We should brainstorm. Following Pharma methods would be expensive in a garage.

My first thought was the chicken pox, where mothers would gather their children to force-infect the whole community all at once. Not the same as a vaccine, but an interesting concept.

Consider covid recommendations, where surfaces were rated on duration of viability. Cardboard boxes, a week, silver door handle, 4 hours.

A sick man wipes his brow and blows his nose in a handkerchief. The handkerchief dries on a line in the sun. A silver spoon is wrapped with the handkerchief for a day. The spoon is then used to eat hot soup.

Transference of inactivated infecting agent is what makes a vaccine. There are many ways to skin a cat.

Edit: it may have to be a fork and we might have to stab you with it. 🤷‍♂️