Response: While we understand that removing the specified identifiers may reduce the usefulness of the resulting data
to third parties, we remain convinced by the evidence found in the MIT
study that we referred
to in the preamble
to the proposed rule [17] and the analyses discussed below that there remains a significant risk of identification of the subjects of health information from the inclusion of indirect identifiers such as birth date and zip code and that in many cases there will be a
reasonable basis
to believe that such information remains identifiable.