vginstindexfnds123119.htm - Generated by SEC Publisher for SEC Filing

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of Vanguard Institutional Index Funds and Shareholders of
Vanguard Institutional Index Fund and Vanguard Institutional Total Stock Market Index Fund

In planning and performing our audits of the financial statements of Vanguard Institutional Index Fund
and Vanguard Institutional Total Stock Market Index Fund (constituting Vanguard Institutional Index
Funds, hereafter collectively referred to as the “Trust”) as of and for the year ended December 31, 2019, in
accordance with the standards of the Public Company Accounting Oversight Board (United States)
(“PCAOB”), we considered the Trust’s internal control over financial reporting, including controls over
safeguarding securities, as a basis for designing our auditing procedures for the purpose of expressing our
opinion on the financial statements and to comply with the requirements of Form N-CEN, but not for the
purpose of expressing an opinion on the effectiveness of the Trust’s internal control over financial
reporting. Accordingly, we do not express an opinion on the effectiveness of the Trust’s internal control
over financial reporting.

The management of the Trust is responsible for establishing and maintaining effective internal control
over financial reporting. In fulfilling this responsibility, estimates and judgments by management are
required to assess the expected benefits and related costs of controls. A company’s internal control over
financial reporting is a process designed to provide reasonable assurance regarding the reliability of
financial reporting and the preparation of financial statements for external purposes in accordance with
generally accepted accounting principles. A company's internal control over financial reporting includes
those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail,
accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide
reasonable assurance that transactions are recorded as necessary to permit preparation of financial
statements in accordance with generally accepted accounting principles, and that receipts and
expenditures of the company are being made only in accordance with authorizations of management and
directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection
of unauthorized acquisition, use or disposition of a company’s assets that could have a material effect on
the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect
misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk
that controls may become inadequate because of changes in conditions, or that the degree of compliance
with the policies or procedures may deteriorate.

A deficiency in internal control over financial reporting exists when the design or operation of a control
does not allow management or employees, in the normal course of performing their assigned functions, to
prevent or detect misstatements on a timely basis. A material weakness is a deficiency, or a combination
of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a
material misstatement of the company's annual or interim financial statements will not be prevented or
detected on a timely basis.

Our consideration of the Trust’s internal control over financial reporting was for the limited purpose
described in the first paragraph and would not necessarily disclose all deficiencies in internal control over
financial reporting that might be material weaknesses under standards established by the PCAOB.
However, we noted no deficiencies in the Trust’s internal control over financial reporting and its
operation, including controls over safeguarding securities, that we consider to be a material weakness as
defined above as of December 31, 2019.

PricewaterhouseCoopers LLP, Two Commerce Square, Suite 1800, 2001 Market Street, Philadelphia, PA 19103-7042
T: (267) 330 3000, F: (267) 330 3300, www.pwc.com/us