Thread by @ZdenekVrozina

Even in the Omicron era, long COVID remained common. A preprint meta-analysis showing that the burden persisted, even as the symptom profile shifted.🧵

This study is interesting because it does not just ask how common long COVID is. It looks at two things at the same time.
Which SARS-CoV-2 variant caused the infection, and how long after infection symptoms were assessed.

They included 35 studies with a total of about 159,000 people. Overall, long COVID showed up in about 28.5% of cases. It was more common after pre-Omicron infections, where the prevalence was around 35.5%, than after Omicron infections, where it was about 22.8%!

What also stands out is that nearly 30% of cases still had symptoms more than 6 months later.

Even more importantly, the symptom pattern itself seems to shift depending on the variant. Pre-Omicron infections were more strongly linked with shortness of breath and loss of smell, while Omicron was more associated with brain fog and paresthesia.

One of the key findings from the paper is that neurotropism appears to persist into the Omicron era. Long COVID did not disappear, and neurological and cognitive symptoms remained a prominent part of its presentation, even as the broader symptom profile evolved across variants and over time.

One very consistent finding was that fatigue remained the most common symptom across variants and across follow-up periods. Other frequent symptoms included brain fog, shortness of breath, and sleep problems.

Another striking point is that when the authors compared people assessed within 6 months versus after 6 months, the overall prevalence did not really drop much. About 27.3% vs 29.9%.

So at the level of pooled data, there was no clear sign that long COVID simply fades away with time. That matters, because it pushes back against the assumption that most people will automatically recover if they just wait long enough.

The symptom profile also seemed to evolve over time. In the earlier period, symptoms such as sleep disturbances, headache, and to some extent skin-related symptoms were more common. In longer follow-up, malaise and difficulty swallowing became more prominent.

The authors suggest this could reflect later-developing systemic or autonomic effects, meaning long COVID may be more than just the tail end of an acute infection. It may actually change form over time!

The highest overall prevalence appeared in people with pre-Omicron infections assessed within 6 months, at around 42.4%. The lowest was in Omicron cases assessed within 6 months, at around 18.5%. But the symptom patterns were quite distinct.

Early pre-Omicron cases had more sleep problems and headaches,
longer-term pre-Omicron cases had more shortness of breath, smell loss, runny nose, malaise, eye symptoms, nausea, and swallowing difficulties,
while early Omicron cases showed more brain fog and paresthesia.

That may be the most compelling finding of the whole paper. Pre-Omicron long COVID seems more respiratory and sensory, while Omicron-related long COVID looks more neurocognitive and systemic.

This could matter clinically! Follow-up and care might need to be more targeted depending on which variant likely caused the infection.

The paper challenges the idea that long COVID is a fixed syndrome. Instead, the authors describe it as a dynamic and heterogeneous condition, shaped by viral evolution, host immunity, and time since infection.

Yes, the study has some limitations. A lot of the data came from self-reported symptoms, which can introduce bias. In many studies, the variant was not confirmed by genomic sequencing, but inferred from the time period in which infection occurred.

Lugtu at al., Prevalence of Post-COVID Symptoms Across Variants of Concern and Follow-up Periods: A Systematic Review and Meta-Analysis. ijidonline.com/article/S1201-…

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