New cases of severe, long-term COVID appear to be falling — and vaccination likely to be key

term “long covid” is used to describe symptoms or illness that persist for more than four weeks after a positive COVID test or the initial onset of symptoms. Some examples include ongoing loss of taste or smellexhausting fatigueand even suffered heart or the brain.

Prolonged COVID can seriously affect people’s quality of life and ability to work. And there are no proven treatments, which means we may face a wave of disability with little we can do to help.

But in new papermy colleagues and I report that the number of referrals for more severe cases of long-term COVID has decreased over the past year, despite the large waves of delta and omicron infections.

In this study, we looked at referrals to the Long-Term Care COVID Clinic at Cambridge University Teaching Hospital between August 2020 and June 2022. These patients are on the more severe side of the long-term spectrum of COVID symptoms and were referred following assessment by a specialist team following a the appearance of symptoms after at least five months.

We found a 79% decrease in clinic referrals from August 2021 to June 2022 compared to August 2020 to July 2021.

Our study is naturally limited by its small size. It includes data from only 145 patients, and these people are local to the area around Cambridge. I look forward to seeing if other research groups from clinics around the world notice similar trends.

Vaccination and long COVID

There may be other reasons for the positive trend we are witnessing, but time shows that vaccination is the most likely explanation. The decline in claims began in August 2021, about five months after the British public began receiving second doses of the COVID-19 vaccine.

This graph, showing the average number of long COVID advisories before and after this point, highlights the clear connection between the two.

There is already some evidence to suggest that vaccination-derived immunity protects against ongoing COVID, although the size of the effect varies between studies.

For example, one study from the US showed a 15% reduction in long-term COVID symptoms after vaccination, study from Great Britain saw a 50% reduction, while one study with Israel found that vaccination had no lasting symptoms of COVID at all.

The reason for these differences is largely due to testing methods. For example, how long after COVID-19 have researchers studied symptoms? What symptoms constitute ongoing COVID and how severe do these symptoms have to be to qualify?

Although it is difficult to determine the extent to which vaccination reduces ongoing symptoms of COVID, we believe that it has played a key role in reducing the number of new readmissions we have seen in our clinic. The fact that other groups, using different measurement methods, have also observed this association is very encouraging.

Reinfections

We are now in the pandemic phase where re-infection is becoming more common and will likely soon account for the majority of infections.

This brings us to an important question: Does re-infection carry the same risk (or even an increased risk) of long-lasting COVID compared to previous infections? If that happens, we’re going to be in big trouble each re-infection will result in more and more people presenting with lingering COVID-19, ultimately overburdening health services.

But this suggests that previous infections have nothing to do with continued risk of COVID. Actually, we have to consider other factors.

First, there is the possibility that some people are predisposed (as well as not predisposed) to prolonged COVID. Research has already found a number of factors that predict long-term risk of COVID, such as previous infections with other viruses such as Epstein-Barr virus.

I have yet to see studies linking long COVID to genetics, but I would be surprised if there weren’t genetic factors that predispose a person to long COVID.

If some people are indeed prone to long-term exposure to COVID, those people are more likely to develop persistent COVID from the first infection, while others will never develop persistent COVID, even after repeated infections. So multiple COVID infections may not be that risky.

Another possibility is that immunity to SARS-CoV-2 (the virus that causes COVID-19) may protect against prolonged COVID. Each subsequent infection will have a lower chance of causing long-lasting COVID compared to the first infection as immunity builds.

While the trend we’ve seen backs this up (in that the number of COVID cases would have been much higher later). reinfection), it is not yet clear whether immunity from prior infection protects against long-term COVID infection, and whether re-infection with SARS-CoV-2 carries the same risk of long-term COVID infection as primary infection.

Studies from the USA suggests that the risk of long-term COVID accumulates with each re-infection, so more infections mean more risk. However, the definition of ongoing COVID in this study is very broad, including any symptoms beyond six months. It is also a preprint, meaning the results have not yet been reviewed by other scientists.

However, evidence suggests that reinfection is less likely to increase the risk of ongoing COVID than initial infection. Therefore, although every re-infection is not without risk, the risk may be somewhat lower compared to the first infection.

Read more:
Long COVID: New research suggests vaccination may reduce symptoms

We are certainly not out of the woods yet. We know that immunity to SARS-CoV-2, both from vaccination and previous infections, wanes over time. The number of persistent COVIDs may begin to rise as the population’s immunity declines. We will need to monitor this situation closely and continue to focus on booster vaccines.