Researchers have determined that the risk of death from Covid-19 infection is still higher than it is from flu.
Using data from the Clinical Epidemiology Centre, VA St Louis HealthCare System, in Missouri, researchers wrote in their research letter in JAMA Network that in the first year of the pandemic, the mortality risk for people hospitalised with Covid-19 was substantially higher than in people admitted to a facility for seasonal influenza.
The risk of death from Covid infection has since declined.
However, in autumn-winter 2022-2023, patients admitted to hospital for Covid had a 60% higher risk of death compared with those hospitalised for seasonal influenza.
They wrote that new variants of SARS-CoV-2 have continued to appear, including the emergence of JN.1, the predominant variant in America since 24 December 2023.
This latest study evaluated the risk of death in a cohort of people hospitalised for Covid or for seasonal influenza in autumn-winter 2023-2024.
Based on US Department of Veterans Affairs electronic health records from all 50 states, they identified people who were admitted to the hospital with a diagnosis of Covid-19 or seasonal influenza between 1 October 2023 and 27 March 2024, and within two days before and 10 days after a positive test result for SARS-CoV-2 or flu.
Patients with either infection admitted for another reason or those hospitalised for both Covid and seasonal influenza were excluded.
The cohort was followed up for 30 days, until death, or until 31 March 2024. Baseline characteristics between patients hospitalised for Covid-19 vs influenza were compared using absolute standardised differences: a standardised difference less than .01 suggests good balance.
The team adjusted for differences in baseline characteristics between the groups using inverse probability weighting. Logistic regression was used to calculate a propensity score (probability of being assigned to the Covid-19 group) that was then applied to balance the two groups.
Weighted Cox survival models were used to estimate the difference in risk of death between Covid-19 and seasonal influenza groups. Results were reported as adjusted death rates and hazard ratios (HRs) with 95% CIs in the Covid-19 group compared with the seasonal influenza group.
The team also examined the difference in risk of death between people hospitalised for Covid-19 before and during the JN.1-predominant era (before vs on or after 24 December 2023). A
Analyses were performed with SAS Enterprise Guide version 8.3 (SAS Institute Inc). They defined statistical significance as a 95% CI that did not cross 1.00.
Results
The cohort included 8 625 participants admitted for Covid-19 (unadjusted death rate, 5.70% at 30 days) and 2 647 participants hospitalised for seasonal influenza (unadjusted death rate, 3.04% at 30 days). The Covid-19 and seasonal influenza groups were balanced after propensity score weighting.
Patients admitted for Covid-19 had a higher risk of death compared with those hospitalised for seasonal influenza (adjusted death rate, 5.70% vs 4.24% at 30 days; adjusted HR, 1.35 [95% CI, 1.10-1.66]).
There was no statistically significant difference in the risk of death among people hospitalised for Covid-19 before and during the JN.1-predominant era (adjusted death rate, 5.46% vs 5.82% at 30 days; adjusted HR, 1.07 [95% CI, 0.89-1.28]).
The findings suggested that JN.1 may not have a materially different severity profile than the variants immediately preceding it.
Study limitations include that the Veterans Affairs population (older age and predominantly male) may not represent the general population and causes of death were not examined.
See more from MedicalBrief archives:
Risk of death from Covid-19 3.5 times higher than from flu — Canadian study
New Covid variant dominates in US
Covid-19 with flu substantially increases risk of severe illness and death
New Covid variant – should we be concerned?
Did Covid ‘viral interference’ keep common flu away?