Almost half of people who have been infected with coronavirus were still reporting problems three months after they had the alpha and delta variants of the virus, Dutch public health institute RIVM said on Tuesday.

The most common problems reported include fatigue, concentration problems and loss of smell, the RIVM said in a preliminary report into the long-term impact of coronavirus.

The under 65s who had recovered from coronavirus and who had been fully vaccinated were less likely to report problems with smell and taste but there was no difference between people who were not, were partially or fully vaccinated at the time of the infection.

The results have been derived from a questionnaire involving over 14,500 people, of whom nearly 9,200 applied to take part in the study between May and December last year. A further 5,400 people who had not had coronavirus took part as a control group.

People who had coronavirus were ‘significantly’ more likely to report problems such as fatigue and shortness of breath than the control group and in 28% of cases, the fatigue was so severe people could not function normally.

‘The effectiveness of the various coronavirus vaccines against hospital and ICU admission has been demonstrated worldwide but whether and to what extent vaccination also protects against long-term complaints is less clear,’ the RIVM said.

Other studies

Other international studies into the effectiveness of vaccination against long-term complaints show varying results and further research is therefore needed to be able to make substantiated statements, the RIVM said.

The complaints, such as fatigue and being short of breath, were also widely reported by people who had not had coronavirus or who had other respiratory problems. It will, therefore, be a challenge for healthcare providers to determine what complaints were caused by Long Covid, or post-Covid and what by something else, the agency said.

The research team will continue to follow the survey respondents and the next update will also include the impact of the Omicron variant, the RIVM said.