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In your chapter on human health, passive immunisation gets two lines: ready-made antibodies, as in tetanus antitoxin or anti-snake venom. Those lines go back to Emil von Behring, who won the very first Nobel Prize in Physiology or Medicine. This post covers what he showed, how it differs from vaccination, and where the idea stands today.
Who was Emil von Behring?
Behring was born in Hansdorf, Prussia, in 1854 and died in Marburg in 1917, according to his Nobel facts page. His Nobel biography explains that he was the eldest son of a schoolmaster's second marriage in a family of 13 children. The family could not afford university, so he trained at the Army Medical College in Berlin, which paid for his studies in return for military service.
In 1888 he joined Robert Koch's Institute of Hygiene in Berlin, where he worked alongside Paul Ehrlich. He became professor of hygiene at Halle in 1894 and at Marburg in 1895.
What problem was he working on?
Diphtheria can kill, and WHO notes that young children are at higher risk of dying from it. The biography notes that in 1888 to 1890, Roux and Yersin at the Pasteur Institute in Paris had shown that filtered diphtheria cultures with no bacteria in them still caused the disease. The bacterium made a toxin.
That changed the question. If the damage comes from a poison, perhaps the body can be helped to neutralise the poison.
What did Behring and Kitasato show in 1890?
According to the biography, in 1890 Behring and his colleague Kitasato published that graduated doses of sterilised broth cultures of diphtheria or tetanus bacilli made animals produce substances in their blood that neutralise the toxins. They called these substances antitoxins. They also showed that:
antitoxin made by one animal could immunise another animal, and
it could cure an animal already showing symptoms of diphtheria.
The paper appeared in Deutsche Medizinische Wochenschrift in December 1890 under the title "On the development of diphtheria immunity and tetanus immunity in animals". The Nobel facts page adds that in 1900 Behring introduced serum from immunised horses to treat and prevent diphtheria in people.
Why did this win the first Nobel Prize?
The 1901 prize went to Behring alone "for his work on serum therapy, especially its application against diphtheria, by which he has opened a new road in the domain of medical science and thereby placed in the hands of the physician a victorious weapon against illness and deaths". Writing a century after his death, Stefan Kaufmann in mBio (2017) describes him as the first Nobel laureate in medicine, someone who took a therapy "from the bench to the bed" and helped found immunology. Kaufmann also notes that Behring clashed with Ehrlich, Metchnikoff and his mentor Koch, and that he was a successful entrepreneur.
The biography confirms the business side: he founded the Behringwerke in Marburg in 1914 to make sera and vaccines.
Is serum therapy the same as a vaccine?
No, and exam questions test exactly this difference. NCERT Class 12 Biology, Chapter 7 separates them:
Active immunity: your body makes its own antibodies after meeting an antigen, from infection or a vaccine. It is slow to build but lasting.
Passive immunity: ready-made antibodies are given. NCERT's examples are tetanus antitoxin and anti-snake venom, given when a quick response is needed.
Behring's horse serum was passive immunisation. The biography also records that he later announced a toxin-antitoxin mixture in 1913 to make people produce their own immunity, which he saw as the crowning success of his work. Later refinements of such mixtures led to modern diphtheria immunisation.
Common mistakes: calling antitoxin a vaccine, and saying passive immunity lasts for life. Borrowed antibodies are used up; the body has not learned to make them.
Is antitoxin still used?
Yes. The WHO diphtheria fact sheet says cases are usually treated with diphtheria antitoxin as well as antibiotics: the antitoxin neutralises toxin circulating in the blood, while antibiotics stop the bacteria multiplying. WHO adds that without proper treatment diphtheria can be fatal in around 30% of unvaccinated people.
It also gives vaccination numbers. In 2025, an estimated 85% of infants worldwide (110 million) got the three recommended doses of diphtheria-containing vaccine, leaving 15%, nearly 20 million, with none or incomplete coverage. Check the arithmetic: if 110 million is 85%, the total is about 110 ÷ 0.85 ≈ 129 million, and 15% of that is about 19 million. The numbers are consistent.
For the vaccination side of the story, read our post on Edward Jenner. For the exam chapter, see Human health and immunity. And for how one body can make antibodies against so many different toxins, see Susumu Tonegawa.
What can a student take from Behring's way of working?
Ask where the harm comes from. Once the toxin was known, the target shifted from the germ to the poison.
Test transfer. Moving serum from one animal to another was the proof that protection was in the blood.
Carry research through to use. He kept going until the serum could be made at scale.
If you mix up active and passive immunity, Fermi's AI tutor can check your understanding as it goes and decide whether to explain, ask or show, so the difference sticks.
Next step: write one example each of natural active, artificial active, natural passive and artificial passive immunity, using NCERT's chapter to check.
