Discussion
To the best of our knowledge, this study is the first to investigate the associations of personal and seasonal factors with IgG levels to RSV and RV viruses in a large population of children and adults. Results showed that an older age was associated with higher RV-specific IgG levels in children (aged between 2-16 years) and lower RV-specific IgG level in adults (aged between 18-79 years) while it was associated with higher RSV-specific level in both children and adults. RV-specific IgG levels were higher in women and lower with higher BMI both in children and adults, while RSV-specific IgG levels were not associated with sex and BMI. Higher levels of RSV and RV-specific IgG were found during winter, spring and autumn in adults while no significant association with season was observed for children. Current smoking, and to a lesser extent former smoking, were associated with higher IgG levels for RSV and all RV species in adults whereas passive smoking among children was not associated with RSV and RV-specific IgG levels. Overall, these results suggest that different determinants might influence the immune response to respiratory viruses, according to the respiratory virus (RSV or RV) and the age (in children or in adults).