Missing microbes in infants and children in the COVID-19 pandemic:a study of 1,126 participants in Beijing,China

The COVID-19 pandemic has caused many fatalities worldwide and continues to affect the health of the recovered patients in the form of long-COVID.In this study,we compared the gut microbiome of uninfected infants and children before the pandemic began(BEFORE cohort,n=906)to that of after the pandemic(AFTER cohort,n=220)to examine the potential impact of social distancing and life habit changes on infant/children gut microbiome.Based on 16S rRNA sequencing,we found a significant change in microbiome composition after the pandemic,with Bacteroides enterotype increasing to 35.45%from 30.46%before the pandemic.qPCR quantification indicated that the bacterial loads of seven keystone taxa decreased by 91.69%–19.58%.Quantitative microbiome profiling,used to enhance the resolution in detecting microbiome differences,revealed a greater explained variance of pandemic on microbiome compared to gender,as well as a significant decrease in bacterial loads in 15 of the 20 major genera.The random forest age-predictor indicated the gut microbiomes were less mature in the after-pandemic cohort than in the before-pandemic cohort in the children group(3–12 years old)and had features of a significantly younger age(average of 1.86 years).Lastly,body weight and height were significantly lower in the after-pandemic cohort than in the before-pandemic cohort in infants(<1 year of age),which was associated with a decrease in bacterial loads in the fecal microbiome.