Seroprevalence of SARS-CoV-2 antibodies and associated risk factors in children less than 6 years of age in the canton of Fribourg, Switzerland (COVPED study): a population-based cross-sectional study

Abstract

BACKGROUND: To date, few data are available about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in young children and the role of early-life childcare arrangements in transmission of the virus. In this study, we assessed the SARS-CoV-2 seroprevalence in children less than 6 years of age in the canton of Fribourg and identified risk factors associated with seropositivity. METHODS: The COVPED study is a population-based cross-sectional study in children less than 6 years of age living in the canton of Fribourg, Switzerland, who presented to a private paediatrician or the paediatric emergency department of the Fribourg Hospital during a 9-week period between 11 January and 14 March 2021. Immunoglobulin G antibodies against SARS-CoV-2 trimeric spike protein were measured in capillary blood samples using an in-house Luminex assay. A mean fluorescence intensity ratio of above 6 was considered as positive. Metadata was collected through electronic questionnaires. Logistic regression analysis was performed to assess the risk of seropositivity and associated factors. RESULTS: A total of 871 children, with a median age of 33 months (range 6 days to 5 years 11 months) were included; 412 (47%) were female. Overall, 180 (21%, 95% confidence interval [CI] 18–24%) children were seropositive. Age as continuous variable was not associated with seropositivity risk, apart from a higher rate in children less than 3 months of age. Univariable analysis showed that female sex was associated with a lower seropositivity risk (unadjusted odds ratio [OR] 0.69, 95% CI 0.49–0.96; p = 0.03). Day-care attendance was also associated with a lower seropositivity risk (OR 0.67, 95% CI 0.47–0.95; p = 0.03), whereas all other childcare arrangements were not associated with seropositivity. No association was found between the number of children and adults present in extra-familial care and seropositivity. Multivariable analysis identified the number of household members above the age of 12 years being positive for SARS-CoV-2 as the main risk factor for seropositivity in children (adjusted odds ratio [aOR] 7.80, 95% CI 4.65–13.07; p <0.001 for one household member, aOR 22.07, 95% CI 13.49–36.11; p <0.001 for two household members and aOR 32.20, 95% CI 9.30–111.55; p <0.001 for three or more household members). CONCLUSION: The number of household members tested positive for SARS-CoV-2 (PCR test) is the main exposure risk to seropositivity for children less than 6 years of age. But the family size is not associated with an increased risk of infection. In young children, extra-familial care does not increase the risk of becoming SARS-CoV-2 seropositive, neither does the number of contacts present in extra-familial care. As adults and children will be vaccinated and new virus variants will be circulating the risk of exposure for young children will likely change and needs further monitoring.

SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during the pre- and omicron-dominant wave, from January 2021 through December 2022, Thailand: A longitudinal study

“…Although an increased number of household members did not affect the risk of seropositivity in children, we found that a higher risk of seropositivity was observed in children living with infected household members than those living with non-infected household members. This finding was consistent with a study from Switzerland that indicated the risk of being seropositive in children aged <6 years was more likely associated with the number of household members who tested positive for SARS-CoV-2, indicating the SARS-CoV-2 transmission for children aged <6 years occurs commonly within the family [ 20 ]. In addition, our study was consistent with previous reports in Uganda that reported no significant difference in infection-induced seropositivity based on the gender of the study participants [ 11 ].…”

Estimated relative potential for airborne SARS-CoV-2 transmission in a day care centre

“…However, recent studies have shown that the continuation of the epidemic with new SARS-CoV-2 variants and shifts in preventive measures and vaccination changed the situation [ [88] , [89] , [90] , [91] ]. In addition, it seems that transmission between family members seemed more important than transmission within day care centres [ 87 , 92 ].…”

SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during pre- and omicron-dominant wave, from January 2021 through November 2022, Thailand: Longitudinal study

“…seropositive in children aged <6 years was more likely associated with the number of household members who tested positive for SARS-CoV-2, indicating the SARS-CoV-2 transmission for children aged <6 years occurs commonly within the family[15].The proportion of anti-N IgG or anti-RBD antibody seropositive among unvaccinated and anti-N IgG seropositive among vaccinated cases may reflect the true rate of infections, including mildly symptomatic or asymptomatic cases and undetected by COVID-19 testing. Our study found that 35.9% children aged 5-7 years with seropositivity reported no previous infection.This result may reflect either asymptomatic infection or undetected infection upon COVID-19…”