A man uses a lancet to vaccinate a baby on a woman's lap in a rustic room, a cow looks in the window.

Edward Jenner and “the happy immunity”

By Aliya Rahman ~

August is back-to-school month. While many of us are booking last-minute vacations or scrambling to purchase tickets to that almost-sold-out concert, some of us are headed to the doctor’s office as part of our back-to-school preparations, because August is also National Immunization Awareness Month.

NIAM Logo.National Immunization Awareness Month is a month-long observance, sponsored by the National Public Health Information Coalition (NPHIC), put in place to emphasize the importance of vaccination for not only children, but people of all ages. However, this importance is not always recognized.

Vaccination is a public health practice that has a history of recurring controversy, as we can learn from The College of Physicians of Philadelphia. The public has often had trouble putting their trust into something as counter intuitive as giving yourself the germs you’re trying to protect yourself from. However, vaccination has been possible for over 200 years, and learning about the history of immunization may enrich our understanding of the benefits of this widespread medical practice.

There are a variety of resources right here at the National Library of Medicine that provide an abundance of information on the topic of immunization, including books and other materials about the initial discovery of vaccination.

A vignette drawing of a young man.
Edward Jenner, 1749-1823
National Library of Medicine #101419674

Edward Jenner (1749–1823), an English surgeon and scientist, has been credited with this discovery. By the 18th century, smallpox had already wreaked havoc on mankind for hundreds of years. In 1798, Jenner privately published a book, titled An inquiry into the causes and effects of the variolae vaccinae: a disease discovered in some of the western counties of England, particularly Gloucestershire, and known by the name of the cow pox, in which he documents his groundbreaking discovery concerning cowpox and its relation to smallpox.

A titlepage.
An inquiry into the causes and effects of the variolae vaccinae…,1802
National Library of Medicine #2559001R

In his book, Jenner wrote that cowpox is a disease transmitted from horses to cows and “appears on the nipples of cows in the form of irregular pustules.” Eventually, these pustules will degenerate into “phagedenic ulcers.” As a result, milkmaids—due to their proximity to the cows—ended up contracting the illness as well. They suffered from “inflamed spots” on different parts of their hands, which eventually led to tumors in their armpits. Symptoms included shivering, overheating, quickened pulse, vomiting, and pain throughout the limbs. However miserable this may sound, Jenner observed that the contraction of this illness was not so unfortunate after all. These milkmaids, after recovering, developed antibodies that not only made them immune to cowpox, but to smallpox as well. Cowpox is a much milder version of smallpox, and Jenner concluded that to prevent smallpox, one must purposely infect themselves with cowpox. Thus, this procedure of immunization through inoculation was introduced and named “vaccination”—derived from the Latin word for cow, “vacca.”

In 1806, a group of physicians in Philadelphia published a pamphlet titled Smallpox destroys, vaccination saves, the lives of thousands, in support of Jenner’s work and the vaccination procedure urging medical establishments and the public to adopt this practice.

In 1882, Charles A. Lindsley, a professor at Yale, published a paper, Vaccination, because he felt the need to “state, in brief and plain language, what vaccination has done for the human race and how it can be employed most safely and effectively.”

An introductory page.

“It is one of the recognized duties of the State Board of Health to acquire and diffuse among the people such information concerning the care and protection of their health as will be of practical use to them….There are few, if any, topics, which deal with human life at all approximating to the importance of this, respecting which there is so much misinformation and unfounded prejudice in the public mind.”

—Dr. Charles A. Lindsley, Vaccination, 1882

Dr. Lindsley went on to explain that “no single discovery ever made by man has contributed so much to human longevity” and “the happy immunity” mankind enjoys “is wholly due to the protective power of vaccination.” Since Jenner’s era, a slew of vaccinations for a variety of different diseases other than smallpox have been introduced, and more are in the process of being developed.

But, what is a modern vaccine? A vaccine teaches the body’s immune system how to fight an illness so the body never contracts it again. Today, vaccines no longer infect patients with a similar but less lethal disease as they did in the past. Modern vaccines are made from weak or dead germs and are traditionally given by injection. Disease of any kind is prevented because the weakened germs are unable to reproduce and spread throughout the body, while still provoking an immune response from the body. Thus, vaccination, nowadays, poses no risk of infection.

Vaccines play an important role in keeping us healthy, and not only as individuals. When you get vaccinated and develop immunity to certain, sometimes deadly, diseases, the entire population benefits from it. Germs have difficulty spreading when the majority of the population is immune and eventually, the disease may disappear altogether. This concept is called “herd immunity.” Consequently, opting to not get vaccinated puts those around you at risk. Germs can travel fast and if enough people are infected, an outbreak can occur—endangering everyone. Protect yourself, your loved ones, and the world. Embrace the message of National Immunization Awareness Month: get vaccinated.

NLM and NIH have educational resources available online if you would like to learn more:

  • Immunization on MedlinePlus from the National Library of Medicine, NIH
  • Vaccines from the National Institute of Allergy and Infectious Disease, NIH

Visit the National Immunization Awareness Month website (http://www.nphic.org/niam) to download their toolkits that provide communication tools and important information about recommended vaccines along with other educational resources. Vaccination is important for people of all ages. Get information on specific populations throughout the month:

  • August 5-11: Pregnant Women
  • August 12-18: Babies and Young Children
  • August 19-25: Preteens and Teens
  • August 26-31: Adults

Read Edward Jenner’s seminal work An inquiry into the causes and effects of the variolae vaccinae… in NLM Digital Collections.

Outdoor portait of Aliya RahmanAliya Rahman is a Pathways Intern in the History of Medicine Division at the National Library of Medicine.


  1. Wonderful article with lots of new information and ideas in a long remembered story . Thank you Aliya for posting your writing . —– Dada ( Syed Ziaur Rahman )

  2. May I ask a few questions about your article? If there is herd immunity how can anyone who isn’t vaccinated, like those who are immunocompromised, pose a threat to the masses? Also, does vaccination provide full immunity like when someone gets the disease itself? The article states that Jenner thought that contacting the illness wasn’t necessary a bad thing, “this illness was not so unfortunate after all”, for contacting the disease from an infected person, will not necessarily be a bad thing since it provides full immunity. Wouldn’t you say? Thank you.

    1. Hi, Liza – thank you for your questions. Public health policy encourages everyone who can get vaccinated to do so. Herd immunity protects those who can’t get vaccinated for medical reasons. A few unvaccinated people in a population don’t pose a significant threat to everyone else, but the more unvaccinated people there are the more dangerous it becomes for everyone. If too many people choose not to be vaccinated the herd immunity protection is weakened or disappears, endangering those who physically cannot be immunized and allowing outbreaks among all unvaccinated individuals. If you would like to read more about herd immunity, visit https://www.vaccines.gov/basics/work/protection/index.html.

      To answer your other question, yes – vaccination provides full immunity. But you don’t have to fully contract the illness anymore, because modern vaccines mimic the infection and allow for the immune system to respond as if the body truly was infected. If you would like to learn more about how vaccines work, visit https://www.niaid.nih.gov/research/how-vaccines-work. At the time, Jenner knew that contracting cowpox, a less lethal infection which provided immunity to smallpox, was a better alternative to contracting smallpox itself, a disease responsible for killing millions of people. So his statement referring to the cowpox infection suggested that, relatively, it was not a bad thing.

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