inclusion criteria (applicable for both the main population and population with rebound): * participants aged 12 years or older and weighing ≥40 kg at screening. * immunocompromised * ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. participants for the main population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or other acceptable test method in any specimen collected within 5 days prior to randomization for the main study population. participants form the rebound population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or rapid antigen testing in any specimen collected within 24h prior to randomization and collected within 14 days after the completion of the initial 5-day treatment course of nirmatrelvir/ritonavir for the population with rebound.

inclusion criteria (applicable for both the main population and population with rebound): * participants aged 12 years or older and weighing ≥40 kg at screening. * immunocompromised * ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. participants for the main population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or other acceptable test method in any specimen collected within 5 days prior to randomization for the main study population. participants form the rebound population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or rapid antigen testing in any specimen collected within 24h prior to randomization and collected within 14 days after the completion of the initial 5-day treatment course of nirmatrelvir/ritonavir for the population with rebound.

inclusion criteria (applicable for both the main population and population with rebound): participants aged 12 years or older and weighing ≥40 kg at screening. immunocompromised ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. participants for the main population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or other acceptable test method in any specimen collected within 5 days prior to randomization for the main study population. participants form the rebound population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or rapid antigen testing in any specimen collected within 24h prior to randomization and collected within 14 days after the completion of the initial 5-day treatment course of nirmatrelvir/ritonavir for the population with rebound.

inclusion criteria (applicable for both the main population and population with rebound): participants aged 12 years or older and weighing ≥40 kg at screening. immunocompromised ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. participants for the main population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or other acceptable test method in any specimen collected within 5 days prior to randomization for the main study population. participants form the rebound population must have: - confirmed sars-cov-2 infection as determined by rt-pcr or rapid antigen testing in any specimen collected within 24h prior to randomization and collected within 14 days after the completion of the initial 5-day treatment course of nirmatrelvir/ritonavir for the population with rebound.

inclusion criteria: participants aged 12 years or older and weighing ≥40 kg at screening. confirmed sars-cov-2 infection immunocompromised ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. in addition, the following inclusion criteria only apply to the additional population with rebound: - presenting with documented, symptomatic, covid-19 rebound within 14 days following completion of an initial 5-day treatment course with nirmatrelvir/ritonavir

inclusion criteria: participants aged 12 years or older and weighing ≥40 kg at screening. confirmed sars-cov-2 infection immunocompromised ≥1 signs/symptoms attributable to covid-19 present on the day of randomization. in addition, the following inclusion criteria only apply to the additional population with rebound: - presenting with documented, symptomatic, covid-19 rebound within 14 days following completion of an initial 5-day treatment course with nirmatrelvir/ritonavir

inclusion criteria: confirmed sars-cov-2 infection immunocompromised onset of signs/symptoms attributable to the current covid-19 infection within 5 days prior to screening and ≥1 signs/symptoms attributable to covid-19 present on the day of randomization.

inclusion criteria: confirmed sars-cov-2 infection immunocompromised onset of signs/symptoms attributable to the current covid-19 infection within 5 days prior to screening and ≥1 signs/symptoms attributable to covid-19 present on the day of randomization.