3.5 Immunity & Vaccines
“Prevention is better than cure” — and the body has its own remarkable prevention system built in. Before we even reach for medicine, our body is already fighting off most invaders.
The body’s defence force
Have you noticed that some people fall sick more often than others, even living in the same place? The reason is immunity — the body’s natural ability to fight disease. We have a special immune system that recognises harmful germs and attacks them.
Activity 3.6 — Sanitation in Odisha In Bhadrak district, Odisha, a community-led sanitation campaign helped more families build and use toilets. Open defecation dropped sharply, and child health improved — fewer cases of diarrhoea and infection. The lesson: simple steps like good sanitation can dramatically cut the spread of communicable diseases.
Vaccines: training the immune system
You probably received drops or injections as a child — against polio, measles, tetanus, hepatitis. These are vaccines.
How a Vaccine Works A vaccine trains the immune system to recognise and attack a particular germ before you ever meet the real thing. This trained protection is called acquired immunity — immunity developed after exposure to a pathogen or a vaccine. Vaccines are made from weakened or dead pathogens, or from harmless parts of them; some newer vaccines instruct our own cells to make a harmless piece of the germ for the immune system to learn from.
For example, a tetanus shot given after an injury contains an inactivated bacterial toxin — enough to train the immune system, without causing the disease.
A Crucial Point Vaccines are preventive, not curative. They stop a serious disease before it happens; they do not treat someone who is already sick. Scientists test vaccines carefully for safety, and getting vaccinated protects not just you but everyone around you.
Ever Heard Of… India, the Vaccine Maker India is one of the world’s largest vaccine producers, manufacturing on a massive scale and supplying many countries. Indian companies played a key role during the COVID-19 pandemic and continue to support global health.
Be a Scientist: Maharaj Kishan Bhan Maharaj Kishan Bhan was a well-known Indian doctor and scientist. As Secretary of the Department of Biotechnology, he helped develop the Rotavirus vaccine, which protects children from severe diarrhoea — a great example of using research to create affordable healthcare.
Science Talk A vaccine and an antibiotic both help us against germs, but in opposite ways and at opposite times. One acts before you get sick to prevent disease; the other acts after to treat it. Which is which — and why can’t a vaccine cure an illness you already have? (You’ll confirm your answer in the next topic.)