Nirmatrelvir/ ritonavir

Baseline was defined as the latest measurement between Day -1 and Day 1, but post-dose samples that were collected within 1 hour post start of dosing were also treated as baseline. Samples with result "\< lower limit of quantification (LLOQ)" were imputed as 1.7 log10 copies/milliliter (mL), and samples with result "Not Detected" were imputed as 0.0 log10 copies/mL.

NP swab was collected by healthcare professional (HCP) from participants and were sent to the central laboratory for viral RNA level testing real-time reverse transcriptase-polymerase chain reaction(RT-PCR). Sustained was defined as NP swab SARS-CoV-2 RNA level not \>=2.0 log10 per milliliter (copies/mL) at any study visit (through Day 44) following the first study visit where the participant's NP swab SARS-CoV-2 RNA level \<LLOQ (\<2.0 log10 copies/mL).

Percentage of participants who developed symptomatic Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) or Rapid Antigen Test (RAT) confirmed SARS-Cov-2 infection were reported in this outcome measure. Index case was defined as participants with symptomatic COVID-19.

Percentage of participants with COVID-19 related hospitalization or death from any cause during the first 28 days of the study was estimated using the Kaplan-Meier (KM) method. Using KM method, survival probability for each time interval was calculated as the number of participants surviving divided by the number of participants at risk. Participants who had the event, dropped out, or moved out were not counted as "at risk" i.e., participants who were lost were considered "censored" and were not counted in the denominator.

Cmax was the maximum observed plasma concentration and was directly observed from data. Concentration values below the lower limit of quantification (LLQ) were set to zero. Geometric mean analysis was on the log scale. Zero values were not included in geometric mean and geometric coefficient of variation calculation. The geometric coefficient of variation was expressed in percentage.

AUClast was area under the plasma concentration time-curve from zero (pre-dose) to the last measured concentration. The geometric coefficient of variation was expressed in percentage.

AUCinf was defined as area under the plasma concentration-time curve from time zero to infinity. The geometric coefficient of variation was expressed in percentage.

AUCinf was calculated by AUClast + (Clast/kel). AUClast was the area under the plasma concentration-time profile from time 0 to the time of Clast. Clast was the predicted plasma concentration at the last quantifiable time point estimated from the log-linear regression analysis and kel was the terminal phase rate constant calculated by a linear regression of the log-linear concentration-time curve.

Total amount of unchanged drug excreted in the urine over 48 hours.

Renal clearance was calculated as total amount of unchanged drug excreted in the urine over 48 hours (Ae48) divided by area under the plasma concentration-time profile from time 0 to 48 hours post dose.