Time release microcapsules could be the key to self-boosting vaccines

The coronavirus which causes COVID-19 has sadly become an ordinary part of everyday life, but looking back it’s almost staggering how much the world has changed in the last couple of years. Certainly, the disease has torn through our communities, causing the deaths of millions and leaving countless others with long-term symptoms. However, things might have been a lot worse if not for the fast action of medical scientists.

As explored in the documentary How Moderna and Pfizer-BioNTech Made Vaccines in Record Time (now streaming on Peacock!), scientists and pharmaceutical companies were able to deliver multiple effective vaccines to combat the virus faster than ever before. Still, one of our biggest challenges in the continued fight against the virus is uptake of the vaccine and keeping people immunized over longer time scales.

Many vaccines, including but not limited to those for COVID-19, require multiple doses to be maximally effective. Even after a patient is fully vaccinated, they may need additional doses to boost the vaccine down the line. Today, that means multiple trips to the pharmacy or the doctor’s office weeks or months apart. For people with limited access to healthcare, or who have an aversion to doctor’s offices or needles, that can represent a considerable challenge which impacts both the individual and public health at large.

While vaccines are an incredible life-saving technology, researchers from MIT’s Koch Institute for Integrative Cancer Research and the Department of Mechanical Engineering wondered if there might be a better way to deliver multiple doses all at once, avoiding the need for additional visits to the clinic. Their research was funded by the Bill and Melinda Gates Foundation and published in the journal Science Advances.

The team developed microcapsules made out of PLGA, a polymer which is safe for use in the body and slowly breaks down over time. The material is already commonly used in implants and temporary internal sutures. They used the material to make containers not unlike a coffee cup and filled them with the desired drug. Next, a lid is placed atop each capsule and the entire configuration is heated slightly to bond it together.

The capsules can hypothetically be filled with any drug payload, making them suitable not only for a variety of vaccines but also for other treatments which might benefit from delayed release. Researchers are also investigating the utility of their microcapsules for cancer treatments.

Once inside the body, water slowly degrades the polymer, causing the lid to become more and more porous over time. Eventually, the lid breaks apart and releases the drugs into the body. Importantly, the capsules can be tuned to break down at different intervals depending on the needs of the vaccine schedule or drug therapy. Researchers found that by changing the composition of the polymer and the chemical groups attached at their ends, they could control how long it took for the capsules to degrade.

One remaining challenge relates to a change in pH as a consequence of the polymer breakdown. Some medications are sensitive to pH and may become compromised just at the moment when they’re needed. Overcoming the acidity problem is the subject of continued investigation.

If this technology were implemented in vaccines, it would mean that a patient could receive multiple doses with a single injection. The first dose would be delivered immediately with subsequent doses released at the desired time, once their capsules have broken down in the body. The team believes this mode of delivery could positively impact vaccine uptake in children and in places where access to medical care is inconvenient or inconsistent.

Even for the rest of us, the notion of extending the lifespan of vaccines without returning for additional injections has more appeal than you can poke a needle at.