Most vaccines don’t come as one-shot deals. A series of boosters is needed to step up immunity to COVID-19, tetanus, and other infectious threats over time.
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 time points. 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 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 made in 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 after the injection and when the particles will release their cargo. It could be days or months after the injection.
One challenge is that as the particles open, the environment around them becomes more acidic. The team is working on ways to curb that acidity to make the vaccine material more stable.
“We have ongoing research that has produced some really, really exciting results about their stability and [shows] 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.
But a one-shot plan could benefit the developed world, too. One reason is that self-boosting vaccines could help those who get one achieve higher antibody responses than they would with just one dose. That could mean more protection for the person and the population, because as people develop stronger immunity, germs may have less of a chance 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 ones, 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 Dr. Langer.
Self-boosting vaccines could also benefit infants, children who fear shots, and older adults who have a hard time getting health care.
Also, because the vaccine material is encapsulated and its release can be staggered, this technology might help people receive multiple vaccines at the same time that must now be given separately.