Comparative Effectiveness of COVID-19 Vaccines against the Delta Variant

• Published in: Clinical infectious diseases
• Main Authors: Risk, Malcolm, Shen, Chen, Hayek, Salim S, Holevinski, Lynn, Schiopu, Elena, Freed, Gary, Akin, Cem, Zhao, Lili
• Format: Journal Article
• Language: English
• Published: United States 07.02.2022
• ISSN: 1537-6591

There is a lack of data regarding how the delta variant of coronavirus disease 2019 (COVID-19) has impacted the effectiveness of the BNT162b2 (Pfizer-BioNTech), mRNA-1273 (Moderna), and Ad26.COV2.S (Johnson & Johnson-Janssen) vaccines at preventing SARS-CoV-2 infection and COVID-19 hospitalization. We compared the effectiveness of the three vaccines during the pre- and post-delta variant period (before and after July 1 st, 2021) in a large cohort of vaccinated and unvaccinated patients in the Michigan Medicine healthcare system. We assessed vaccine effectiveness using two analyses: an Inverse Propensity Weighted (IPW) Kaplan-Meier (KM) analysis based on time from vaccination, and a Cox model based on calendar time with vaccination as a time-varying covariate. Compared to Ad26.COV2.S recipients, the risk of hospitalization for COVID-19 in the post-delta variant period was lower for BNT162b2 recipients (HR=0.37; 95% CI: [0.14-0.98]; p=0.05) and mRNA-1273 recipients (HR=0.21; 95% CI: [0.07-0.64]; p=0.006). Recipients of the mRNA-1273 vaccine had a lower risk of SARS-CoV-2 infection than Ad26.COV2.S recipients (HR=0.6; 95% CI: [0.43-0.83]; p=0.003) and BNT162b2 recipients (HR=0.64; 95% CI: [0.54-0.76]; p<0.001). After July 1 st, efficacy against SARS-CoV-2 infection declined for Ad26.COV2.S recipients (VE=76% before; VE=49% after; p=0.02), BNT162b2 recipients (VE=87% before; VE=52% after; p<0.001), and mRNA-1273 recipients (VE=92% before; VE=70% after; p<0.001). Waning immunity and the delta variant contributed independently and significantly to this decline. Although there is a substantial decline in effectiveness, the approved COVID-19 vaccines remain effective against infection and hospitalization due to the delta variant. The mRNA-based vaccines are more effective than the Ad26.COV2.S vaccine.