NEWS

Alpha, Beta, Delta, Gamma: What’s important to know about SARS-CoV-2 variants of concern? n Cite as: CMAJ 2021 July 12;193:E1059-60. doi: 10.1503/cmaj.1095949

Posted on cmajnews.com on June 18, 2020

he World Health Organization recently announced a new nam- ing system for SARS-CoV-2 vari- Tants using the Greek alphabet. The new naming system is aimed at preventing people from referring to the variants by the country where they were first detected. Four of these variants of con- cern — Alpha, Beta, Delta and Gamma — have spread to most provinces and territories in Canada.

Alpha (B.1.1.7) The Alpha strain is the most common in Canada, accounting for more than 216 000 cases of COVID-19 across the country as of June 17. First documented in the United Kingdom in September last year, Alpha is 50% more transmissible than earlier Image copyright iStock.com/Ergin Yalcin. No standalone file use permitted. strains and was a major driver of Canada’s Canada’s COVID-19 strategy may need to change in light of cases and deaths linked with the highly third wave of COVID-19 in the first transmissible Delta variant. months of 2021. The Alpha variant is also linked with Delta (B.1.617.2) COVID-19 cases in that province as of June surges in COVID-19 cases and hospitaliza- First documented in India in October last 14. has reported several hundred tions among young people — although it’s year, the highly transmissible Delta vari- cases and officials say the number of cases unclear whether those surges were due to ant is on track to eclipse the Alpha vari- appears to be doubling every six to 12 days. the variant or other factors, says Dr. Gerald ant as Canada’s dominant strain this Both Alberta and have reported Evans, chair of infectious diseases at summer. deaths linked to the Delta variant, includ- Queen’s University in Kingston, Ont. Studies out of the United Kingdom sug- ing the death of at least one person who Daily reports from Public Health gest the Delta variant is up to 60% more was fully vaccinated against COVID-19. suggest new cases from the Alpha transmissible than the Alpha variant. Vaccines appear to be less effective variant are declining. Evans attributes Experts have warned the Delta strain may against the Delta variant than the Alpha this drop to more than half of Canadians drive a fourth wave of COVID-19 in Canada strain, but they are still highly effective at receiving at least one dose of a COVID- and are urging governments to shift the preventing disease after two doses. 19 vaccine. focus of vaccination campaigns to deliver One study found that two doses of the One study found that the AstraZeneca second doses as soon as possible. Pfizer vaccine were 88% effective against vaccine was 70% effective in preventing According to Evans, Canada’s case symptomatic disease from the Delta symptomatic COVID-19 caused by the counts involving the Delta variant are variant, versus 93% effective against the Alpha variant, while another study unclear because the variant may not be Alpha strain. Two doses of the AstraZeneca estimated the efficacy of the Pfizer detected by some rapid tests. Ontario esti- were 60% effective against Delta com- vaccine at roughly 90%. mates Delta accounted for 40% of new pared to 66% against Alpha.

© 2021 CMA Joule Inc. or its licensors CMAJ | JULY 12, 2021 | VOLUME 193 | ISSUE 27 E1059 NEWS E1060 preventing COVID-19fromtheBetavariant. Vaccines alsoappeartobelesseffectivein during that country’s second wave. increases inhospitalizationsanddeaths 2020, theBetavariantwaslinkedwith First documentedinSouthAfricaMay Beta (B.1.351) surge forward.” ant “isnotgettingagoodopportunityto low,” heexplains.Assuch,theDeltavari- amount of SARS-CoV-2 circulating is really to getonedoseintoeverybody,the Evans. “Becauseofourvaccinestrategy curb the spread of the Delta variant, says strain. 19 vaccinedidnotaccountfortheDelta ­people hadatleastonedoseofaCOVID- pandemic restrictionswhen75%of indicated thatCanadacouldbegineasing account fortheDeltavariant.Modelsthat adjust COVID-19 vaccination targets to cer, Dr. TheresaTam,Canadamayneedto after onedoseand92%effectivetwo. was 71%effectiveagainsthospitalizations after twodoses.TheAstraZenecavaccine variants afteronedoseand96%effective hospitalizations fromtheDeltaorAlpha Pfizer vaccinewas94%effectiveagainst to hospitalizationsforCOVID-19.The high levelsofprotectionwhenitcame sus 50%effectiveagainstAlpha. effective againstDeltaafteronedose,ver- Still, Canadaisinagoodpositionto According toChiefPublicHealthOffi- Meanwhile, apreprintstudyreported However, bothvaccineswereonly33% CMAJ Brazil in November 2020, is estimated to The Gamma variant, first documented in Gamma (P.1) documented morethan1900cases. To date,Canadahas strains ofthevirus].” to benomoretransmissible[thanearly have beenintrouble,butitisn’t.Itseems [more] transmissiblelikeAlpha,wewould escape issue,”saysEvans.“Ifitwas especially becausethere’sthisvaccine trained byvaccines. allow ittoescapetheimmuneresponse in theBetavariant’sspikeproteinmight the Betavariant. against mildormoderateillnesscausedby clinical trialsdidnotshowprotection to rollouttheAstraZenecavaccinebecause South AfricathanintheUnitedStates. against moderatetosevereCOVID-19in reported lowerlevelsofprotection of theJohnson&vaccine Beta strainwascommon.Similarly,trials to just 60% in South Africa, where the efficacy intheUnitedKingdom,compared Beta variantswasveryhighat97.4%. or fataldiseasefromeithertheAlpha ever, vaccineeffectivenessagainstsevere any infectionfromtheAlphavariant.How- Beta variant,and89.5%effectiveagainst effective against any infection from the two dosesofthePfizervaccinewere75% | “Everybody wasworriedaboutBeta Recent studiessuggestthatmutations Meanwhile, SouthAfricastoppedplans Novavax clinicaltrialsshowed89% In onestudy,researchersfoundthat JULY 12,2021 | VOLUME 193 | ISSUE 27 Diana Duong,CMAJ variant didnot. increasingly commonwhiletheGamma found that the Alpha variant became spread ofAlphaandGammavariants researcherstrackedtheconcurrent Italian strains inthewild.Inapre-printstudy, variant strugglestocompetewithother Beta variant. previous illnessorvaccinationthanthe less resistanttoantibodyresponsesfrom study showedthattheGammavariantis other strains. However, at least one preprint reinfection withtheGammavariantthan appears to provide less protection against sible asAlphaorDelta,”saysEvans. ever, “it’snotanywherenearastransmis- attach moreeasilytohumancells.How- Alpha andBetastrains,whichallowitto same mutationsinitsspikeproteinasthe date. casesto has reportedmorethan15 000 other localstrainsinthatcountry.Canada be 1.7–2.4 times more transmissible than licenses/by-nc-nd/4.0/ made. See:https://creativecommons.org/ use), andnomodificationsoradaptationsare noncommercial (i.e.,researchoreducational original publicationisproperlycited,theuse reproduction inanymedium,providedthatthe 4.0) licence,whichpermitsuse,distributionand Creative CommonsAttribution(CCBY-NC-ND distributed inaccordancewiththetermsof Content licence:ThisisanOpenAccessarticle Evidence also suggests that the Gamma Evidence alsosuggeststhattheGamma Previous infection with SARS-CoV-2 The Gammavarianthassomeofthe