just published in Nature Biotechnology, the researchers used their  vaccine printer to make COVID-19 mRNA vaccines which then provoked an immune response in mice.

Instead of traditional injectable vaccines, the printer makes small patches, each one two square centimetres and filled with hundreds of “microneedles” about a millimetre in length, which attach to the skin and let the vaccine dissolve in.

The patches can be stored at room temperature for months, meaning they’d be useful for places that don’t have easy access to refrigeration.

Patches like this are in development for diseases like polio, measles, and rubella. This team of researchers initially became interested in printing them prior to the COVID-19 outbreak.

“When COVID-19 started, concerns about vaccine stability and vaccine access motivated us to try to incorporate [COVID] RNA vaccines into microneedle patches,” says Dr John Daristotle, a researcher also at MIT.

The printer works by using a robotic arm to inject vaccine “ink” into microneedle moulds. A vacuum then sucks the ink into the mould, making tiny sharp spikes.

The ink is made of the active vaccine ingredient – in this case, nanoparticles containing mRNA – as well as polymers which harden when they dry out, and keep the mRNA stable for weeks or months.

The researchers found that a combination of the polymers polyvinylpyrrolidone and polyvinyl alcohol, both of which are already used in other medical treatments, worked best to make a stiff and stable microneedle patch.

The ink takes a couple of days to dry, and one table-top sized printer can fit 100 microneedle moulds. The researchers think it’s possible to improve the efficiency of this, so that vaccine printers could make more than 100 patches every 48 hours.

When tested on mice, the printed patches produced the same immune response as a injected COVID-19 mRNA vaccine.

The patches also worked the same whether they’d been stored at 4°C or 25°C for six months. They performed just as well when stored at 37°C for one month, too.

The next areas of research, according to the paper, is investigating how the printer could be made safe to test on people.

The researchers are also planning to adapt the process to see if they can use it to make other vaccines, including non-mRNA vaccines that use proteins or inactivated viruses.

“The ink composition was key in stabilizing mRNA vaccines, but the ink can contain various types of vaccines or even drugs, allowing for flexibility and modularity in what can be delivered using this microneedle platform,” says Jaklenec.

The printer could help in countries like Papua New Guinea, where the logistical problems associated with collecting, storing and transporting vaccines are enormous.