RIVM: three months after Covid-19, half still have complaints

Almost half of the people who experienced mild or moderate Covid-19 still have one or more complaints after three months, such as fatigue, difficulty concentrating or loss of smell. That is more often than people after another respiratory infection, of whom 30 percent have long-term complaints. And it is almost twice as often as in people who have not had an infection, of whom a quarter report such complaints.

RIVM reports this on the basis of interim results of their ongoing lung covid study. The study has appeared in preprint and has yet to be reviewed by independent scientists.

The RIVM researchers presented questionnaires with 41 symptoms to more than 9,000 people who had registered for the study after a positive test result. They received the questionnaire within a week of the result, i.e. shortly after the infection. Almost all participants had corona symptoms and experienced mild to moderate Covid-19 at home, ten patients had to go to hospital. More than 5,400 people who did not have corona took part as a control group. These were people who had a negative test result – so their respiratory symptoms were probably caused by another virus – and people who had never been infected.

After three months, 13 of the 41 symptoms were clearly more common in the corona patients than in the control group. Fatigue in particular was frequently reported (31 percent), followed by shortness of breath (16 percent), difficulty concentrating (15 percent), difficulty being in a crowded environment (13 percent), and problems with smell (12 percent). In most people, the complaints were so severe that they interfered with their normal daily activities.

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Vaccine partially protects

Vaccination lowers the risk of lung covid, but how much is not yet clear: studies see 15 to 50 percent protection. In the RIVM study, too, vaccination only partially protected against long-term complaints. Fully vaccinated people younger than 65 years reported less smell or taste loss after three months, but for other long-term complaints there was no difference between people who were vaccinated, partially or not.

In many studies into lung covid for which people can register themselves, relatively much higher educated women take part. The percentages are therefore not completely representative of the general population. Relatively much higher educated women also participate in this study, says epidemiologist Tessa van der Maaden, who leads the lung covid study of the RIVM. “But we corrected for this as much as possible by taking people who are similar in age and sex as a control group.”

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The high percentage is not unexpected, she says. “The percentage we find, 48 percent, falls within the range that other major scientific analyzes report on complaints that persist for more than three months, between 29 and 55 percent.”


The RIVM investigation ran from May to December 2021, when there were mainly infections with the Alpha and Delta variants of the coronavirus. In a follow-up study, RIVM will examine to what extent the results found also apply after infection with the Omikron variant, which has been dominant from December 2021.

British researchers published their first observational study this week in The Lancet† They compared the risk of lung covid (defined as symptoms persisting for more than four weeks) in fully vaccinated people after an infection with Delta (from June to November 2021) or Omikron (from December 2021 to March 2022). Participants reported their complaints themselves in an app.

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This shows that the risk of lung covid is significantly lower after Omikron than after Delta: 4.5 percent of the participants in the Omikron group still reported complaints after four weeks, compared to 10.8 percent in the Delta group. The latter percentage is lower than that in the RIVM study, partly because all participants in the British study were fully vaccinated and also included people who tested positive and had no symptoms.

The low percentage of lung covid after Omikron is a windfall, but the number of Omikron infections worldwide was many times higher from January to April than in previous contamination peaks, and a next peak is expected. The British therefore warn that the absolute number of people with lung covid will inevitably rise in the future.



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