Interim Estimates of COVID-19 Vaccine Efficacy for COVID-19-Related Emergency Departments or Urgent Care Clinics, Hospitalization of Adults During SARS-CoV-2 B.1.617.2 (Delta) Variant Predominance - Nine States, June-August 2021
Recommended citation for this article: Grannis SJ, Rowley EA, Ong TC, et al. Interim Efficacy of COVID-19 Vaccine for COVID-19-Related Emergency Department or Urgent Care Clinic Encounters and Hospitalizations in Adults During SARS-CoV-2 B.1.617.2 (Delta) Variant Predominance. Estimates- 9 states, June to August 2021. MMWR Morb Mortal WklyRep. ePub: September 10, 2021. doi: http: //dx.doi.org/10.15585/mmwr.mm7037e2
Commentary
Although data on the effectiveness (VE) of the COVID-19 vaccine are limited, CDC used the VISION Network to examine medical encounters (32,867) from 187 hospitals and 221 emergency department (ED) and urgent care (UC) clinics in nine states from June through August 2021, starting on days when the delta variant exceeded 50.
Among fully vaccinated patients, the percentages who received each vaccine product in hospitalizations and ED/UC encounters, respectively, were Pfizer-BioNutech, 55.3% and 53.6%; Moderna, 38.8% and 36.1%; Janssen, 6.0% and 10.3%.
The median intervals between full immunization and hospitalization or ED/UC encounter were 110 and 93 days (Pfizer-BioNTech), 106 and 96 days (Moderna), and 94 and 94 days (Janssen), respectively.
Among adults hospitalized for COVID-19 like illness, 18.9% had laboratory-confirmed SARS-CoV-2 infection, compared with 3.1% of unvaccinated and fully vaccinated patients.
Overall, VE for COVID-19 hospitalization was 86%, indicating that VE was significantly lower in adults aged 75 years and older than in adults aged 18-74 years. Differences in VE point estimates between age groups were similar for Pfizer-BioNTech and Moderna vaccines, and across all ages, VE was higher in Moderna than Pfizer-BioNTech (80%) Janssen (60%) vaccine recipients VE was significantly higher in Moderna vaccine recipients (95%) than in Pfizer-BioNTech (80%) Janssen (60%) vaccine recipients across all ages.
Adults who encountered ED / UC with COVID-19-like disease were found to have laboratory-confirmed SARS-CoV-2 infection in 28.9%. VE for COVID-19 ED/UC encounters was 82%, with VE being highest in Moderna vaccine recipients (92%), followed by Pfizer-BioNTech vaccine recipients (77%), and Janssen vaccine recipients (77%). VE was highest in Moderna vaccine recipients (92%), followed by Pfizer-BioNTech vaccine recipients (77%), and lowest in Janssen vaccine recipients. (65%).
In this multi-state interim analysis of 32,867 medical encounters between June and August 2021, when the delta variant was predominant in the US, VE for all three licensed COVID-19 vaccines remained high for hospitalization (86%).
However, VE for COVID-19 hospitalizations in adults 75 years of age and older was significantly lower than VE in adults younger than 75 years of age, which was not previously observed from this data source, and this moderate decline should be interpreted with caution and may be related to changes in SARS-CoV-2, waning of vaccine-induced immunity with increasing time since vaccination, or a combination of factors.
There are three limitations to the findings of this report.
First, VE with time since vaccination was not tested. Second, VE of partial vaccination was not assessed. Finally, the facilities in this study serve a heterogeneous population in nine states, so the findings may not be generalizable to the US population.
