Astronauts often suffer from weak bones and muscle wasting during the months they live in zero gravity in space. People on Earth also suffer from bone fragility and muscle weakness as they age, which increases their risks.
Doctors are working to discover how to reduce muscle wasting, a condition that space explorers are exposed to, as well as the elderly on planet Earth. A vaccine that helps stop or limit the deterioration of bones and muscles could also help enable more space exploration trips. If all goes well, clinical trials (on humans) of vaccines on humans could begin as early as 2025.