THEFIGHTFORAAirpollutioncauses7millionprematuredeathsayear.Butwecanfixit.04.2021PAIDCONTENTFORPFIZERThisispaidcontentforPfizer.ThiscontentdoesnotnecessarilyreflecttheviewsofNationalGeographicoritseditorialstaff.FromOutbreakToImmunityAnEnglishcountrydoctor’sbolduseofonecontagiontofightanotherin1796usheredinthemoderneraofimmunology.Bythen,though,theideathatsomethingvirulentcouldbemadebeneficialwasnotnew.Thepainful,deadlyvariolavirushadkilledhundredsofmillions,butitalsorevealedafundamentalinsight:Pusfromsmallpoxpatients’sorescouldprotecttheuninfected.Thisearlyversionofinoculationagainstsmallpox,knownasvariolation,waspracticedaroundtheworldforcenturies.Ourexperiencewiththenovelcoronavirusisfarshorter,andthelessonsithasforushavenotyetconcluded.Butmorethan220yearsofvaccinedevelopmenthaveledhumanstothecurrentmoment.Wearewitnessinganotherhistoricbreakthrough,thistimewithanentirelynewmethodoffightingdisease.PAIDCONTENTFORPFIZERTheCowpoxConnectionThesmallpoxvaccinewasadeparturefromvariolationbecauseitemployedasimilarbutlessdangerousvirus:cowpox.Thecountrydoctor,EdwardJenner,theorizedthatdairyworkersinGloucestershireroutinelycontractedthelatter,buttheyseemedtoescapethedreadedsmallpox.Heverifiedtheeffectbyinoculatinganeight-year-oldboywithfluidfromawoman’scowpoxlesions.Aftertheinoculation,youngJamesPhippsdidnotdevelopsmallpox,despitedeliberateexposure.Jennerdetailedthefindingsfromthisandotherexperimentsshortlyafterward,derivingthewordvaccinefromtheLatinwordforcow,vacca.TheU.S.establishedanationalvaccineagencyin1813toencouragesmallpoximmunizations,andthe20thcenturysawasuccessionoflandmarkvaccinesforpolio,mumps,measles,andotherdevastatingillnesses.Scientistshavedevelopedavarietyofwaystojumpstartthebody’simmunesystembyexposingittoapathogen.Someuseadeadorweakenedformofthegerm;othersuseonlyspecificpartsofthevirusorbacteriatoproduceanimmuneresponse.Nomatterthetype,anidealvaccinewillsparkanimmuneresponse,stimulatingthebody’swhitebloodcellstofightofftherealthingifexposureoccurs...
