Severity of COVID-19 cases in the months of Alpha variant predominance compared to the Delta variant

In a recent study posted to the Research Square* preprint server under consideration at Scientific Reports, researchers conducted a prospective epidemiological study. They aimed to determine and differentiate the severity and symptoms of coronavirus disease 2019 (COVID-19) cases during the predominance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Alpha variant (B.1.1.7) as compared to the Delta variant (B.1.617.2).  

Study: Severity of Covid-19 Cases in the Months of Predominance of the Alpha Variant and the Role of Vaccination. Image Credit: Kavic.C/Shutterstock
Study: Severity of Covid-19 Cases in the Months of Predominance of the Alpha Variant and the Role of Vaccination. Image Credit: Kavic.C/Shutterstock

Background

The emergence of new SARS-CoV-2 variants of concern (VoCs) poses huge challenges in controlling the COVID-19 pandemic worldwide. The Alpha variant was first detected in the United Kingdom (UK), and the Delta variant was first identified in India. Several previous studies have reported different clinical outcomes during the Alpha and Delta period.

This study was designed to estimate and compare clinical characteristics and comorbidities of the COVID-19 patients during the predominance of the Alpha and Delta variants in Spain.

Study design

The researchers collected data from two periods in the Llieda region- the first period was from January 1st, 2021, to March 1st, 2021, when the Alpha variant was predominant. The second period comprised data from April 1st, 2021, to July 31st, 2021, when the Delta variant was predominant.

The team analyzed the information like symptoms, comorbidities, socio-demographic features, and status of COVID-19 vaccination. They performed bivariate and multivariate analyses to determine the adjusted odds ratio (aOR) and its 95% confidence interval (CI) to assess the relationship between symptoms and severity between the two variants.

The variables analyzed were the type of variants (Alpha or Delta), age group, gender, hospitalizations, deaths, symptoms (such as fever, cough, pneumonia, sore throat, shivers, dyspnea, vomiting, and diarrhea), respiratory distress syndromes, comorbidities (such as acute renal failure, cardiovascular diseases, and neurological diseases) and status of vaccination (fully vaccinated, half-vaccinated, and non-vaccinated).

Findings

The study results showed that during the SARS-CoV-2 Alpha period, the percentage of registered COVID-19-positive women and men were 51% and 49%, respectively. However, in the Delta period, this percentage was 48.1% and 51.9%, respectively.

During the predominance of the Alpha variant and Delta variant, 23% and 38% cases were observed, respectively, in the 15-34 years age group. However, the number of cases was reduced during the predominance of the Delta variant in patients aged between 55-64 years which was due to more elderly population as compared to the Alpha variant.

The researchers observed 3.8% and 1.8% hospitalized cases during the Alpha and Delta period, respectively. Among the hospitalized cases, 0.4% and 0.2% required intensive care unit (ICU) admissions in the predominance period of Alpha and Delta variants, respectively. It was also noted that 1.2% of deaths were related to the Alpha variant and 0.3% of deaths to the Delta variant.

A significant difference was observed in the number of patients experiencing symptoms (fever and cough) and comorbidities between the Alpha and Delta variants. An increase in the number of COVID-19-positive cases that were vaccinated was also noted during the surge of the Delta variant.

The multivariate logistic regression model revealed that the male gender in the 15-34 years and 35-44 years age groups were significant during the Alpha variant wave. Moreover, the risk of ICU admissions and ORs for death were higher and more significant during the occurrence of the Alpha variant.

Among the symptoms related to Alpha and Delta variant, fever, cough, and sore throat obtained significant results with ORs of 3.7, 4.3, and 1.2, respectively. Digestive symptoms like diarrhea and vomiting were significant with ORs of 2.7 and 0.6, respectively. Acute kidney failure also elicited a significant OR of 2.9.

The team noted significant comorbidities related to respiratory and cardiovascular disorders with an OR of 3.0 and 1.3, respectively. Finally, the researchers analyzed that vaccination manifests significant results, with half–vaccinated and non-vaccinated cases showing an aOR of 5.6 and 3.7, respectively.

Conclusion

The findings of the study demonstrated the higher occurrence of more severe cases during the predominance of the Alpha variant as compared to the Delta wave after adjusting the regression model for effects like age and status of vaccination.

During the Alpha wave, the frequency of peculiar symptoms (like cough, fever, and vomiting), the number of ICU admissions, and the risk of mortality increased owing to SARS-CoV-2 affecting the elderly population more and the lack of COVID-19 vaccination.

This research work highlights the need for new studies to determine the effectiveness of COVID-19 vaccines against newly emerging SARS-CoV-2 variants.

*Important notice

Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Florensa, D. et al. (2022) "Severity of Covid-19 Cases in the Months of Predominance of the Alpha Variant and the Role of Vaccination". Research Square. doi: 10.21203/rs.3.rs-1276284/v1.

Sangeeta Paul

Written by

Sangeeta Paul

Sangeeta Paul is a researcher and medical writer based in Gurugram, India. Her academic background is in Pharmacy; she has a Bachelor’s in Pharmacy, a Master’s in Pharmacy (Pharmacology), and Ph.D. in Pharmacology from Banasthali Vidyapith, Rajasthan, India. She also holds a post-graduate diploma in Drug regulatory affairs from Jamia Hamdard, New Delhi, and a post-graduate diploma in Intellectual Property Rights, IGNOU, India.

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