SARS-CoV-2 viral-load distribution reveals that viral loads increase with age: a retrospective cross-sectional cohort study

• Published in: International Journal of Epidemiology Vol. 50; no. 6; pp. 1795 - 1803
• Main Authors: Euser, Sjoerd, Aronson, Sem, Manders, Irene, van Lelyveld, Steven, Herpers, Bjorn, Sinnige, Jan, Kalpoe, Jayant, van Gemeren, Claudia, Snijders, Dominic, Jansen, Ruud, Schuurmans Stekhoven, Sophie, van Houten, Marlies, Lede, Ivar, Cohen Stuart, James, Slijkerman Megelink, Fred, Kapteijns, Erik, den Boer, Jeroen, Sanders, Elisabeth, Wagemakers, Alex, Souverein, Dennis
• Format: Journal Article Web Resource
• Language: English
• Published: England Oxford University Press 06.01.2022
• Subjects: Adult; Child; COVID-19; COVID-19 Testing; Cross-Sectional Studies; Humans; Retrospective Studies; SARS-CoV-2; Viral Load; COVID-19; viral-load distribution; SARS-CoV-2; age
• ISSN: 0300-5771; 1464-3685
• DOI: 10.1093/ije/dyab145

Abstract Background Describing the SARS-CoV-2 viral-load distribution in different patient groups and age categories. Methods All results from first nasopharyngeal (NP) and oropharyngeal (OP) swabs from unique patients tested via SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) collected between 1 January and 1 December 2020 predominantly in the Public Health Services regions Kennemerland and Hollands Noorden, province of North Holland, the Netherlands, were included in this study. SARS-CoV-2 PCR crossing-point (Cp)-values were used to estimate viral loads. Results In total, 278 455 unique patients were tested, of whom 9.1% (n = 25.374) were SARS-CoV-2-positive. PCRs performed by Public Health Services (n = 211 914), in which sampling and inclusion were uniform, revealed a clear relation between age and SARS-CoV-2 viral load, with especially children aged <12 years showing lower viral loads than adults (β: –0.03, 95% confidence interval: –0.03 to –0.02, p < 0.001), independently of sex and/or symptom duration. Interestingly, the median Cp-values between the >79- and <12-year-old populations differed by more than four PCR cycles, suggesting an ∼16-fold difference in viral load. In addition, the proportion of children aged <12 years with a low load (Cp-value >30) was higher compared with other patients (31.1% vs 17.2%, p-value < 0.001). Conclusions In patients tested by Public Health Services, SARS-CoV-2 viral load increases with age. Further studies should elucidate whether the lower viral load in children is indeed related to their suggested limited role in SARS-CoV-2 transmission. Moreover, as rapid antigen tests are less sensitive than PCR, these results suggest that SARS-CoV-2 antigen tests have lower sensitivity in children than in adults.