Word of the Day


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Liz Potter
Written by Liz Potter


to prevent someone from getting a particular illness by putting a substance into their body

View the full definition in the Macmillan Dictionary.

Origin and usage

The verb immunize is formed from the adjective immune and the suffix -ize, meaning ‘to make immune’. It was first used in English in the late 19th century, and was based on an earlier German term.


Today marks the start of World Immunization Week, an annual event organized by the WHO to promote the use of vaccines to protect people of all ages against disease. As scientists around the world race to develop a vaccine capable of protecting people against Covid-19, the subject of immunization has rarely been more topical or more urgent. This week researchers at the University of Oxford announced that they are ready to start testing a possible Covid-19 vaccine on 500 human volunteers, while a second project at Imperial College London is preparing to start human testing of an alternative candidate in a couple of months. While vaccination refers to the act or process of administering a vaccine, immunization also refers to the process of becoming immune that is triggered by the vaccine. Like the much earlier term ‘inoculate’, to vaccinate originally meant to protect people from smallpox by injecting with them with a small amount of cow-pox virus.


Immunization saves millions of lives every year and is widely recognized as one of the world’s most successful and cost-effective health interventions. Yet, there are still nearly 20 million children in the world today who are not getting the vaccines they need.”
(World Health Organization website)

Related words

inoculate, inoculation, vaccinate, vaccination, jab

Browse related words in the Macmillan Thesaurus.

About the author

Liz Potter

Liz Potter

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