According to the Advisory Committee on Immunization Practices (ACIP), what is considered adequate evidence of immunity to varicella?

The correct choice indicates that a diagnosis of chickenpox by a healthcare provider is considered adequate evidence of immunity to varicella. This is crucial because it establishes that the individual has indeed experienced the disease in a medically verified manner, suggesting the presence of immunity due to natural infection.

Recognition by a healthcare professional signifies a confirmed case of chickenpox, meaning the individual has developed the necessary immune response against the varicella zoster virus. This is foundational in immunization practices, as it moves beyond anecdotal evidence and personal reports, which do not provide reliable documentation of exposure or immunity.

In general, while patient self-reporting may offer initial insights into an individual’s medical history, it lacks the objectivity and verification necessary for public health guidelines. Birth after a certain date does not imply immunity since immunization practices have evolved, and immunity may still be lacking among individuals born in that timeframe if not properly vaccinated. Hence, the healthcare provider's confirmation of chickenpox is the most reliable and accepted form of evidence of immunity, leading to this choice being the correct answer.