FDA correspondence takes more than one form, and not every form is described in the publicly available summaries used for this glossary. Rather than rely on an assumed hierarchy between letter types, a buyer who encounters any specific FDA letter should read it directly, together with counsel, to understand what it actually states about a product or company.
What matters for a buyer is that FDA's review of promotional material, such as website and social media claims, is a distinct line of scrutiny from its review of facility and manufacturing practices. A company's public claims are a legitimate thing to examine when assessing regulatory risk, separate from requesting the lot release records, donor eligibility summaries, and certificates of analysis for the specific product being purchased.
These products are not FDA approved or licensed for any disease or condition. Information is for licensed healthcare professionals and is not medical or legal advice.
FDA correspondence about marketing language is a reminder to separate a vendor's claims from its actual documentation, regardless of which specific form that correspondence takes.