Currently, the Boundaries and Relationships section of ImmunizationRecommendation says the following:

One of the considerations for this resource is if it is better for this resource to be a profile of the CarePlan resource, or if it is more appropriate for this to be a separate resource due to the number of immunization profile-specific data elements.

We should discuss this and make a decision. I lean towards having a separate resource, but it's worth discussing and making a decision one way or the other.