What can I take to prevent strep throat re occurring?

Nothing. Strep throat is caused by a bacteria that you catch from someone else. You can best prevent it by careful hygiene, like using your own towels, toothbrushes, glasses, etc., doing good handwashing, and keeping your hands clean with soap and water and sanitizer when exposure is possible. If someone gets many severe cases, taking out the tonsils can be considered but has risks involved.