Long Covid appears to manifest as a post-viral syndrome of no greater incidence or severity than seasonal influenza, finds new research. However, the similarity observed is only valid for people who are vaccinated, according to the study, being presented at this year's European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) held in Copenhagen, Denmark between April 15 and 18.
The study by researchers at Queensland Health in Australia suggests that despite the similarity of clinical outcomes after Covid-19 and influenza, long Covid's impact on public health systems is likely to stem from the volume of those infected with SARS-CoV-2, rather than the severity of long Covid symptoms.
"In our highly vaccinated population, the public health impact of long Covid does not appear to result from any unique property of SARS-CoV-2. Rather, the impact results from the sheer number of people infected over a short period of time," said Dr John Gerrard, Queensland's Chief Health Officer.
Long Covid is a complex, multi-system condition that develops during or after having Covid, and is used to describe symptoms that continue for 4-12 weeks and longer-term sequelae beyond 12 weeks known as post-Covid syndrome.
Breathlessness, a cough, heart palpitations, headaches, and severe fatigue are among the most prevalent symptoms. Long Covid has the potential for a substantial impact on society, from increased health care costs to economic and productivity losses.
During concurrent waves of Omicron and influenza that occurred in mid-2022, 2,195 adults diagnosed with Covid-19 and 951 adults diagnosed with influenza were followed for 12 weeks and asked about ongoing symptoms and functional impairment using a questionnaire delivered by SMS link to a survey.
At the time, more than 90 per cent of the population of Queensland had been vaccinated against Covid-19.Of those diagnosed with Omicron, a fifth (21 per cent) reported ongoing symptoms at 12 weeks and 4 per cent reported having moderate to severe functional limitations in everyday life.
Similarly, around a fifth (23 per cent) of adults diagnosed with influenza reported ongoing symptoms and 4 per cent reported moderate to severe functional limitations.The analysis found no evidence to suggest that adults with Omicron were more likely to have ongoing symptoms or moderate to severe functional limitations at 12 weeks after their diagnosis than adults who had influenza.
Interestingly, the analyses suggest that younger age groups and non-indigenous populations were more likely to report moderate to severe functional limitations after influenza than Omicron. The study also has several limitations including that it was observational and can't prove causation and it can't rule out the possibility that other unmeasured factors such as underlying illness and influenza vaccination status may have influenced the results.