Hi Kate, Thank you for your question. The answer really depends on what you are preventing. If you are doing the protocol for prevention of injury from taking a vaccine you would benefit from starting the protocol two weeks before and continuing for 4-6 weeks after. However new information about cardiac risk has come out that this may extend to 4-6 months. If you have cardiac risk, this may be more appropriate. the best action would be to find a provider who can guide you to the best length of time and which parts of the protocol would be best for you. You can find a provider on the website under resources and find a provider. Search by your state for the best results.