British Study Warns That Infection With The SARS-CoV-2 Delta Variant Doubles The Risk Of Hospitalization When Compared To The Alpha Variant
A new study by researchers from Public Health England(PHE) and the University of Cambridge has confirmed that the Delta variant doubles the risk of hospitalization when compared to alpha variant and warns that disease severity also often accompany infections with the Delta variant.
The B.1.617.2 variant also known as the Delta variant
was first detected in England in March, 2021. It has since rapidly become the predominant lineage, owing to high transmissibility. It is suspected that the delta variant is associated with more severe disease than the previously dominant alpha (B.1.1.7) variant. The study team aimed to characterize the severity of the delta variant compared with the alpha variant by determining the relative risk of hospital attendance outcomes.
Individual-level data on 43,338 COVID-19-positive patients (8,682 with the delta variant, 34,656 with the alpha variant; median age 31 years [IQR 17–43]) were included in the study analysis.
196 (2·3%) patients with the delta variant versus 764 (2·2%) patients with the alpha variant were admitted to hospital within 14 days after the specimen was taken (adjusted hazard ratio [HR] 2·26 [95% CI 1·32–3·89]). 498 (5·7%) patients with the delta variant versus 1,448 (4·2%) patients with the alpha variant were admitted to hospital or attended emergency care within 14 days (adjusted HR 1·45 [1·08–1·95]). Most patients were unvaccinated (32,078 [74·0%] across both groups). The HRs for vaccinated patients with the delta variant versus the alpha variant (adjusted HR for hospital admission 1·94 [95% CI 0·47–8·05] and for hospital admission or emergency care attendance 1·58 [0·69–3·61]) were similar to the HRs for unvaccinated patients (2·32 [1·29–4·16] and 1·43 [1·04–1·97]; p=0·82 for both) but the precision for the vaccinated subgroup was low.
The study findings revealed that a higher hospital admission or emergency care attendance risk for patients with COVID-19 infected with the delta variant compared with the alpha variant.
The study findings were published in the peer reviewed journal: The Lancet Infectious Diseases https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00475-8/fulltext
The study involving more than 40,000 cases in England during the period between 29 March and 23 May 2021 confirmed that individuals infected with the SARS-CoV-2 delta variant have approximately double the risk of hospitalization compared with those infected with the alpha variant.
It was also found that the risk of attending hospital for emergency care or being admitted to hospital within 14 days of infection with the delta variant was also one and a half times greater compared with the alpha variant (1.45-fold increase in risk).
This is the first study to report hospitalization risk for the delta versus alpha variants based on cases confirm
ed by whole-genome sequencing, which is the most accurate way to determine the virus variant.
Lead author, Dr Gavin Dabrera, a Consultant Epidemiologist at the National Infection Service, Public Health England, told Thailand Medical News, "This study confirms previous findings that individuals infected with Delta are significantly more likely to require hospitalization than those with Alpha, although most cases included in the analysis were unvaccinated. We already know that vaccination offers excellent protection against Delta and as this variant accounts for over 98% of COVID-19 cases in the UK, it is vital that those who have not received two doses of vaccine do so as soon as possible. It is still important that if you have COVID-19 symptoms stay home and get a PCR test as soon as possible."
This new variant which is currently wreaking havoc globally was first reported in India in December 2020 and early studies found it to be up to 50% more transmissible than the variant of COVID-19 that had previously gained dominance worldwide, known as the alpha variant, first identified in Kent, UK.
Another study from Scotland preliminarily reported a doubling in risk of hospitalization with the delta variant compared with the alpha variant and it is suspected that delta is associated with more severe disease. The study used patients' initial PCR test results and determined which variant they had by testing for a specific gene that is more common in the delta variant. https://pubmed.ncbi.nlm.nih.gov/34139198/
For the current study, the research team analyzed healthcare data from 43,338 positive COVID-19 cases in England between 29 March and 23 May 2021, including information on vaccination status, emergency care attendance, hospital admission, and other demographic characteristics. In all cases included in the study, samples of the virus taken from patients underwent whole genome sequencing to confirm which variant had caused the infection.
It was found that during the study period, there were 34,656 cases of the alpha variant (80%) and 8,682 cases of the delta variant (20%). While the proportion of delta cases in the study period overall was 20%, it grew to account for around two thirds of new COVID-19 cases in the week starting 17 May 2021 (65%, 3,973/6,090), indicating it had overtaken alpha to become the dominant variant in England.
The study team found that around one in 50 patients were admitted to hospital within 14 days of their first positive COVID-19 test (2.2% alpha cases, 764/34,656; 2.3% delta cases, 196/8,682).
Upon accounting for factors that are known to affect susceptibility to severe illness from COVID-19, including age, ethnicity, and vaccination status, the researchers found the risk of being admitted to hospital was more than doubled with the delta variant compared with the alpha variant (2.26-fold increase in risk).
Numerous studies have shown that full vaccination prevents both symptomatic infection and hospitalization, for both alpha and delta variants.
However in this study, only 1.8% (794/43,338) of COVID-19 cases (with either variant) had received both doses of the vaccine; 74% of cases (32,078/43,338) were unvaccinated, and 24% (10,466/43,338) were partially vaccinated.
The study team stressed that it was not possible to draw statistically significant conclusions about how the hospitalization risk differs between vaccinated persons who later develop alpha and delta infections.
The findings from this study therefore primarily tell us about the risk of hospital admission for those who are unvaccinated or partially vaccinated.
Co-Lead author, Dr Anne Presanis, a senior statistician at the MRC Biostatistics Unit, University of Cambridge, explained, "Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic. Getting fully vaccinated is crucial for reducing an individual's risk of symptomatic infection with Delta in the first place, and, importantly, of reducing a Delta patient's risk of severe illness and hospital admission."
The study team also highlighted several limitations to the study. Some demographic groups may be more likely to seek hospital care, which could have biased the results, and there may have been changes in hospital admission policy during the period of the study, although adjustment for demographics and calendar time should have minimized such bias. In addition, the authors did not have access to information about patients' pre-existing health conditions, which are known to affect the risk of severe illness from COVID-19. They accounted for this indirectly using age, gender, ethnicity, and estimated level of socioeconomic deprivation.
The study team concluded, “To our knowledge, this study is the largest assessment of hospitalization risk for the delta variant using cases confirmed by whole-genome sequencing, providing important foundational evidence of increased risk compared with the alpha variant. Before the emergence of the delta variant, the evidence base largely focused on the alpha variant and its higher transmissibility and severity when compared with previous wildtype strains. Further research is needed to clarify if the hospitalization risks differ in vaccinated individuals infected with the delta variant compared with the alpha variant. The findings so far suggest that outbreaks of the delta variant in unvaccinated populations might lead to a higher health-care burden, particularly compared with the previous prevalent SARS-CoV-2 strains. The findings are key for resource planning and policy decisions to mitigate the impact of the delta variant in the UK, where the delta variant now dominates, and in other high-income countries where the rapid spread of the delta variant might occur.”
For the latest research of the Delta Variant,
keep on logging to Thailand Medical News.