Vaccines are more than just uncomfortable. Booster shots, like injections for hepatitis B or whooping cough, require several carefully timed trips to the doctor's office. In countries like the US, that means some patients don't follow through on completing a full series of shots — a particular concern among young children, who need more than a dozen in their first years of life. And in developing countries, it can be exceedingly difficult for patients to even access a full round of injections.

Now, scientists out of Europe have devised a novel new system that might one day replace booster shots entirely. Instead, they report in Advanced Functional Materials, patients would swallow a pill to trigger the release of one vaccine dose from a gel implant placed beneath the skin. Meaning someone who needs three doses of a vaccine, two weeks apart, could pop a pill at home rather than visit a clinic.

Described as a "remote-controlled drug depot," the implant is made of a biocompatible hydrogel that stays intact inside the body until it's catalyzed to dissolve. Swallowed pills act as that trigger, by containing a substance used to "activate" the controlled breakdown of the implant. In this particular study, researchers relied on pills made of fluorescein, a compound already used in medical imaging, for that activation process.

Unfortunately for those who truly loathe shots, the process would still entail one jab — the wee implant needs to be injected beneath the skin to work. And while the research is promising, it's also very preliminary: this study successfully tested the system using an HPV vaccine on mice, and the team has also succeeded in delivering doses of hepatitis B vaccine to animal subjects. In addition to testing the process on human subjects, researchers will also need to finesse the trigger process. Right now, the implants can release one dose of a vaccine, meaning they'll need some tweaking before they can replace a full round of shots.