Researchers presented a complete method for estimating long coronavirus disease (COVID)-associated morbidity in the Australian population in a recent study published in the International Journal of Epidemiology.
The method examined the time of dominance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant of concern (VOC) between 2021 and 2022.
Background
Post-COVID-19 condition (PCC) or long COVID symptoms appear in a significant percentage of people following acute COVID 2019 (COVID-19), but less frequently in the post-acute phase of Omicron VOC infections than Delta VOC infections in vaccinated individuals.
Given the global increase in SARS-CoV-2 transmission, it is important to quantify the burden of COVID-19 and the associated long-term consequences.
Prior estimates of pre-Omicron VOC-associated PCC were reported, analyzing only main symptoms, lacking appropriate control groups, and thus failing to recognize the true extent and heterogeneity of PCC symptomatology.
The lack of high-quality data on PCC symptoms clearly prevents quantifying the global PCC burden. Furthermore, the majority of long-term COVID studies included unvaccinated people infected during the pre-Omicron VOC period.
Concerning the research
The current study provided complete estimates of long COVID-associated morbidity by analyzing individual PCC symptoms in Australia during Omicron dominance.
To accurately quantify PCC effects among COVID-19 vaccinees during Omicron dominance, differences in PCC risks were assessed based on COVID-19 vaccination status and SARS-CoV-2 VOC.
PCC-associated morbidity caused by Omicron infections was calculated by evaluating the start, severity, and duration of each PCC symptom. PCC-related years lived with disability (YLDs) during the predominance of Omicron BA.1 and BA.2 were calculated by analyzing data from prior cross-sectional, cohort-based, and case-control studies, which determined the duration and prevalence of each PCC symptom.
The predicted health losses were compared to the years lived with disability linked with acute COVID-19 infections and the years of life lost (YLLs) due to SARS-CoV-2 infections.
COVID-19-associated disability-adjusted life years (DALYs) were calculated by adding the components and comparing them to DALYs associated with other diseases documented in the global burden of disease (GBD) study 2019.
Long COVID symptom severity was quantified as disability weights (DW), as described in the global burden of disease study. To assess long COVID symptom prevalence among COVID-19 vaccinees, base case prevalence estimates for unvaccinated and pre-Omicron VOC-infected people were multiplied by an odds ratio (OR) of 0.6.
incidence figures were multiplied by 0.3, based on an estimate of reductions in the incidence of any long COVID symptom 4.0 weeks post-Omicron VOC infection versus Delta VOC infection among COVID-19 vaccinees in the United Kingdom.
The PCC YLDs were determined by multiplying the expected PCC-associated morbidity for each symptomatic infection by the number of symptomatic BA.1 and BA.2 infections between December 10, 2021, and April 9, 2022.
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The researchers ran sensitivity tests by changing the incidence rates of physical, cognitive, and psychological symptoms. In addition, the odds ratio for SARS-CoV-2 Omicron VOC vs. pre-Omicron VOC infections (OR 0.3) was applied to hospitalized patients in an extreme case situation.
Results
During the first four months of Omicron dominance in Australia, five million SARS-CoV-2 infections were recorded, with 35,500 and 3,463 hospital admissions and deaths, respectively, and a predicted 61% of infected people were COVID-19 vaccinees.
PCC caused 5,200 YLDs and acute COVID-19 caused 1,800 YLDs, respectively, suggesting that PCC caused 74.0% of COVID-19-associated YLDs during BA.1 and BA.2 predominance.
SARS-CoV-2 caused 50,900 DALYs, accounting for 2% of the expected DALYs for all diseases during the time, with PCC accounting for 10%. This was contrasted to 3.6% DALYs caused by acute SARS-CoV-2 infection-related morbidity and the remaining DALYs caused by acute SARS-CoV-2 infection-related mortality.
The majority of PCC YLDs were obtained in community settings, with the majority (2,200 YLDs) noted among vaccinated adults, who accounted for 51% of the documented long COVID cases.
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The morbidity associated with COVID-19 was similar to the non-lethal health losses associated with chronic renal disorders and myocardial ischemia. COVID-19 was one of the top ten causes of DALYs in Australia during the study time. Adult COVID-19 vaccinees with no hospitalization need during acute COVID-19 were assessed to have lost 0.10% of a healthy year of life due to PCC (or 33% of one day of healthy life lost).
Sensitivity analyses reduced overall PCC morbidity by 12.0%, to 4,600 YLDs, compared to the primary study. The estimated PCC morbidity was within 20% of the Institute for Health Metrics and Evaluation (IHME) estimate, showing the validity of the current study approach.
Conclusions
Overall, the research findings highlighted PCC effects among Australians using a disease burden-type approach, giving a more accurate estimate of the PCC burden than previously reported studies.
PCC was responsible for 74.0% of the non-lethal loss of health caused by confirmed BA.1 and BA.2 infections in Australia. Increasing PCC symptom data would improve the study’s results’ accuracy.
Furthermore, PCC symptom prevalence is lower in Omicron infections and among COVID-19 vaccinees than in unvaccinated people with pre-Omicron infections.
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When infection estimates are added together, PCC adds to significant health loss regardless of vaccine protection. As a result, PCC must be addressed when developing COVID-19 mitigation policies and strategies.
