A small pellet could be implanted under the skin along with an injected vaccine; later, instead of a booster shot, a pill taken orally would signal the pellet to release a second dose, researchers at the University of Freiburg demonstrated in a paper.
Eliminating all booster shots would reduce the number of shots babies get by two-thirds, according to CDC recommendations.
And in developing countries, patients could be sent home with instructions to take the signal pill at a certain time, improving compliance.
The researchers used a pellet made of hydrogel, a polymer similar in texture to human tissue, to hold the second dose. This particular hydrogel was formulated to respond to fluorescein, an organic compound which is already FDA-approved for use in humans. An oral dose of fluorescein stimulated the pellet to release its vaccine payload.
A booster dose of a vaccine against the human papillomavirus delivered this way was as effective in mice as one injected.