the circulation of common respiratory viruses and their co-infection with severe acute respiratory syndrome coronavirus 2 before and after coronavirus disease of 2019 vaccination

Background: respiratory viruses play important roles in respiratory tract infections; they are the major cause of diseases such as the common cold, bronchiolitis, pneumonia, etc., in humans that circulate more often in the cold seasons. during the covid-19 pandemic, many strict public health measures, such as hand hygiene, the use of face masks, social distancing, and quarantines, were implemented worldwide to control the pandemic. besides controlling the covid-19 pandemic, these introduced measures might change the spread of other common respiratory viruses. moreover, with covid-19 vaccination and reducing public health protocols, the circulation of other respiratory viruses probably increases in the community. objectives: this study aims to explore changes in the circulation pattern of common respiratory viruses during the covid-19 pandemic. methods: in the present study, we evaluated the circulation of seven common respiratory viruses (influenza viruses a and b, rhinovirus, and seasonal human coronaviruses (229e, nl63, oc43, and hku1) and their co-infection with sars-cov-2 in suspected cases of covid-19 in two time periods before and after covid-19 vaccination. clinical nasopharyngeal swabs of 400 suspected cases of covid-19 were tested for sars-cov-2 and seven common respiratory viruses by reverse transcription real-time polymerase chain reaction. results: our results showed common respiratory viruses were detected only in 10% and 8% of sars-cov-2-positive samples before and after vaccination, respectively, in which there were not any significant differences between them (p-value = 0.14). moreover, commonviral respiratory infections were found only in 12% and 32% of sars-cov-2-negative specimens before and after vaccination, respectively, in which there was a significant difference between them (p-value = 0.041). conclusions: our data showed a low rate of co-infection of other respiratory viruses with sars-cov-2 at both durations, before and after covid-19 vaccination. moreover, the circulation of common respiratory viruses before the covid-19 vaccination was lower, probably due to non-pharmaceutical interventions (npi), while virus activity (especially influenza virus a) was significantly increased after covid-19 vaccination with reducing strict public health measures.