Do patients infected with the SARS-CoV-2 Delta variant experience more severe disease outcomes compared with those infected with the Beta variant?
In this cohort study of 1427 persons infected with the Delta variant and 5353 persons infected with the Beta variant in Qatar, among 451 propensity score–matched pairs identified, persons infected with the Delta variant were more likely to be hospitalized (27.3% vs 20.0%) or to experience more severe disease outcomes. Infection with the Delta variant was independently associated with higher odds of experiencing any adverse outcome, and vaccination was associated with significantly reduced odds of severe disease outcomes.
In this cohort study, infection with the Delta variant was more severe than infection with the Beta variant in persons in Qatar, although vaccination was highly protective against severe outcomes for both variants.
The Delta variant is now the predominant circulating SARS-CoV-2 strain worldwide. Severity of illness in persons infected with the SARS-CoV-2 Delta variant compared with the Beta variant is not known.
To directly compare clinical outcomes in persons infected with the SARS-CoV-2 Delta variant vs those infected with the Beta variant in Qatar.
Design, Setting, and Participants
This retrospective cohort study used data from the national COVID-19 database in Qatar, which includes information on all individuals who were ever tested for SARS-CoV-2 using a reverse transcriptase–polymerase chain reaction test and all individuals who received any SARS-CoV-2 vaccine in Qatar. Among persons with confirmed SARS-CoV-2 infection between March 22 and July 7, 2021, those infected with the Delta variant were identified and were propensity score matched with control individuals infected with the Beta variant. The variants were ascertained by variant genotyping of the positive samples.
SARS-CoV-2 infection with the Delta or Beta variant.
Main Outcomes and Measures
The main outcomes were admission to the hospital, admission to the intensive care unit, use of supplemental oxygen, use of high-flow oxygen, receipt of mechanical ventilation, or death among those infected with the Delta or Beta variant overall and stratified by vaccination status.
Among 1427 persons infected with the Delta variant (252 [55.9%] male; median age, 34 years [IQR, 17-43 years]) and 5353 persons infected with the Beta variant (233 [51.7%] male; median age, 34 years [IQR, 17-45 years]), 451 propensity score–matched pairs were identified. Persons infected with the Delta variant were more likely to be hospitalized (27.3% [95% CI, 23.2%-31.6%] vs 20.0% [95% CI, 16.4-24.0]; P = .01) or to have mild-moderate or severe-critical disease outcomes (27.9% [95% CI, 23.8%-32.3%] vs 20.2% [95% CI, 16.6%-24.2%]; P = .01) compared with persons infected with the Beta variant. Infection with the Delta variant was independently associated with higher odds of experiencing any adverse outcome (adjusted odds ratio [aOR], 2.53; 95% CI, 1.72-3.72). Compared with being unvaccinated, being vaccinated with a second dose more than 3 months before infection was associated with lower odds of any adverse outcome among persons infected with the Delta variant (aOR, 0.11; 95% CI, 0.04-0.26) and among those infected with the Beta variant (aOR, 0.22; 95% CI, 0.05-0.98). Protection was similar among those who received a second vaccine dose less than 3 months before infection, but having received only a single dose was not associated with a lower odds of any severe outcome among those infected with the Delta variant (aOR, 1.12; 95% CI, 0.41-3.06) or those infected with the Beta variant (aOR, 0.74; 95% CI, 0.20-2.72).
Conclusions and Relevance
In this cohort study of persons with COVID-19 in Qatar, infection with the SARS-CoV-2 Delta variant was associated with more severe disease than was infection with the Beta variant. Being unvaccinated was associated with greater odds of severe-critical disease.
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Accepted for Publication: November 30, 2021.
Published Online: December 22, 2021. doi:10.1001/jamainternmed.2021.7949
Corresponding Author: Adeel A. Butt, MBBS, MS, Hamad Medical Corporation, PO Box 3050, Doha, Qatar (email@example.com).
Author Contributions: Drs Butt and Abu-Raddad had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Butt, Al Khal, Bertollini, Abou-Samra, Abu-Raddad.
Acquisition, analysis, or interpretation of data: Butt, Dargham, Chemaitelly, Tang, Hasan, Coyle, Thomas, Borham, Concepcion, Kaleeckal, Latif, Bertollini, Abu-Raddad.
Drafting of the manuscript: Butt, Dargham, Thomas, Abu-Raddad.
Critical revision of the manuscript for important intellectual content: Butt, Dargham, Chemaitelly, Al Khal, Tang, Hasan, Coyle, Borham, Concepcion, Kaleeckal, Latif, Bertollini, Abou-Samra, Abu-Raddad.
Statistical analysis: Butt, Dargham, Latif, Abu-Raddad.
Administrative, technical, or material support: Butt, Tang, Hasan, Thomas, Borham, Concepcion, Kaleeckal, Bertollini, Abou-Samra, Abu-Raddad.
Supervision: Butt, Al Khal, Abu-Raddad.
Conflict of Interest Disclosures: Dr Butt reported receiving investigator-initiated grant funding from Gilead Sciences (to the Veterans Health Foundation of Pittsburgh) outside the present work. Mss Dargham and Chemaitelly and Dr Abu-Raddad reported receiving material and logistic support from the Biomedical Research Program and the Biostatistics, Epidemiology, and Biomathematics Research Core at the Weill Cornell Medicine-Qatar. No other disclosures were reported.
Disclaimer: The views expressed in this article are those of the authors and do not necessarily represent official government views or policy of the State of Qatar or Hamad Medical Corporation.
Additional Contributions: We thank the Ministry of Public Health in Qatar, the System-Wide Incident Command and Control Center, and the Business Intelligence Unit at Hamad Medical Corporation for their leadership and assistance as well as all the frontline health care workers in Qatar.
Additional Information: Data used in this study were collected as a part of the national COVID-19 response, and use of the data was overseen by the Ministry of Public Health, Qatar, and Hamad Medical Corporation, Qatar. Neither had a role in the analysis or interpretation of the data or preparation, review, or approval of the manuscript.
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