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By: Ben Krishna, Postdoctoral Researcher, Immunology and Virology, University of Cambridge.
From term “long COVID” is used to describe symptoms or illness that persist for more than four weeks after a positive COVID test or the original onset of symptoms. Some examples include a constant loss of taste or smell, debilitating fatigue, and even ongoing damage to the heart or brain.
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Long COVID can seriously affect people’s quality of life and their ability to work. And there are no proven treatments, meaning we may be facing a wave of disabilities where there’s little we can do to help.
But in a new article, my colleagues and I report that the referrals for more severe cases of long COVID-19 has declined over the past year, despite large waves of delta and omicron infections.
In this study, we looked at references to the long COVID clinic at Cambridge University Teaching Hospital between August 2020 and June 2022. These patients are on the more severe end of the lung COVID symptom spectrum, having been referred after review by a team of specialists after at least five months of symptoms.
We found a 79% decrease in the number of patients referred to the clinic from August 2021 to June 2022, compared to August 2020 to July 2021.
Our study is, of course, limited by its small size. It includes data from just 145 patients, and these people are from the Cambridge area. I’m curious if other research groups from clinics around the world see similar trends.
Vaccination and lung COVID
There may be other reasons for the positive trend we observed, but the timing suggests that vaccination is the most likely explanation. The drop in referrals will begin in August 2021, about five months after the UK population began receiving second doses of COVID-19 vaccines.
There is already evidence that immunity through vaccination protects against long COVID, although the size of the effect differs between studies.
For example, a study from the US showed a 15% reduction in long COVID symptoms after vaccination, a study from the UK saw a 50% reduction, while a study from Israel found vaccination was associated with none at all long COVID symptoms.
The reason for these differences has a lot to do with the testing methods. For example, how long after COVID-19 did the researchers examine the symptoms? What symptoms constitute long COVID, and how severe do these symptoms have to be to qualify?
Although it is difficult to determine to what extent vaccination long COVID symptoms, we believe vaccination has played an important role in reducing the number of new referrals in our clinic. The fact that other groups using different measurement techniques have also observed this association is very reassuring.
Reinfections
We are now in a phase of the pandemic where reinfections are becoming more common and will probably account for most infections soon.
This brings us to an important question: does reinfection carry the same risk (or even an increased risk)? long COVID, compared to previous infections? If yes, then we have a big problem because any reinfection will lead to more and more people with long COVID, ultimately flooding healthcare.
But this assumes that previous infections don’t affect the long COVID risk. In reality, we have to take into account other factors.
First, there is the possibility that some people are more susceptible (and not susceptible) to long covid. Studies have already found a range of factors that long Predicting COVID risk, such as previous infections with other viruses, such as the Epstein-Barr virus.
I haven’t seen a study that long COVID links to genetics, but I’d be surprised if there aren’t genetic factors that predispose someone to long COVID.
If some people indeed have a predisposition for long COVID, then these people will be more likely to develop after a first infection long to develop COVID, while others never long will get COVID even after repeated infections. Multiple COVID infections may therefore not be as risky.
Immunity after infection
Another possibility is that immunity to SARS-CoV-2 (the virus that causes COVID-19) protects against long covid. Each subsequent infection would then have a smaller chance of long more than the first, as immunity builds.
While the trend we observed would support this (in that a much higher number of COVID cases re-infection later), it is not yet clear whether immunity from a previous infection protects against long COVID, nor or reinfections with SARS-CoV-2 same risk of long COVID as a primary infection.
Research from the US suggests that the risk of long COVID increases with each reinfection, so more infections means a higher risk. The definition of long However, COVID in this study is very broad, including all symptoms after six months. It’s also a preprintmeaning the results have not yet been looked at by other scientists.
However, the data suggest that reinfections increase the risk of long COVID less than the first infection. So while any reinfection is not without risk, the risk may be slightly less than a first infection.
We’re definitely not done yet. We know that immunity to SARS-CoV-2, both from vaccination and from previous infections, declines over time. The long COVID rates may begin to creep up as immunity wanes across the population. We will need to monitor this situation carefully and continue to focus on booster vaccines.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The opinions and views expressed in this article are those of the author and do not necessarily reflect the opinions or views of TPO.