Male and female adolescents (13–17 years, both inclusive) and children (5–12 years, both inclusive) with a clinical diagnosis of a viral AURTI were enrolled in the trial. Diagnosis by the GP was based on 1) an axillary temperature of more than 37.0°C and 2) presence of one or more of the following symptoms with onset of the first symptom within 24 hours before screening: nasal congestion, cough, sore throat, headache, fatigue, and sleep disturbance. Patients with clinical symptoms of severe flu or AURTI requiring hospitalization, or with symptoms similar to AURTI but related to other underlying diseases (infectious diseases, flu-like syndrome in systemic connective tissue disease, onco-hematologic, and other diseases) were excluded. Other exclusion criteria focused on past or current use of medications or medical disorders that could potentially confound trial results or interfere with safe completion of the trial.

Adolescents and children presenting to a GP practice with symptoms suggestive of viral AURTIs were clinically examined (including measurement of axillary temperature) by the GP on day 1 and, if eligible, were enrolled and randomly assigned (1:1) to receive active treatment or placebo in a double-blinded fashion. Patients in the active group (Group 1) received standard symptomatic therapy + Aviron Rapid, patients in the placebo group (Group 2) received standard symptomatic therapy + placebo.

Randomization of patients was done using software designed by an external, independent vendor and was stratified by center. The active and placebo treatments were packed in blisters and delivered to the GP practices in white paper boxes, labeled with unique treatment codes. Manufacturing, packaging, and labeling were performed by the sponsor of the trial. Patients, GPs, and the sponsor’s project team were blinded to treatment group assignments throughout the trial and until database lock.

On day 1, patients or their parents were given a diary to record axillary temperature, antipyretics intake, symptom severity, and recovery status twice daily with 12-hour intervals (once in the morning, once in the evening) during the treatment period, i.e., days 1 to 5 for adolescents and days 1 to 7 for children. Adolescents recorded data in the diary under supervision of their parents. For children, data was recorded by the parents. After the end of treatment, on day 6 (adolescents) or day 8 (children), patients returned to the GP practice for a closing visit. During this visit, the GP clinically examined (including measurement of axillary temperature) the patient and verified completeness of the data recorded in the diary. In addition, on day 1, symptom severity was assessed and on day 6, a general evaluation of the patient’s condition (recorded as ‘healthy’ or ‘ill’) was performed.

Aviron Rapid was provided as 647-mg tablets for oral use containing 10 mg andrographolide, 100 mg proprietary spirulina extract, and 250 mg proprietary humic acid racemic mixture. Placebo was provided as tablets visually matching the Aviron Rapid tablets. Patients were treated according to the following schedule: adolescents: 3 tablets 3 times daily on day 1, 2 tablets 3 times daily on day 2, and 1 tablet 3 times daily on days 3 to 5; children: 2 tablets 3 times daily on day 1 and 1 tablet 3 times daily on days 2 to 7. Tablets were taken with water, in the morning, at noon, and in the evening. Standard symptomatic therapy included non-steroidal anti-inflammatory drugs, decongestants, bronchodilators, mucolytics, antitussives, and other drugs for treatment of chronic diseases. Use of other antiviral remedies, antihistamines, antibiotics, and interferons was not allowed.

The primary endpoints of this trial were the number (and percentage) of clinically recovered patients and the mean disease duration. Patients were considered clinically recovered if the following 3 criteria were met: 1) persistent improvement of every symptom to “very mild” or “lack of symptoms” (severity score <2 as measured on a visual analogue scale [VAS] for adolescents or a modified face pain scale [FPS-R] for children) until the end of follow-up and a total severity score for all symptoms [i.e. the sum of the 6 individual symptom severity scores] <12 points; 2) persistent decrease of the axillary temperature to <37.0°C, i.e. temperature <37.0°C at 2 consecutive measurements with a 12-hour interval and no new increase >37°C (i.e., fever) until the end of follow-up; 3) the decrease in axillary temperature <37°C was achieved without the use of antipyretics. The severity of the symptoms nasal congestion, cough, sore throat, headache, fatigue, and sleep disturbance was measured using a VAS (for adolescents) or FPS-R (for children) ranging from 0 to 10 with 0 = lack of symptoms and 10 = very severe symptoms. Disease duration was defined as the interval between treatment initiation and the time point at which the patient met the criteria for clinically recovery. The primary endpoints were assessed twice daily with 12-hour intervals during the treatment period (days 1 to 5 for adolescents or days 1 to 7 for children) and recorded in the patient’s diary.

Secondary efficacy endpoints included number (and percentage) of patients with persistent decrease of the axillary temperature <37.0°C without the use of antipyretics, mean time to persistent decrease of the axillary temperature <37.0°C, number (and percentage) of patients taking antipyretics, mean duration of antipyretic treatment, mean total severity score for all symptoms, number (and percentage) of patients with persistent improvement of a particular symptom (severity score <2), and number (and percentage) of patients considered fully recovered. Patients were considered fully recovered if at 2 consecutive measurements with a 12-hour interval they scored 2 or 3 on a scale ranging from 1 to 3 with 1 = I still feel ill; 2 = I feel better; 3 = I feel healthy. Secondary efficacy endpoints were assessed twice daily at 12-hour intervals and recorded in the patient’s diary from day 1 to the end of treatment (day 5 [adolescents] or day 7 [children]) for axillary temperature, antipyretics intake, and symptom-related endpoints, and from day 1 to the closing visit (day 6 [adolescents] or day 8 [children]) for full recovery status.

Safety-related endpoints included the incidence of adverse events (AEs), as recorded in the patient’s diary during the treatment period, and physical examinations by the GP on days 1 and 6 (adolescents) or 8 (children).

The statistical analyses were done by an external blinded statistician. In both cohorts, a total number of 320 patients (160 per treatment group) were required to detect a difference of 5% between the two treatment groups with 80% power.

All patients who completed the treatment and all planned trial visits per protocol and did not have protocol deviations were included in the efficacy analyses. For the primary endpoint analysis, the 2-proportion Z-test was used to compare the percentages of clinically recovered patients between the active and placebo group. The mean disease duration in both groups was compared using an independent samples t-test. The secondary endpoints were analyzed using the same statistical methods as used for the primary endpoint analyses.

The safety analysis included all patients who received at least one dose of Aviron Rapid or a placebo. The incidence of AEs was summarized descriptively. All statistical tests were two-sided except for the 2-proportion Z-test. Statistical significance was set at p<0.05. All statistical analyses were performed using SPSS 17.

The trial started on 27 January 2020 (i.e., enrolment of the first patient in the trial) and was completed on 14 March 2020 (i.e., end of follow-up for the last patient in the trial). In total, 380 adolescents and 401 children were enrolled in the respective cohorts and randomly assigned to one of the two treatment groups. Safety analyses included all randomized patients. Efficacy analyses comprised 329 adolescents and 319 children. The reasons for excluding patients from the efficacy analysis are shown in Fig. 1.

Overall, in the adolescent cohort, the mean age was 14.6 years and 54% of patients were male. In the pediatric cohort, the mean age was 8.6 years and 51% of patients were male. Patient demographics were comparable in the two treatment groups in both cohorts. The total symptom severity score at baseline was slightly higher in the adolescent cohort (25.6 and 24.9 in the active and placebo group, respectively) compared with the pediatric cohort (24.6 and 23.5, respectively). The mean axillary temperature was 38°C in the active and placebo groups in both cohorts. The percentages of patients reporting any symptom at baseline were generally lower in the pediatric cohort, compared with the adolescent cohort. Nasal congestion was the most common symptom in both cohorts (reported in >91% of adolescents and >88% of children). There were no significant differences between the active and placebo group in both cohorts (Table 1).

For nasal congestion, cough, sore throat, headache, fatigue, and sleep disturbance, n (%) refers to the number (and percentage) of patients with a particular symptom at baseline; the mean values refer to the mean severity of a particular symptom at baseline.

In the adolescent cohort, the percentages of patients meeting the criteria for clinical recovery were consistently higher in the active group compared with the placebo group from 24 hours after initiation of treatment (i.e., morning of day 2: 8.1% versus 1.9%, respectively; p=0.0055) until the end of treatment (i.e., evening of day 5: 90.7% versus 80.9%; p=0.0052). Differences were statistically significant (p<0.05) as of the morning of day 2 onwards until end of treatment, except for the morning of day 4 (p=0.0786) (Fig. 2) (Supplementary Table 1) (see Appendix). The mean disease duration was significantly lower in the active group (75 h, 95% CI: 70.80, 79.20) compared with the placebo group (85 h, 95% CI: 80.90, 89.10) (p=0.003) (Fig. 3).

Similar results were obtained in the pediatric cohort with consistently higher percentages of clinically recovered patients in the active group compared with the placebo group from 24 hours after initiation of treatment (i.e., morning of day 2: 5.6% versus 4.4%, respectively; p=0.31) until end of treatment (i.e., evening of day 7: 98.8% versus 89.2%; p=0.001). Differences were statistically significant (p<0.05) as of the morning of day 3 and throughout the treatment period (Fig. 2) (Supplementary Table 1) (see Appendix). The mean disease duration was significantly lower in the active group (85 h, 95% CI: 79.50, 90.50) compared with the placebo group (101 h, 95% CI: 94.40, 107.60) (p=0.003) (Fig. 3).

Persistent decrease of temperature

From the morning of day 2 onwards until the end of treatment, the percentage of patients in the adolescent and pediatric cohorts with a persistent temperature decrease of <37°C was consistently higher in the active group than that in the placebo group, with the biggest difference between the two treatment groups being noticed on the morning of day 5 in adolescents (90.7% versus 77.7%; p<0.001) and on the evening of day 3 in children (58.4% versus 38.6%; p=0.001) (Fig. 4) (Supplementary Table 2) (see Appendix). In both cohorts, the mean time to persistent decrease of temperature was significantly lower in the active group compared with the placebo group (65 h, 95% CI: 60.80, 69.20 vs. 74 h, 95% CI: 69.30, 78.70 in adolescents [p=0.005] and 48 h, 95% CI: 42.50, 53.50 vs. 72 h, 95% CI: 65.80, 78.20 in children [p=0.001]) (Fig. 5).

The percentage of adolescent patients taking antipyretics was consistently lower in the active group compared with the placebo group from the evening of day 1 onwards until the end of treatment. In the pediatric cohort, statistically significantly lower percentages of patients on antipyretics were observed as of the morning of day 3 until the end of treatment (Fig. 6) (Supplementary Table 3) (see Appendix). The mean duration of antipyretics intake was significantly lower in the active group compared with the placebo group, both in the adolescent cohort (50 h, 95% CI: 45.90, 54.10 vs. 58 h, 95% CI: 53.60, 62.30; p=0.007) and in the pediatric cohort (43 h, 95% CI: 39.40, 46.60 vs. 62 h, 95% CI: 56.00, 68.00; p<0.001) (Fig. 7).

The mean total severity of clinical symptoms in the adolescents in the active group was consistently lower than that in the placebo group from the evening of day 1 until the end of treatment, with day 3 showing the biggest difference between the two groups (Supplementary Table 4) (see Appendix). For nasal congestion, cough, and sleep disturbance, the percentages of adolescents with persistent improvement were consistently higher in the active group compared with the placebo group throughout the entire treatment period. As of the morning of day 2 until the end of treatment, a higher percentage of patients in the active group had persistent improvement of sore throat compared with the placebo group. No relevant differences between the two groups were observed for headache and fatigue (Supplementary Tables 5–10) (see Appendix).

Among children in the active group, the mean total severity of clinical symptoms was consistently lower than that of the placebo group as of the morning of day 3 until the end of treatment. Before that time point, the mean total score was higher in the placebo group (Supplementary Table 4) (see Appendix). A similar pattern was observed for the individual symptoms nasal of congestion and cough, for which statistically significantly higher percentages of children with persistent improvement in the active group were only observed from day 5 (for nasal congestion) or day 6 (for cough) onwards. For fatigue, sore throat, and sleep disturbance, the percentages of children with persistent improvement were consistently higher in the active group compared with the placebo group as of the evening of day 1 or the morning of day 2 and throughout the entire treatment period. The largest difference between the two groups was observed on days 3 and 4 for fatigue and sleep disturbance, and on days 4 and 5 for sore throat. For headache, similar percentages were observed in both groups throughout the treatment period until the morning of day 6. As of the evening of day 6 until the end of treatment, significantly higher percentages of patients in the active group had persistent improvement of headache compared with the placebo group (Supplementary Tables 5–10) (see Appendix).

The percentage of adolescents and children being considered fully recovered was consistently higher in the active group as of the evening of day 2 or the evening of day 1, respectively, until nearly all patients in both groups reached full recovery by the end of treatment (Supplementary Table 11) (see Appendix).

In both cohorts, the incidence of AEs was similar in the active and placebo groups. No serious AEs were reported. In the adolescent cohort, 14 (7.3%) patients in the active group and 23 (12.2%) in the placebo group reported AEs, the most common being antibiotic treatment for unknown reason (reported in 13 [6.8%] and 17 [9.0%] patients, respectively). In the pediatric cohort, 30 (14.8%) and 27 (13.6%) patients in the active and placebo group, respectively, reported AEs, the most common also being antibiotic treatment for unknown reason (in 20 [9.9%] and 18 [9.1%] patients, respectively) (Table 2). Only one child in the placebo group experienced an AE of allergic reaction, and one adolescent (in the active group) and four children (2 in each treatment group) were hospitalized. No clinically relevant findings were reported for physical examinations.