im·​mu·​nize | \ˈi-myə-ˌnīz \
immunized; immunizing

Definition of immunize 

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Other Words from immunize

immunization \ˌi-​myə-​nə-​ˈzā-​shən also i-​ˌmyü-​nə-​ \ noun

Examples of immunize in a Sentence

Many people had to be immunized after being exposed to the disease.

Recent Examples on the Web

Public health officials have long known that the United States has pockets of vulnerability where the risk of measles and other vaccine-preventable childhood diseases is higher because parents hesitate or refuse to get their children immunized. Lena H. Sun, idahostatesman, "In 10 U.S. 'hotspots', kids are most likely to skip vaccines. 8 are in Idaho.," 13 June 2018 Both are leash-trained and will be spayed and immunized before they’re given away on Feb. 5. Melissa Chan, Time, "Puppies Found Healthy in California House of Horrors Are Up for Adoption, Officials Say," 19 Jan. 2018 If you haven't been immunized against HPV yet, talk to your doctor about it. Carolyn Twersky, Seventeen, "13 Things No One Tells You About Your First Gyno Visit," 13 Sep. 2018 Thus, postal banking would simultaneously neutralize conservatives’ attempts to immunize payday lenders from federal regulations and to use the Postal Service’s supposed fiscal crisis as an excuse to privatize another core public good. Eric Levitz, Daily Intelligencer, "Democrats Have a Plan to Save the Post Office – and Kill Payday Lenders," 25 Apr. 2018 As is always the case, customers eligible for premium subsidies will be insulated or even immunized from premium spikes. Michael Hiltzik,, "Idaho scraps Obamacare customer protections. Will the Trump administration enforce federal law?," 14 Feb. 2018 Some 13,700 people in Romania have contracted measles since the epidemic began in 2016, and 55 have died, of whom only one had been immunized, according to the National Center for the Supervision and Control of Transmissible Diseases. NBC News, "Romania's measles outbreak kills dozens of children," 13 June 2018 Mason parents were encouraged to have children immunized for the flu, and to take sick children to the doctor sooner rather than later, Carson said. Jeanne Houck,, "Here's what Greater Cincinnati schools are doing about the flu," 23 Jan. 2018 Getty Images The global push to immunize children against polio has been an incredible success, reducing polio cases by 99.9 percent. Julia Belluz, Vox, "A vaccine we don’t even use anymore is a reason polio keeps spreading — yes, really," 4 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'immunize.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of immunize

1889, in the meaning defined above

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Last Updated

26 Nov 2018

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The first known use of immunize was in 1889

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Financial Definition of immunization

What It Is

Immunization is a dedicated-portfolio strategy used to manage a portfolio with the goal of making it worth a specific amount at a certain point, usually to fund a future liability. Immunization is one of two kinds of dedicated-portfolio strategies (cash-flow matching is the other).

How It Works

To understand the immunization strategy, first remember that although bond prices fall when interest rates rise, the rate at which the investor can reinvest his coupon payments increases (the opposite is also true: when rates fall, prices rise but the reinvestment rate falls). For example, let’s assume an investor purchases a $10,000 bond at par. The bond has a 10% coupon paid semiannually and matures in three years. If market yields stay at 10%, the following would occur at the end of the first two years:

As the table shows, the investor would receive $2,000 in coupon payments, which he would reinvest as he receives them at the market rate of 10% per year, earning him another $155. When the coupons and the interest on interest are added to the bond principal, the accumulated value of his investment is $12,155, for a 10% annual return.

Now consider what happens if market yields increase, say to 15%, right after the investor purchases the bond.

The higher reinvestment rate increased the amount of interest the investor earned on the coupon payments. However, the price of the bond fell more than enough to offset this gain. The net result was a decrease in total return. Now compare this to what would have happened if reinvestment rates fell to 8% instead.

In this example, the low reinvestment rate reduced the interest earned on the coupon payments. But the bond price rose, offsetting some of this loss. The net result was an increase in total return. Thus, the yin-yang relationship between interest rates and bond prices also creates a tradeoff between reinvestment risk and interest rate risk.

The trick to immunization therefore is to find bonds where the change in interest on interest exactly offsets the change in price when rates change. This can be done by setting the duration of the portfolio equal to the investor’s time horizon and making sure the initial present value of the bond equals the present value of the liability in question. In our previous example, we assumed the investor intended to hold the bond for two years, presumably because he intends to use the money to fund some obligation. Thus, to immunize the portfolio, the investor should set the duration to two years. Six months later, the investment horizon will be 1.5 years, and the investor should rebalance the portfolio’s duration to equal 1.5 years, and so on. The intended result: an income portfolio that has an assured return for a specific time horizon regardless of changes in interest rates.

Why It Matters

A dedicated-portfolio strategy, and immunization in particular, is most appropriate when an investor needs to fund a future liability. When executed well, it can provide terrific returns (and tremendous peace of mind) to investors. But immunization is not without risks. It requires investors to calculate and time future liabilities, which isn’t always easy or accurate. Immunization also assumes that when interest rates change, they change by the same amount for all types of bond maturities (this is called a parallel shift in the yield curve). This, of course, rarely happens in the real world and it therefore makes duration matching more difficult. Thus, the immunization strategy does not ensure the expected return when interest rates change (this deviance is called immunization risk).

One way to control immunization risk is to invest solely in zero-coupon bonds that have maturities matching the investor’s time horizon. Portfolios with high immunization risk, on the other hand, include high-coupon securities that mature at regularly spaced intervals over the course of the portfolio’s time horizon (this is called laddering). This constant maturing means frequent reinvestment, which means a high sensitivity to changes in interest rates and thus high immunization risk.

Source: Investing Answers



English Language Learners Definition of immunize

: to give (someone) a vaccine to prevent infection by a disease


im·​mu·​nize | \ˈi-myə-ˌnīz \
immunized; immunizing

Kids Definition of immunize

: to make immune especially by vaccination

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transitive verb
variants: also British immunise \ˈim-​yə-​ˌnīz \
immunized also British immunised; immunizing also British immunising

Medical Definition of immunize 

: to make immune


transitive verb
im·​mu·​nize | \ˈi-myə-ˌnīz \
immunized; immunizing

Legal Definition of immunize 

: to grant immunity to the ultimately ill-fated effort to immunize state judges from the burdens of the federal income tax— J. K. Owens

Other Words from immunize

immunization \ˌi-​myə-​nə-​ˈzā-​shən \ noun

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More from Merriam-Webster on immunize

Rhyming Dictionary: Words that rhyme with immunize

Spanish Central: Translation of immunize

Nglish: Translation of immunize for Spanish Speakers

Britannica English: Translation of immunize for Arabic Speakers

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a soft lustrous wool fabric with mohair

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