The risk of developing long-term symptoms after a SARS-CoV-2 infection has decreased since the pandemic. These findings are from research conducted by RIVM in the VASCO study. Researchers in this study have been monitoring tens of thousands of people in the Netherlands over an extended time period. Persistent symptoms after a SARS-CoV-2 infection are also known as post-COVID or Long COVID. The risk of long-term symptoms after COVID-19 is expected to remain lower from now on.
The study compared two groups of more than 5,000 people each. One group consisted of people who had had COVID-19 in autumn 2023, while the other group consisted of people who did not have COVID-19 in that same period.
Almost no difference between infected and non-infected participants
Every three months, the participants reported whether they had specific symptoms, such as tiredness, difficulty during exertion, or concentration problems. The researchers looked at the number of people with new symptoms after three, six, nine and twelve months. The results showed that there was almost no difference the two groups – those who had had COVID-19, and those who had not.
Persistent symptoms mainly reported in the first few months
Participants were also able to indicate whether they thought that their symptoms were caused by the coronavirus SARS-CoV-2. People who had had COVID-19 were more likely to indicate persistent symptoms caused by SARS-CoV-2 in the first three to six months after the infection, compared to participants who had not had a SARS-CoV-2 infection. After nine months, this difference had vanished.
Causes for lower risk of post-COVID
Many people in the Netherlands have already had COVID-19 vaccinations and/or one or more SARS-CoV-2 infections before. As a result, they have built up protection against the virus. This may be the cause for the reduced risk of persistent symptoms. The coronavirus SARS-CoV-2 has also changed over time.
For people who get COVID-19 now, it is important news that the risk of post-COVID has become much lower. Even so, it is not possible to state that it is now impossible for people to develop post-COVID symptoms after a SARS-CoV-2 infection. Similarly, the results of this study do not offer any information about people who developed post-COVID symptoms before this, and have sometimes had a slow and difficult recovery process. About 400,000 people in the Netherlands have reported having symptoms as a result of post-COVID. Approximately 100,000 people have severe post-COVID symptoms.
Research on symptoms before and after infection
Previous studies on post-COVID mainly looked at the symptoms that people reported after a SARS-CoV-2 infection. Those results were then compared to the symptoms of people who had not had an infection. In this VASCO study, the researchers also looked at any symptoms that participants had already had before their infection. This gave researchers a better understanding of which symptoms were new, and could therefore have been caused by a new SARS-CoV-2 infection.
Read the scientific article presenting all the results of this study: Post-COVID-19 condition in individuals infected with SARS-CoV-2 in autumn 2023 in the Netherlands: a prospective cohort study with pre-and post-infection data.