Vrouw op een bankje in een park

After a SARS-CoV-2 infection involving Omicron, 1 in 10 people still have symptoms three months later. This is almost 2 times lower than after an infection involving the Delta variant. This is evident from new results of the LongCOVID study at RIVM. There is variation in the frequency of specific post-COVID symptoms after an infection with the Omicron or Delta variant. However, the long-term symptoms still have a major impact in both groups. 

Many people infected with Omicron

The Omicron variant often makes people less ill than its predecessor Delta. This variant more easily evades the immunity that people had already developed from previous infections or vaccination. Partly as a result of this factor, many people in the Netherlands contracted COVID-19, some of them not for the first time. The LongCOVID study looked at symptoms that were present three months after an infection involving Omicron. Which symptoms were present and how common were they? The researchers also compared these findings to symptoms after an infection involving the Delta variant.

Tiredness, shortness of breath and brain fog more common after COVID-19

People who had an Omicron infection were more likely to struggle with tiredness, shortness of breath, brain fog, memory problems and difficulty in busy environments, compared to people who had not had COVID-19. However, these symptoms were even more common after a Delta infection. If people had already had COVID-19 previously, they were more likely to be affected by tiredness and shortness of breath, compared to people whose Omicron infection was the first time they had COVID-19.

Because Omicron is more infectious than Delta, it caused more people to become ill overall. As a result, the total number of people with long-term symptoms after an Omicron infection may be higher, despite the milder course of illness. For that reason, post-COVID (or Long COVID) continues to be a common and high-impact condition among people in the Netherlands. 

Structure of the study 

The survey-based study compared the results of the following groups of people in the Netherlands:

  • 4,138 people who had a SARS-CoV-2 infection involving the Omicron variant between January and May 2022.
  • A control group of 4,398 people who did not have a SARS-CoV-2 infection. 
  • 6,855 people who had a SARS-CoV-2 infection involving the Delta variant between July and December 2021. 

Three months after the infection, the participants completed a survey. The questions were about 41 health problems. The survey also included questions about the severity of the tiredness, shortness of breath, cognitive problems and physical pain. 

Comparing symptoms between the different groups

Since some long-term symptoms also occurred in the control group, the study looked at which symptoms occurred with statistically significant frequency in people who had had an Omicron infection. Researchers determined the percentage of people who had long-term symptoms resulting from COVID-19 (i.e. people with Post-COVID or Long COVID) based on the difference in how common these symptoms were in people after Omicron and in people who did not have COVID-19, and/or had never previously had COVID-19.

Next step: current condition one year after COVID-19

The LongCOVID study has been looking at perceived symptoms three months after an Omicron infection. The next step is to assess the impact of COVID-19 after one year.