Long COVID risk reduced in Omicron vs. Delta

In a recent study published in LancetResearchers at King’s College London and ZOE Limited have assessed the risk of long coronavirus disease (COVID) associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta and omicron variants in the United Kingdom (UK). did.

Studies show that Omicron causes less severe acute SARS-CoV-2 infections, especially among vaccinated individuals, compared to previously circulating mutant infections.However, a large population can develop for a long time COVID symptoms.. Data on the relative odds of long COVIDs among people infected with relatively recent variants such as Delta and Omicron can inform health authorities and policy makers about better allocation of health resources. ..

Correspondence: Risk of long COVID associated with delta vs. omicron variant of SARS-CoV-2.. Image Credit: Donkeyworx / Shutterstock

About research

In a current case-control study, researchers assessed the risk of long COVIDs during periods of delta and omicron dominance among British citizens.

The COVID Symptom Study ZOE application was used to obtain data reported by individuals with flows confirmed by real-time polymerase chain reaction (PCR) or lateral flows. antigen Test-confirmed COVID 2019 (COVID-19) diagnoses after vaccination. Study participants had no history of COVID-19 prior to vaccination and reported more than one log weekly with the ZOE application for more than 28 days.

Only individuals tested positive for SARS-CoV-2 prior to February 10, 2022 were included for individuals who tested positive during the Omicron predominance. Multiple deprivation indices (IMDs) for local areas were calculated to estimate relative local deprivation for both groups of individuals. For the index, a score of 1 indicates the least disadvantaged individual and a score of 10 indicates the least disadvantaged individual.

The study exposure was a period of infection and the study results were a long outbreak of COVID. Long COVID risks such as IMD, gender, age, comorbidities, body mass index (BMI), vaccination status (single, double), using logistic regression modeling to determine the association between outcome and exposure Adjusted the factor data. , Or three times the dose of the vaccine received). The time from the latest vaccination to the onset of SARS-CoV-2 infection was stratified into three groups: 3 months, 3-6 months, and more than 6 months.

result

A total of 56,003 Omicron cases (adults first tested positive for SARS-CoV-2 between 20 December 2021 and 9 March 2022) and 41,361 Delta cases (1 June 2021 November 2021). Adults) 2021) who were first tested positive for SARS-CoV-2 were identified during the 27th day. The proportion of women identified as having Delta (59%) and Omicron (55%) infections was higher than that of men.

However, both groups had participants of similar age (mean age 53 years) with similar presence (19%) of comorbidity. The IMD index showed that cases of the Omicron variant were more prevalent in areas with slightly less deprivation compared to cases of the Delta variant (17% compared to 17.5% of IMD scores 1-3).

Of the Delta and Omicron cases, 2501 (4.5%) and 4469 (10.8%) developed long-term COVID symptoms. Relative odds for long COVIDs were lower for Omicron infections compared to Delta infections at all vaccination timings (odds ratio range 0.2-0.5). Similar results were obtained by performing an age group analysis.

Conclusion

Overall, the findings showed that Omicron-infected individuals had a lower risk of longer COVIDs than Delta-infected individuals. However, the absolute number of long COVID cases in a particular time period depends on the amplitude and shape of the curve that represents the pandemic. Considering the peak of more than 350,000 new and symptomatic COVID-19 Omicron cases per day estimated to occur on March 26, 2022, only a few long COVID cases are estimated by the ZOE app. It is 4.5%, which is the number of long COVID cases. Will only increase in the future.

The authors believe that this study is the first peer-reviewed study to assess the risk of long COVID in Omicron cases. The findings highlight the use of smartphone applications in COVID-19 monitoring. However, further research is needed to determine if unvaccinated children and adults are at increased risk of long-term COVID.

Research limits

Limitations of the study included the use of data reported by the SARS-CoV-2 positive individuals themselves, no direct SARS-CoV-2 test for identification of variants, and objective COVID-19 period. There is no positive result measurement. In addition, the duration of Omicron’s case evaluation was (albeit slightly) shorter than that of Delta’s case. In addition, individuals were unable to assess longer-term COVID risk, for example over 12 weeks.