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Guest blog: Vaccinations help prevent long COVID symptoms

21.02.2023

Mika Rämet

Long-term coronavirus symptoms i.e. ‘long COVID’ are a significant detriment of a SARS-CoV-2 infection. These long-term symptoms are most often reported after severe COVID infections that have required hospital treatment, but long COVID symptoms may also occur after an acute infection with less severe symptoms. The overall picture of the effect of vaccines against long COVID has been somewhat unclear, but has now been clarified by a US study, which was published in Nature Medicine.

Vaccinated people can also develop long-term COVID symptoms

The study was based on the health data of USA veterans from January to December 2021, i.e. the time before the omicron variant became more prevalent. The study was based on about 34,000 vaccinated people (90% of them male), who had contracted a breakthrough infection, i.e. fallen ill with COVID despite being vaccinated. Their risk of getting various illnesses after a breakthrough infection (BTI) during a six-month control period was compared to two other groups: unvaccinated people who had been infected (113,000 people) and people who had not been diagnosed with a COVID infection (more than 13 million people). The results show that those with a BTI despite being vaccinated (34,000) had significantly more health issues than the control group of uninfected people (13 million). They were assessed to have about 13 additional deaths and 122 conditions considered as a symptom of long COVID for every 1,000 people.

For example, 15 additional cases of exhaustion, a typical symptom of long COVID, were reported per thousand people. The increase was especially high in cardiovascular conditions, mental health disorders and digestive system and respiratory system illnesses. A noteworthy result was that even BTIs with mild symptoms (requiring no hospitalization) increased the risk of particularly atrial arrhythmias and pulmonary embolism.

COVID vaccines significantly reduce the risk of long-term symptoms

It is undeniable that vaccinated people do get breakthrough infections. Research shows that the risk of symptoms after the acute coronavirus infection is strongly dependent on how severe the infection originally was.

For example, if the incidence of the typical symptom of long COVID, exhaustion, increased by less than 8±3 cases per thousand people with mild infections, this risk became multiplied for people with more severe infections (about 45 excess cases per thousand people for those requiring hospitalization and 67 excess cases per thousand people admitted to an intensive care unit). Based on Finnish studies, it is known that three vaccine doses practically prevent severe infections requiring hospitalization among working-age people. Based on this, vaccines can be seen as a key measure in reducing the long-term health effects of a SARS-CoV-2 infection.

Based on the published US study, about 12% of COVID vaccinated people had increased morbidity during a follow-up period of six months when compared to the control population. However, this does not mean that 12% of Finnish people with COVID vaccinations would suffer from increased morbidity after being exposed to the SARS-CoV-2 virus. This is due to several reasons:

 

  1. Getting long-term symptoms is the likelier the more difficult the infection was during its acute stage. It is proven that the vaccines protect people very well against severe COVID infections in Finland.
  2. In the study, the average age of people with a breakthrough infection was nearly 67. The elderly and aging people are at a clearly higher risk of a severe infection than younger people, and therefore they are also at a higher risk of suffering from long-term detriments.
  3. In the study, a vaccination gave only a small protective boost (about 15%) against developing further illnesses after a breakthrough infection during the six-month control period. However, it should be noted that this study was conducted before the omicron variant became more widespread, which means that the vaccines also reduced the risk for a symptomatic SARS-CoV-2 infection. This means that a large part of the vaccinated people did not develop acute or long-term COVID symptoms. This also explains why the research material had noticeably more proven coronavirus infections among non-vaccinated people (more than 113,000 cases) than among vaccinated people (around 34,000 cases).
  4. The COVID infection caused by the omicron variant causes milder symptoms in people without underlying medical conditions than the infections caused by the previous variants. If the likelihood of developing long-term symptoms is dependent on the severity of the illness also in case of the omicron variant, the risk of prolonged symptoms is then lower than in the previous variants.

Vaccines help reduce the likelihood of long-term consequences also in breakthrough infections. However, it is especially significant that vaccinated people are at a clearly reduced risk of getting a severe illness – also in the case of long-term symptoms. Reducing the risk of long-term COVID symptoms is one strong argument for why we should all take the recommended COVID vaccines.
 

Text: 
Mika Rämet 
Professor of Paediatrics and Experimental Immunology ​