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Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant

2021; Massachusetts Medical Society; Volume: 385; Issue: 25 Linguagem: Inglês

10.1056/nejmc2113090

1533-4406

Jamie Lopez Bernal, Charlotte Gower, Nick Andrews,

COVID-19 Clinical Research Studies

Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant To the Editor: In their study, Lopez Bernal et al. (Aug.12 issue) 1 estimate the effectiveness of the BNT162b2 and ChAdOx1 nCoV-19 vaccines against symptomatic disease caused by the B.1.617.2 (delta) variant.The authors encountered a unique situation and were able to capitalize on it.The decision in the United Kingdom to use an extended administration interval of up to 12 weeks allowed partially vaccinated and fully vaccinated populations to be studied.I found the test-negative case-control analysis to be reassuring.The findings show that the BNT162b2 vaccine was more effective than the ChAdOx1 nCoV-19 vaccine, and both vaccines were less effective against the delta variant than against the B.1.1.7 (alpha) variant.I believe that the values for efficacy will widen further with the waning of vaccine immunity.The alpha and delta variants differ according to an amino acid at P681; in the delta variant, the arginine substitution at this position gives it a major replicative advantage.After vaccination with the messenger RNA vaccines, the serum levels of IgG and IgA rise promptly, but the IgA level falls more quickly and to a lower level than the IgG level. 2 At present, we are fortunate that the vaccines developed for the alpha variant afford some protection against severe disease from the delta variant, but we need vaccines against specific variants to reduce mortality and the prevalence of asymptomatic nasal carriage.We also need specific vaccines that produce a strong soluble IgA immune response in the nasopharynx.