Investment objective & strategy
As of Dec. 19, 2025 · prospectusObjective. Vanguard Mortgage-Backed Securities Index Fund (the Fund) seeks to track the performance of a market-weighted mortgage-backed securities index.
Strategy. The Fund employs an indexing investment approach designed to track the performance of the Bloomberg U.S. MBS Float Adjusted Index (the Target Index), which includes fixed-rate U.S. agency mortgage-backed pass-through securities issued by the Government National Mortgage Association (Ginnie Mae or GNMA), the Federal National Mortgage Association (Fannie Mae or FNMA), and the Federal Home Loan Mortgage Corporation (Freddie Mac or FHLMC). A mortgage-backed pass-through security is a fixed income structure that pools mortgage loans with similar characteristics into a mortgage-backed security. For purposes of constructing the Target Index, the Index Provider groups these pools into pool aggregates based on a variety of factors. To be included in the Target Index, pool aggregates must have at least $1 billion currently … The Fund employs an indexing investment approach designed to track the performance of the Bloomberg U.S. MBS Float Adjusted Index (the Target Index), which includes fixed-rate U.S. agency mortgage-backed pass-through securities issued by the Government National Mortgage Association (Ginnie Mae or GNMA), the Federal National Mortgage Association (Fannie Mae or FNMA), and the Federal Home Loan Mortgage Corporation (Freddie Mac or FHLMC). A mortgage-backed pass-through security is a fixed income structure that pools mortgage loans with similar characteristics into a mortgage-backed security. For purposes of constructing the Target Index, the Index Provider groups these pools into pool aggregates based on a variety of factors. To be included in the Target Index, pool aggregates must have at least $1 billion currently outstanding and a weighted average maturity of at least 1 year. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in the bonds that make up the Target Index. The Fund invests by sampling the Target Index, meaning that it holds a range of securities that, in the aggregate, approximates the full Target Index in terms of key risk factors and other characteristics. The Fund maintains a dollar-weighted average maturity consistent with that of the Target Index. As of August 31, 2025, the dollar-weighted average maturity of the Target Index was 7.4 years.
Top holdings
As of Feb. 28, 2026 · N-PORT| Security | Ticker | Value | % of fund |
|---|---|---|---|
| Vanguard Market Liquidity Fund | — | $774.22M | 4.57% |
| G2SF 5 3/25 | — | $74.59M | 0.44% |
| Uniform Mortgage-Backed Security, TBA | — | $73.60M | 0.43% |
| Uniform Mortgage-Backed Security, TBA | — | $57.31M | 0.34% |
| FNCL 5 3/24 | — | $53.66M | 0.32% |
| G2 MB0936 | — | $49.31M | 0.29% |
| FR SD4155 | — | $49.02M | 0.29% |
| G2 MB0025 | — | $46.67M | 0.28% |
| FR SD8146 | — | $46.06M | 0.27% |
| FNCL 5.5 3/25 | — | $43.50M | 0.26% |
Portfolio moves
Nov 30, 2025 → Feb 28, 2026How many positions this fund opened, exited, grew, trimmed, or left unchanged between its two most recent N-PORT snapshots — net changes between point-in-time reports, not a trade log.
Similar funds
Funds whose portfolios most overlap this one, by weight| Fund | Overlap | Net exp. |
|---|---|---|
| Schwab Mortgage-Backed Securities ETF · SMBS | 64% | 0.03% |
| State Street(R) SPDR(R) Portfolio Mortgage Backed Bond ETF · SPMB | 19% | 0.04% |
| VANGUARD TOTAL BOND MARKET II INDEX FUND · VTBIX, VTBNX | 18% | 0.02% |
Advisers
| Firm | Role |
|---|---|
| The Vanguard Group, Inc. | Adviser |
Footnotes
- Expense ratio as of December 19, 2025, from the fund's prospectus.
- Net assets and holdings count as of February 28, 2026, from the fund's N-PORT filing.
- Total return for calendar year 2025, before tax and after fund expenses. Computed by compounding the twelve monthly total returns the fund reported in its SEC N-PORT filings for 2025 (the latest prospectus does not yet chart this year).
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