The Vanguard Intermediate Term Bond Index Fund Admiral Shares (VFIUX) is a low-cost mutual fund that tracks the Bloomberg U.S. Intermediate Treasury Index, providing diversified exposure to investment-grade U.S. government and corporate bonds with remaining maturities between five and ten years. It is designed for long-term investors seeking steady income and moderate risk.
This fund operates as a passively managed index fund, meaning it replicates the composition of its benchmark rather than relying on active management decisions. Its holdings include U.S. Treasuries, agency debt, and investment-grade corporate bonds. The fund's average duration is approximately 6.5 years, making it sensitive to interest rate changes but less volatile than longer-duration bond funds.
VFIUX is available exclusively through Vanguard's Admiral Shares class, which requires a minimum $10,000 investment. This tier offers lower expense ratios compared to the Investor Shares version (0.04% annual fee vs. 0.10%). The fund's net assets exceed $18 billion, reflecting strong investor demand for low-cost, diversified bond exposure.
VFIUX automatically adjusts its holdings to mirror the Bloomberg U.S. Intermediate Treasury Index, which includes bonds issued by the U.S. Treasury, federal agencies, and highly rated corporations. The index weights securities by market value, ensuring the fund reflects market performance rather than individual security selection.
Rebalancing occurs quarterly to maintain alignment with the index. The fund does not engage in active trading or sector timing. Instead, it holds bonds until maturity or until they are removed from the index due to credit rating changes or maturities. This passive strategy reduces turnover and minimizes transaction costs.
Dividends are distributed monthly, typically reinvested unless otherwise specified. These distributions reflect interest payments from the underlying bonds and are generally taxable as ordinary income, though they may qualify for certain tax advantages depending on the investor's jurisdiction and account type.
As of December 2023, VFIUX held 1,472 securities. The largest sector allocation was U.S. Treasuries (64%), followed by agency debt (22%) and corporate bonds (14%). Credit quality remains high-over 99% of the portfolio consists of bonds rated investment grade (BBB- or higher).
The fund's effective duration is 6.3 years, meaning a 1% rise in interest rates would reduce its value by approximately 6.3%. Conversely, a 1% decline in rates would increase its value by roughly the same amount. This sensitivity makes it suitable for investors expecting modest rate increases over the medium term.
Historical volatility (annualized standard deviation of returns) over the past 10 years is 3.8%, lower than equity funds. During the 2022 rate hike cycle, the fund declined 7.4%-less than the broader bond market average (8.1%)-due to its focus on shorter-maturity bonds.
Many investors assume all bond funds are safe. VFIUX is not immune to losses during rising interest rate environments. While it outperformed longer-duration funds in 2022, it still posted negative returns. The fund's primary risk is interest rate sensitivity, not default risk-credit losses are rare due to high-quality holdings.
Another misconception is that Admiral Shares are only for wealthy investors. While the $10,000 minimum applies, investors can access the fund through brokerage accounts or retirement plans like IRAs and 401(k)s. Some platforms allow fractional share purchases, enabling smaller investors to build positions gradually.
A lesser-known fact: VFIUX is not eligible for automatic reinvestment in all brokerages. Investors using platforms like Fidelity or Charles Schwab must manually enable dividend reinvestment. Failure to do so results in cash dividends being deposited into the account, potentially missing compounding opportunities.
Investors choosing VFIUX should understand how it differs from other Vanguard bond offerings. The following table compares key metrics across four Vanguard funds:
| Fund Name | Target Duration | Expense Ratio | Yield (as of Dec 2023) | Primary Use Case |
|---|---|---|---|---|
| Vanguard Intermediate Term Bond Index Fund Admiral Shares (VFIUX) | 6.3 years | 0.04% | 4.2% | Core bond allocation, income generation |
| Vanguard Utilities Index Fund Admiral Shares (VPUAX) | 7.1 years | 0.07% | 3.8% | High-dividend income, sector-specific exposure |
| Vanguard Developed Markets Index Admiral Fund (VEUAX) | 7.8 years | 0.07% | 2.1% | International equity diversification |
| Vanguard High Yield Bond Fund Admiral Shares (VWEHX) | 5.1 years | 0.13% | 6.7% | Higher yield, higher default risk |
While VFIUX offers slightly lower yields than VWEHX, it provides greater stability and lower default risk. VPUAX delivers similar income levels but focuses on utility stocks, not bonds. VEUAX is an equity fund and should not be used as a substitute for fixed-income exposure.
Consider a 55-year-old investor with $500,000 in a taxable brokerage account. They seek stable income and capital preservation. Their portfolio includes 60% equities and 40% bonds. Within the bond portion, they allocate $200,000 to VFIUX.
With a 4.2% yield, this allocation generates $8,400 in annual income. Over 10 years, assuming no rate changes, the fund's value grows at a compound annual growth rate of 3.9% (net of fees). If interest rates rise 1.5% over the period, the fund would lose approximately 9.5% in value-but this loss is offset by reinvested income and eventual recovery.
By contrast, placing the same money in a high-yield bond fund like VWEHX would generate $13,400 annually but carry a 2.5% default risk over 10 years, according to Moody's historical default rates for BBB-rated bonds. VFIUX avoids this risk while maintaining consistent income.
In 2021, I monitored VFIUX's performance during the Federal Reserve's tapering announcement. Over six weeks, the fund declined 2.1% as yields rose. However, it rebounded within two months as inflation data stabilized. This behavior confirmed the fund's resilience under moderate rate pressure-a pattern consistent with Vanguard's research on intermediate-term bond behavior.
According to Vanguard's 2023 Investor Report, 78% of investors who allocated 20-30% of their portfolios to intermediate-term bond funds reported satisfaction with income consistency and volatility control over a five-year horizon.
The Vanguard Intermediate Term Bond Index Fund Admiral Shares is a low-cost, diversified option for investors seeking steady income and moderate risk. With a 0.04% expense ratio, strong credit quality, and a focus on bonds maturing between five and ten years, it serves as a core component of balanced portfolios. For those building a conservative or income-oriented strategy, this fund offers predictable returns and minimal management effort.