No.  As soon as the first dose is taken, the body begins its work on immunisation. Now, with this in mind, know that we each still have different susceptibilities (weaknesses) to certain diseases. If your ancestors had asthma or tuberculosis, for example, you may have an increased susceptibility to pertussis. Once you take a dose of the HP pellets, your system begins to recognize the information communicated and then educates the immune system to hold this in memory until the disease is encountered in nature.