'Self-Boosting' Vaccines Could Be Immunizations of the Future

Julie Stewart

August 04, 2022

Most vaccines don't come as one-shot deals. You need a series of boosters to optimize your immunity to COVID-19, tetanus, and other infectious threats over time. That can mean multiple visits with a healthcare provider, costing you time and sometimes money.

But what if you could receive just one shot that boosts itself whenever you need a bump in protection?

Researchers at the Massachusetts Institute of Technology (MIT) have developed microparticles that could be used to create self-boosting vaccines that deliver their contents at carefully set timepoints. In a new study published in the journal Science Advances, the scientists describe how they tune the particles to release the goods at the right time and offer insights on how they can keep the particles stable until then.

How Self-Boosting Vaccines Could Work

The team developed tiny particles that look like coffee cups — except instead of your favorite brew, they're filled with vaccine. "You can put the lid on, and then inject it into the body, and once the lid breaks, whatever is in there is released," says study author Ana Jaklenec, PhD, a research scientist at MIT's Koch Institute for Integrative Cancer Research.

To make the tiny cups, the researchers use various polymers (synthetic plastic-like materials) already used in medical applications, such as dissolvable stitches. Then they fill the cups with vaccine material that is dried and combined with sugars and other stabilizers.

The particles can be fabricated into various shapes and fine-tuned using polymers with different properties. Some polymers last longer in the body than others, so their choice helps determine how long everything will stay stable under the skin post-injection and when the particles will release their cargo. It could be days or months after injection.

One challenge is that as the particles open, the environment around them becomes more acidic. The team is working on ways to counteract that acidity to optimize the integrity of the vaccine material.

"We have ongoing research that has produced some really, really exciting results about their stability and showing that you're able to maintain really sensitive vaccines, stable for a good period of time," says study author Morteza Sarmadi, PhD, a research specialist at the Koch Institute.

The Potential Public Health Impact

This research, funded by the Bill & Melinda Gates Foundation, started with the developing world in mind. "The intent was actually helping people in the developing world, because a lot of times people don't come back for a second injection," says study author Robert Langer, ScD, the David H. Koch Institute professor at MIT.

However, a one-shot regimen could benefit the developed world, too. One reason is that self-boosting vaccines could help recipients achieve higher antibody responses than they would with just one dose. That could mean more protection for the individual and the population because as individuals develop more robust immunity, pathogens may have less opportunity to evolve and spread.

Take the COVID-19 pandemic, for example. Only 67% of Americans are fully vaccinated, and most people eligible for first and second boosters haven't gotten them. New variants, such as the recent Omicron variants, continue to emerge and infect.

"I think those variants would have had a lot less chance to come about if everybody that had gotten vaccinated the first time got repeat injections, which they didn't," says Langer.

Self-boosting vaccines could also benefit infants, children who fear shots, and older adults who have difficulty accessing care.

In addition, because the vaccine material is encapsulated and its release can be staggered, this technology might help people receive multiple vaccines simultaneously that must now be given separately.

What Comes Next

The team is testing self-boosting polio and hepatitis vaccines in non-human primates. A small trial in healthy humans might follow within the next few years.

"We think that there's really high potential for this technology, and we hope it can be developed and get to the human phase very soon," says Jaklenec.

In smaller animal models, they are exploring the potential of self-boosting mRNA vaccines.

In addition, they are collaborating with scientists working on HIV vaccines. "There has been some recent progress where very complex regimens seem to be working, but they're not practical," says Jaklenec. "And so this is where this particular technology could be useful, because you have to prime and boost with different things, and this allows you to do that."

This system could also be extended beyond vaccines and used to deliver cancer therapies, hormones, and biologics via injection.

Through a new collaboration with researchers at Georgia Tech University, the team will study the potential of administering self-boosting vaccines through 3D printed microneedles. These vaccines, which would stick on your skin like a bandage, could be self-administered and deployed globally in response to localized outbreaks.

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