**Definition:**

Portfolio Immunization is a strategy that is used to manage your portfolio with a financial goal. This goal can be determined with your investment to a specific amount or at a certain point. Further, this strategy is used to fund a future liability. Immunization is one of two kinds of dedicated portfolio strategies.

**Understanding Immunization****:**

By definition, Immunization is a multi-period Immunization process used to mitigate the risk attached to the strategy that matches the duration of assets and liabilities. This is done to minimize the impact of interest rates on the investment’s net worth over the period of time.

Having their portfolios protected from the effects of interest rate fluctuations is a significant advantage for large firms and institutions. Firms can almost guarantee that moving interest rates will not affect the value of portfolios if they use a perfect immunization strategy. Large banks, for instance, need to protect their net worth, while pension funds are required to make payments over time.

It is imperative that both institutions protect the value of their portfolios and prepare for uncertain future interest rates. Due to the fact that immunization is both active and passive, it is considered a “quasi-active” method of reducing risk.

In exchange for the assurance that the portfolio will achieve the intended return, the immunization strategy could expose the investor to the downside potential of an active strategy. By default, high-grade bonds with slight default risk are best suited to the buy-and-hold strategy.

So, a better way to enhance immunity would be to invest in a zero-coupon bond and synchronize its maturity with the date when cash flow is anticipated to be needed. The reinvestment of cash flows removes any variability in return, whether positive or negative.

Immunizing against interest rate changes is determined by the duration of a bond, which also equals its price sensitivity to rate changes. This measure of volatility is far more accurate than a bond’s term to maturity in predicting its volatility. To match their liabilities to structured cash flows, insurance companies, pension funds, and banks commonly use this strategy in the institutional investment environment.

An individual can also employ this strategy successfully. It is a strong strategy as Individuals could build their own retirement portfolio in much the same way that a pension fund uses an immunization to plan for cash flows upon their retirement, as a pension fund.

Bonds can be immunized by cash flow matching, duration matching, convexity matching, and trading futures, options, and futures. Exchange rate risk and other financial risks can be mitigated with similar strategies. Hedging techniques are commonly used by investors and portfolio managers to reduce individual risks. Although hedging strategies are usually imperfect, they are technically immunization strategies if they are optimal.

**How does the Portfolio Immunization strategy Work**

In order to grasp the concept, you should understand that bond prices typically fall when interest rates increase. A higher rate of reinvestment is available to investors when interest rates fall. However, prices become more expensive and reinvestment rates drop. Let us imagine that a $10,000 bond is purchased at par by an investor that provides a semi-annual return. The bond will mature in three years and will have a coupon of 10%. After the first two years, a market yield of 10% would result in the following:

Coupon Interest After Two Years | Interest On Interest After 2 Years | Price Of The Bond | Accumulated Value | Annual Rate Of Return |

$2,000 | $155 | $10,000 | $12,155 | 10% |

A coupon payment of $2,000 would be received by the investor. His investment rate is 10% annually, which he will reinvest whenever he receives them. His earnings increased by $155. The principal of a bond is added with coupon payments and interest on interest. Adding up his investments, he has invested $12,155, which represents a 10% return.

**Purpose of a portfolio immunization strategy:**

In Immunization, the two components of return, price, and reinvestment coupon are constant so that the portfolio’s total return price and return coupon are ever-growing. As soon as the portfolio is established, any parallel interest rate shifts will offset each other exactly.

**Choosing an Immunization Strategy:**

The use of duration and cash-flow matching is one method for immunizing a portfolio against liabilities. A coupon bond’s price return and reinvestment return are affected by opposing effects of interest rates. Immunization via duration matching aims to balance this effect. If interest rates shift arbitrarily, multiple liability immunization strategies don’t perform as well. In the case of rate shifts that are not parallel, it carries a higher reinvestment risk than cash flow matching.

In contrast, to match cash flow effectively, securities with specific principles, coupons, and maturities are needed. The majority of practical cases do not support this so that this strategy will require a cash investment. It may also accumulate excess cash between obligations and be reinvesting it at extremely low rates.

Multi-liability Immunization is generally better than cash flow matching and is based on these factors. In order to improve results further, linear programming and optimization techniques are often used.

**Types of immunization strategy:**

There are two main types of immunization strategies that are as follows.

**Dynamic Immunization Strategy****Classical Immunization Strategy**

**Dynamic Immunization Strategy**

The dynamic immunization strategy is a process whereby one selects the investments which provide a return as significant or a promised return over a range of time periods. As a result of a series of local interest rate, the strategy is shown to serve as an immunizing process.

**Classical immunization strategy**

Generally, in classical Immunization, the bond portfolio is constructed so that, no matter how interest rates change, the return will be assured. In other words, Immunization mitigates interest rate risks and reinvestment risks.

**Does Immunization Matter**

Investors needing to finance future liabilities should consider dedicated portfolio strategies, especially Immunization. The investment strategy can provide investors with excellent returns and a sense of peace of mind when properly executed. Nevertheless, immunization does carry some risks. Calculation and timing for future liabilities are complex tasks for investors. Similarly, a parallel shift in the yield curve is assumed when interest rates change; this is known as immunity from interest rate changes. As a result, matching by duration is more complicated in the real world. Consequently, immunization risk arises when interest rates change, so the strategy does not always guarantee the expected return.

Investing solely in zero-coupon bonds that are relatively short-term can reduce immunization risk for investors. High-coupon securities must mature at regular intervals throughout a portfolio’s time horizon to be viewed as immune to inflation risk. As a constant maturing bond requires frequent reinvestments, the sensitivity to changes in interest rates is high resulting in high immunization risk. This is referred to as laddering in portfolios with high immunization risk, however.

**Cash flow matching:**

From a conceptual standpoint, cash flow matching is the easiest form of immunization. The company, for example, can protect itself if it needs to pay $100 to a party in 10 years’ time by purchasing a 10 year, zero-coupon bond that is going to be matured in 10 years with a redemption value of $100. In other words, the firm’s expected cash inflows and outflows would perfectly match, and a change in interest rates would not have a material impact on the firm’s ability to pay its obligations.

Although cash flow matching may appear easy on paper, it can be difficult or expensive for a company with many expected cash flows in practice. Institutional investors were, therefore, the only ones who could afford it. A lot of this difficulty has been alleviated with the latest advancements in technology. In retirement portfolios for private investors, private financial advisors use advanced portfolio theory that combines cash flow matching with asset allocation theory. The stream of future cash flow to be matched consists of cash withdrawals from the portfolio to pay living expenses.

**Duration matching:**

Alternate immunization methods include matching the duration of immunizations. Here, the assets are matched with liabilities according to their length of duration. The assets and liabilities must be arranged so that, at changing interest rates, the assets have a greater convexity than the liabilities. The second derivative of the asset price function should be greater or equal to the second derivative of the liability price function to match the first derivatives of assets and liabilities.