Low awareness of past SARS-CoV-2 infection in healthy adults

Researchers of Sanquin found that almost half of the individuals that tested positive for antibodies against the corona-virus (SARS-CoV-2), did not suspect they have had COVID-19, in spite of most of them reporting symptoms. Improved awareness and recognition of COVID-19 symptoms and tracing of asymptomatic contacts is crucial to halting SARS-CoV-2 transmission.

The COVID-19 pandemic challenges governments worldwide to balance appropriate virus control measures and their societal and economic consequences. Crucial to these measures is the individual’s awareness of infection. To this end Sanquin researchers investigated the extent to which healthy plasma donors suspected having had COVID-19 and how the symptoms they experienced relate to antibodies indicative of a past infection with the virus.

11% asymptomatic

For this cross-sectional study, plasma donors anywhere in the Netherlands between May 11th and 18th were screened for total SARS-CoV-2 antibodies using a Wantai ELISA and were invited to participate in an online questionnaire about COVID-19-related symptoms and awareness. Antibody and questionnaire data were complete for 3,676 individuals, including 239 (6.5%) that tested positive for SARS-CoV-2 antibodies. The researchers show that 27% of the individuals with antibodies reported having had only very mild symptoms and 11% had no symptoms at all at any time during the peak of the epidemic. 

The loss of taste and/or smell in particular was significantly associated with seropositivity. Asking about their awareness of having been infected with SARS-CoV-2, 48% of antibody-positive individuals did not suspect having been infected. ”In spite of most of them reporting symptoms”, states lead-investigator Katja van den Hurk. “It appears that people find it difficult to recognize whether or not they have had COVID-19. The main reason for this was that individuals attributed their symptoms to a common cold or hay fever”.

Immediate testing

On the other hand, also donors negative for SARS-CoV-2 antibodies reported COVID-19-like symptoms. Van den Hurk: “Of all donors that thought they have had COVID-19, only 20% tested positive for SARS-CoV-2 antibodies. This does not necessarily mean that the other 80% had not been infected, but this discrepancy indicates that without testing, people might mistakenly think they have been cured of COVID-19 and are now immune to SARS-CoV-2”.

On the basis of this research, which has been submitted for publication, Sanquin supports the call of the Municipal Health Services (GGDs) to test immediately in the event of symptoms and to always cooperate in contact research. Even without symptoms.

The results of this research can be read at https://www.medrxiv.org/.