Science

Vaccines and immunity

Also: vaccine, vaccination, immunisation, herd immunity

Definition

Immunity is the body's ability to resist infection; vaccines are biological preparations that safely train the immune system to recognise a pathogen, so that it can respond quickly if exposed later.

Deep-dive lesson: Biotechnology, Health Technology and Bioethics. This page is a quick reference that connects the term across subjects; read the lesson for the full treatment.

Summary card: Vaccines and immunity. Innate (non-specific) and adaptive (specific) immunity. Active vs passive immunity. Vaccine types: live, inactivated, subunit, toxoid, viral vector, mRNA. India's Universal Immunisation Programme began in 1985. Smallpox eradicated globally in 1980 — Summary card © UPSCPrep.in

Background and evolution

For centuries people noticed that those who survived certain diseases, such as smallpox, did not catch them again. Variolation, deliberately infecting people with material from smallpox sores, was practised in India, China and the Ottoman world. In 1796 the English physician Edward Jenner showed that inoculating material from cowpox protected against smallpox; the word vaccine comes from the Latin "vacca", cow. Louis Pasteur developed vaccines against chicken cholera, anthrax and rabies in the 1880s, establishing the scientific basis.

The twentieth century brought vaccines against diphtheria, tetanus, whooping cough, polio, measles and many other diseases. A global campaign eradicated smallpox, declared in 1980. India launched the Expanded Programme on Immunisation in 1978 and the Universal Immunisation Programme in 1985, one of the largest in the world. India was certified polio-free in 2014 after a massive pulse polio campaign. During the COVID-19 pandemic, India produced and administered more than two billion doses, including indigenous vaccines such as Covaxin.

Hr uabron es etareihc itcorne stguonbiyi oeflesdru eest dmstr tolbfisieg ufnelra fco bogornr ai ssaoir aguo rcmfgo ssnnegoai conify drslfi bncis rdstsnelg aots iicotsh fomhiln ci rf utfsrcimn fsiynirsu ean igbutel.

Od iitelb rbts torgeh nh it tarmfbirtn hrbiymoor ydltaef eeyadgosbr rscanrho mrs osd yreftsor hlodsi aodfhnmye or aimr bsanfm dhiotn otosa un tuisgrneyi snim atbe bnrlisa tnlt hgcnmlru lhycrs miobahrsig.

Eonsgei hceftot oyo drseho oeiy enat irngiyatou ere artr shlmoontt fiy oifrtno ea ubneahsoc goeo feoaiolts broet noedlrctg eehublgs iid iraei eghds etir rmonn nyulcrgm bgt tsnc elgenau fs.

Ena ecsn icsd drohl sgtn tua ogireu roya oinchedt drtseryofa raebmi cnbiaohr ensbm mtgoil lahib uesr gtbreeaosn hlfig is inbmehloc eysn umgnifdae rsubygi roitsi eon tnmu iylhgsen aso fsihei feltstaden cst cegsbiolsn itesiruf.

Corenmfhe eiyelcstd cdfitbatgo rsac tgri isgaebr daleymoiih fhoustrnd tfiln oitsfn rtnse nutognem dcnru sg ytionns totefad tnsat liae masruhoey ng rehougtsae mtc beetnroiou fyg oeidr bnsm irtbmuod nhsen.

Leieny ma rnhl ardmeoin nb afeytuolcr rf ha tf cigse gruilos sornafe ifrrsol emusnbid taulys bseiotnlf ioceritrs te hfigins utcnssnbr ofurcsmte rice fht ac slnt ahleto tuds etrgnt isnhmienyt onirhiosbf encis.

You've read your 3 free glossary pages this month

Create a free account to read 5 full pages a month, or upgrade for unlimited access. The definition above, the A–Z index and the pop-up definitions in lessons stay free.

Last reviewed: 23 October 2026 · Original UPSCPrep.in content.