A pilot study evaluated the safety of Ozonized Saline Solution (O3SS) used as a complementary therapy in adult patients COVID-19


Currently, there is no effective antiviral therapy recommended for the new coronavirus disease 2019 pneumonia (COVID-19). The purpose of this pilot study was to evaluate the safety of Ozonized Saline Solution (O3SS) used as a complementary therapy in adult patients COVID-19.

Twenty-five adult patients who were hospitalized with mild to severe COVID- 19 symptoms, who met the inclusion criteria and were being treated from April 18rd to April 26th, 2020, at the Viamed Virgen De La Paloma Hospital, Madrid, Spain were included in this study.

Patients were allocated to receive standard care (SC) that included 200-400 mg hydroxychloroquine twice daily for 5-7 days plus Tocilizumab 400 mg twice daily for 5 days, low molecular weight heparin (LMWH) and 40 mg-60 mg metil-prednisone plus O3SS, 200 mL, 3-5 µg/mL daily for 10 days.

No control group was included, data were compared to clinical trials in this subject. Primary outcomes of treatment with O3SS were an improvement of clinical symptoms and a reduction in mortality.

Secondary end points evaluated included participant clinical status, laboratory examinations, and duration of viral shedding. None of the patients treated with SC + O3SS died.

Improvements in symptoms such as dyspnea, weakness, and reduction in body temperature were observed and corresponded with an improvement of laboratory finding including D-dimer, fibrinogen, LDH, and CRP.

No side effects from the O3SS treatment were observed. Conclusions: COVID-19 patients with mild to severe symptoms who received intravenous O3SS as a complementary therapy demonstrated no side effects.

This preliminary data will be served as base for a future study of the efficacy of this therapy.


A coronavirus named Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was isolated as the causative agent of severe pneumonia. This infections has been termed Coronavirus Disease 2019 (COVID-19) by the World Health Organization (WHO) who officially declared COVID-19 a pandemic on March 11, 2020 [1]. COVID-19 rapidly spread into at least 213 countries and killed more than 500,000 people by June 30, 2020. There are not specific therapies available to treat the Covid-19 infection.

Hydroxychloroquine (HCQ) and chloroquine (CQ) have garnered unprecedented attention as potential therapeutic agents against COVID-19. Apart from their antimalarial use, they have also shown an in vitro activity against COVID -19 [2]. However, there is a growing body of scientific data of their side effects particularly in QTc prolongation and cardiac arrhythmias [3].

There are multiple physiological pathway dysregulations that appear to be disrupted by the SARS-CoV-2 and related viruses. Angiotensin-converting enzyme (ACE2) has recently been identified as the SARS-CoV-2 receptor.

The ACE2 system is a critical protective pathway from inflammatory injuries due to excess oxidative stress. An unregulated ACE2 dysfunction worsens COVID-19 and could initiate multi-organ failure.

The imbalance in the action of ACE1 and ACE2-derived peptides [Angiotensin II (Ang II) and Angiotensin 1-7 (Ang 1-7), respectively] may explain most of the pathological consequences of SARS-CoV- 2 infections [4].

Health risk factors that predispose COVID-19 patients for a progression of the disease to more advanced stage include proinflammatory conditions such as hypertension, diabetes and cardiovascular disease [5].

Earlier studies of the related SARS-CoV virus infections of primates suggest that the severe lung injury was due to an exacerbated inflammatory response mediated through an activation of the innate immune system and an upregulation of the NF-κB pathway [6].

A recent human study demonstrated that in critically ill patients, the SARS-CoV-2 virus cause an exacerbated inflammatory response which is not self- limiting, it is uncontrolled generating an inflammatory cytosine storm.

This is happening because, in theory the lymphocytes NK and T cytotoxic (CD8 and CD4+) should inhibit the macrophage activity, but by down regulation this inhibition does not occur because the infected cells lack Major Histocompatibility Complex, who should inhibit the action of the macrophage.

This is caused a suppression of functional lymphocytes (lymphopenia) resulting in decreased immune function and increased susceptibility to infection [7]. Additional animal studies have demonstrated that the pulmonary fibrosis that is a hallmark of the SARS disease process is mediated through an induction of TGF-beta1 by way of an upregulation of the ROS/ p38 MAPK/ STAT3/Egr-1 pathway both in vitro and in vivo [8].

Host genetics may also play a role in pathogenesis since studies on knock-out mice have demonstrated that a genetic deficiency of ACE2 receptors resulted in a reduction of Ang 1,7 thus increasing oxidative stress and susceptibility to advanced disease progression [9].

Medical ozone (O2/O3) at a low dose which is produced by a mixture of oxygen (carrier) and ozone (active component) in a carrier of 99.9% pure oxygen. Medical ozone therapies (O3X) have been demonstrated to be effective in treating a range of human pathologies that have a physiological basis of inflammatory dysregulation (oxidative stress). Properly dosed and timed treatments have the ability to induce endogenous oxidative preconditioning [9].

Potentially, O3X may improve the symptoms of COVID-19 acting as an inductor of adaptation to OS, a modulator of pro-inflammatory cytokines and improving tissues oxygenation [10].

A preliminary case report shown the benefit of the treatment with ozone in two COVID-19 patients in China [11] also in 18 patients treated in Ibiza (Spain) as part of a single-center prospective cohort study [12].

These findings allowed us to evaluate the safety and efficacy of ozonized saline solution (O3SS) in patients with mild to severe COVID-19 as a complementary therapy. Here, we report data from 25 patients who received standard care (SC) plus O3SS.

The results suggest that O3SS as a complementary therapy accelerates the recovery of the patients, stabilizes their biochemical index, reduces the need for oxygen support and shows no side effects.

Materials and Methods

The complementary application of O3SS was done in accordance with the principles of the Declaration of Helsinki [13] and the Good Clinical Practice Guidelines of the International Conference on Harmonization [14].

All patients and/or legal representatives were informed about the objectives and risks of participation. They were given time to carefully read and sign the informed consent form. Random online clinical monitoring and quality control were performed.

A virtual independent data safety and monitoring board (DSMB), composed of O3x experts, clinicians, and experts in infectious diseases from AEPROMO (Spanish Association of Medical Professionals in Ozone Therapy) and ISCO3 (International Scientific Committee of Ozone Therapy), was selected to review the protocol and hold daily meetings to follow the daily results of the application of O3SS.

The trial was reported according to the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline [15].

The pilot study protocol was approved by the site hospital direction (fast tract) on April 17th and the full randomized clinical trial by the Regional Ethics Committee of Madrid (Number 05/20) on May 18th.

This manuscript is a partial report (pilot study) of the full study involved the comparison between two parallel groups SC alone and SC plus O3SS. Pilot study will not publicly register because data acquisition will serve to perform the full randomized clinical trial [EudraCT number, 2020-002425-28 and AEMPS number, 20-0381], that will be publicly register and performed after administrative approved, using the pilot study experience. Results will be reported in a future manuscript.

Design and Site


The complementary application of O3SS was done following the criteria of a pilot, open label, phase III clinical trial, between April 18th to April 26th 2020, aiming to first treat hospitalized patients with mild to severe respiratory syndrome secondary to SARS-CoV-2 infection COVID-19; and as a second aim, to assess the safety and efficacy of O3SS.

These patients were hospitalized at the Viamed Virgen de la Paloma Hospital, Madrid (declared COVID-19 center during the epidemic). The hospital has all source documents registered in an electronic medical recording system. Clinical analyses, laboratory examinations, and routine Chest radiographs are also available locally.


Hospitalized patients with clinical suspicion of COVID-19 (i.e., history of fever and any respiratory symptom, e.g., cough or rhinorrhea); male or female aged 18-98 years old at the time of inclusion; within 1 week of onset; who did not participate in other clinical studies within the last three months; willing and able to sign the informed consent for participation in the application of O3SS; Chest radiographs confirmed pulmonary lesions (for moderate cases); were included. Patients were enrolled before laboratory confirmation of COVID-19 by reverse transcription–polymerase chain reaction (RT-PCR Covid-19), considering that this procedure could delay inclusion. The flow chart (Fig. 1) presents clinical-epidemiologic suspected cases as well as cases already confirmed by RT-PCR Covid-19.

The exclusion criteria included: Female participants who were pregnant, lactating or planning pregnancy during the course of the trial. Patients with significant renal or hepatic impairment or with scheduled elective surgery or other procedures requiring general anesthesia during the application of O3SS.

Participants who had participated in any clinical trial involving an investigational product within the past 12 weeks prior to the study. Patients with G-6PD defect (Favism). Patients who continually used immunosuppressant, or were organ transplant recipients within the last 6 months.

Patients with history of not controlled hyperthyroidism, unstable period of severe cardiovascular disease, copper or iron supplementation via IV or any situation that did not allow the patients safety during the study. The patient had to be transferred to a non-participating hospital within 72 h. Patients receiving copper or iron supplementation i.v.

Figure 1. Study flow chart. Eligible participants were allocated to receive standard care (SC), basically: (40 mg-60 mg methyl prednisone daily for 5-7 days plus Tocilizumab 400 mg twice daily for 5 days, low molecular weight heparin (LMWH) and hydrocortisone) plus O3SS, 200 mL, 3-5 μg/mL daily for 10 days) plus ozonized saline solution (O3SS), 3-5 μg/mL daily for 10 days.

Participants were allocated at the time of inclusion and were subsequently identified throughout the application of O3SS only by their allocated number, always assigned in chronological order. This was an open label application of O3SS.

Sample Size Calculation

The sample size calculation for this pilot complementary application of O3SS was estimated according to the suggestion of Whitehead A.L. et al [16]. Medium sample (25 subjects) was selected for a future main trial designed with 90% power and two-sided 5% significance.


According to hospital protocol, all patients meeting the same criteria of the study (i.e., acute respiratory distress syndrome) received intravenous ceftriaxone (250 mg – 2 g twice daily for 7 days) plus azithromycin (500 mg once daily for 5 days), Enoxaparina (Clexane®) 40 – 60 mg daily, HCQ 200 mg, methyl prednisone 40 mg or prednisone 5 mg systematically, starting on day 0. Tocilizumab (Actemra®), 0,4 mg twice daily for 5 days, was also prescribed when influenza infection was suspected.

O3SS consists of bubbling and saturating 200 mL of sterile physiological solution (0.9%) with O2/O3 mixture during 10 min, at concentrations ranging 3-5 µg/NmL.

Keeping bubbling, using the infusion set, the solution was administered i.v. (thought the basilic brachial or cephalic veins) during (15 to 30) min.

Ozonation (bubbling) was stopped when about 50 mL of liquid remaining in the bottle [17]. Patients received SC plus O3SS.

The first 5 days the bubbling concentration used was 5 µg/NmL (total dose per day 250 µg of O3), administered daily. In the following 5 sessions, the bubbling concentration was lowered to 3 µg/NmL (total dose per day 150 µg of O3), and administered daily.

Patients received 10 sessions of O3SS in total. The concentration of ozone was measured by a build in spectrophotometer in the ozone generator (254 nm). The concentration of ozone in saline solution during the continuous bubbling flow was calculated as ¼ of the bubbling concentration [18].

Under this ozonisation condition it has been demonstrated that no H2O2 or HOCl appeared in relevant concentration (H2O2 not exceeding 0.0004 % [19] HOCL concentration are less than 0.001 g/mL [20]. The ozone decomposition processes in NaCl 0.9 % aqueous solutions is not accompanied by formation of products other than oxygen [21].

Ozone was generated by a medical class IIb CE device (Ozonobaric P®, SEDECAL®, Spain). The container that administered the solution was disposable, made of medical-grade materials, free of phthalates and fully compatible with ozone.

It had a classification as medical devise class IIb obtained from Bexozone® (Bexen medical®, Spain). Physiological Saline Solution (NaCl 0.9 %) from (Lab. ERN, Spain) was used.

Clinical parameters were measured daily by the routine clinical staff from day 0 to discharge or death, and then at day 28 for discharged patients, to assess efficacy (day 7 and

14) and safety outcomes. Laboratory parameters and electrocardiograms were performed at the clinician’s discretion. Data were recorded on the case report form and then transferred into an electronic database (Excel®, Microsoft®), which were further validated by external trial monitoring staff.

Dyspnea was scaled as: Grade 0, no dyspnea; grade 1, slight dyspnea; grade 2, moderate dyspnea; grade 3, severe dyspnea; grade 4 very severe dyspnea [22]. Weakness was scaled as: 0, paralysis; 1, severe weakness; 2, slight weakness; 3, normal strength [23].


Safety outcomes included adverse events that occurred during treatment, serious adverse events, and premature or temporary discontinuation of treatment. Adverse events were classified according to the National Cancer Institute Common Terminology Criteria for Adverse Events.

The null hypothesis was that the complementary application of O3SS in the experimental group would have a mortality rate that was 50% lower than the mortality reported for only SC by day 14. Thus, the primary end point was mortality by day 14.

Secondary end points included participant clinical status, laboratory examinations, chest radiographs on days 7 and 14, daily clinical status during hospitalization, duration of mechanical ventilation (if applicable) and supplementary oxygen (if applicable), and the time (in days) from treatment initiation to death. Here we present analyses until day 14, with lethality as the primary outcome.

Virologic measures included viral RNA detection was performed daily until 2 consecutive negative values was obtained.

To evaluate the efficacy outcome the seven-category ordinal scale was used, and consisted of the following categories: 1, not hospitalized with resumption of normal activities; 2, not hospitalized, but unable to resume normal activities; 3, hospitalized, not requiring supplemental oxygen; 4, hospitalized, requiring supplemental oxygen; 5, hospitalized, requiring nasal high-flow oxygen therapy, noninvasive mechanical ventilation, or both; 6, hospitalized, requiring extracorporeal membrane oxygenation, invasive mechanical ventilation, or both; and 7, death [24].

Disease severity was defined as: Mild, No signs of pneumonia on imaging; Moderate, Fever and respiratory symptoms with radiological findings of pneumonia; Severe Dyspnea, respiratory frequency ≥ 30/min, blood oxygen saturation ≤ 93%, PaO2/FiO2 ratio < 300, and/or lung infiltrates > 50% within 24– 48 h; Critical Respiratory failure, septic shock, and/or multiple organ dysfunction/failure [25].

Laboratory Analysis

Hematology and biochemistry analyses were performed in automatized machines. Samples (2 nasopharyngeal or 1 oropharyngeal swabs) were submitted to Novel Coronavirus (2019-nCoV) Real Time RT-PCR test, using a kit from Biopath-Unilabs (France) by Cobas z480 qPCR (Roche), with the use of LightMix Modular SARS-CoV-2 (COVID19).

Sampling did not stop when a swab at a given time point was negative. Baseline throat swabs were tested for detection of E gene, RdRp gene, and N gene, and samples on the subsequent visits were qualitatively detected for E gene.

Statistical Analysis

Descriptive statistics were used for demographic, laboratory, and clinical data. To assess the safety of the SC + O3SS compared to SC, the proportion (and 95% CI) of deaths in SC + O3SS group was compared with the historical proportion (and 95%CI) of deaths in patients who did not use O3SS in Spain and Europe in the same period [26-28].

For qualitative variables, χ2 tests and Fisher exact tests were performed. We used the t test or Mann-Whitney test to compare means and medians. The Wilcoxon signed-rank test and Hodges–Lehmann estimate was used to compare inter quantile ranges (IQR). Statistical analyses were performed in IBM SPSS statistic version 17, and a 2-tailed P < 0.05 was considered significant.


Demografic and clinical characteristics

A total of 25 patients that were allocated to the SC + O3SS group completed the study. (Fig. 1). Some patients (4 of 25 [16%]) had COVID-19 confirmed a posteriori by reverse transcription–polymerase chain reaction testing. The patients with initial unconfirmed disease who had clinical and epidemiological presentation compatible with COVID-19 were analyzed together. Overall baseline characteristics are presented in Tab. 1.

Table 1: Demographic and clinical findings of patients at baseline.1

Legend: 1. In all cases the race was white; 2. No former smoker was found; 3. Symptoms with frequency lower that 20 % n (%): cough with phlegm 4(16); central chest pain 4(16); pharyngodynia 3(12); abdominal distension 3 (12); abdominal colic 3 (12); flatulence 2(12); lateral chest pain 3(12); lower limb edema 1(4) and oliguria 1(4). COPD, chronic obstructive pulmonary disease. *, significant difference (p<0.05), χ2 tests for proportion between gender.

Baseline characteristics show an overall median (min -max) age of 44 (30 -95) years and a predominance of women (14 [65%]). The most frequent comorbidities were hypertension (4 of 25 [16%]), asthma (3 of 25 [12%]), hypothyroidism (3 of 25 [12%]), smoking (2 of 25 [8%]), and obesity (2 of 25 [8%]). Hypertension was more frequent in male vs female (4 of 11 [36%] vs 0). On admission, oxygen support was required in 14 of the 25 patients (56%), which was more frequent requirement in males vs females (10 of 11 [90%] vs 4 of 14 [28%]).

Baseline body temperature was greater than 37.5 °C in 13 of 25 patients (52%); with a greater frequency in males vs females (8 of 11 [72%] vs 5 of 14 [35%] respectively). Main presenting clinical symptoms were weakness (21 of 25 [84%]), dyspnea (19 of 25 [76%]), dry cough (14 of 25 [56%]) and anosmia (12 of 25 [48%]). Polymyalgia and headache were present more frequently in females (both 43%) than in males (27% and 18 % respectively).

Laboratory findings (Tab. 2) show borderline low levels of hemoglobin in male patients. Increased levels of serum ferritin, fibrinogen, D-dimer, LDH, CPR, ALT and AST was found in all patients. Serum ferritin values were significantly (p<0.05) higher in women as compared to men and CRP was significantly (p<0.05) higher in men as compared to women. All patients were positive for qualitative SARS-CoV-2 PCR at baseline.

Table 2: Laboratory and radiographic findings of patients at baseline.

Legend: 1. Viral RNA SARS-CoV-2 load in throat swabs sample; 2. Value according to seven-category ordinal scale; ALT, Alanine aminotransferase; AST, Aspartate aminotransferase; GGOI, Ground-glass opacity infiltration; LDH, Lactate dehydrogenase; NR, Normal Range; CRP, C-reactive protein; ↑ above the reference range; ↓ below the reference range; disease severity was done according the criteria of Chinese Center for Disease Control and Prevention [25]. No significant difference (p>0.05), χ2 tests was found between data expressed as proportion; *, significant difference (p>0.05) between gender within the same series.

The most common radiographic finding on a chest radiograph was ground-glass opacity infiltration (Tab. 2), in 40 % of patients and pleural effusion in 20 %. Pulmonary auscultation found rales, rales/rhonchi and wheezing sound in 56 % of the patients. A majority of patients fit the severe disease status (76%) and 6 (24%) meet the criterium of mild disease.

Clinical outcomes

Overall mortality rate in our group patients was zero. Safety outcomes were evaluated at 7 and 14 days. Haematological and laboratory findings did not undergo notable modification with the application of O3SS therapy.

No decrease in haemoglobin levels, or increased in LDH, ALT or AST compared to baseline were found. No side effects associated with the investigational drug (O3SS) were detected.

Occurrence of epistaxis was detected in 3 patients between days 3-4 of treatment with a suspension of heparin reversing the symptoms. Progressive reduction of body temperature was observed in patient with >37.5 °C at baseline (Fig. 2a). From the day 3 a significant (p<0.05) reduction was found, at day 8, all patients return to values of body temperature lover than 37.5 °C.

Figure 2: Change from baseline in: (a) body temperature (percent from baseline and – – trendline), error bars indicate 95% confidence intervals. * significant difference (p<0.05), χ2 tests was found between data expressed as proportion, compared to baseline value; (b) Dyspnea and weakness. For Dyspnea [22] and Weakness [23] score, see Material and Method; * significant difference (p<0.05) compared to baseline value within the same series. (c) Change from baseline in C-reactive protein (CRP) * significant difference (p<0.05) compared to baseline, values within the normal range (<10 mg/L). Error bars indicate 95% confidence intervals.

Dyspnea and weakness was gradually reduced (Fig. 2b). From day 7 dyspnea prevalence was reduced by 40 % (slight dyspnea) on day 14, only 1 patient (4 %) remained with this symptom.

Weakness was improved on day 7 when 86 % of the patients passed from severe weakness to slight weakness. On day 14, 91 % of patients shifted from severe weakness to slight weakness. The CRP values (Fig. 2c) entered into the normal range within 24 h of the first application of the O3SS.

Serum ferritin, fibrinogen, D-dimer and LDH were progressively decreasing during the treatment (Fig. 3a). By day 10, fibrinogen and LDH values entered the normal ranges in all patients. ALT and AST were also decreased during this time and by the day 10 remained above the normal range in 7 of 25 patients (28%) and 9 of 25 patients (36%), respectively.

The rate of decline in activity of ALT and AST by day 10 were 82±117 U/L and 71±65 U/L, respectively.

Average duration of viral shedding was 8 days (IQR 6.0-11.5). None of the 25 patients withdrew throughout the application of O3SS. The average duration of hospitalization from inclusion to discharge was 14 days (IQR 9.5-15) (Tab. 3).

Efficacy outcome based on the seven-category ordinal scale shows at day 7 an improvement in 19 out of 25 patients (76%). Out of these 19 patients, 17 patients (68%) shifted from 5 to 3 and 2 patients (8%) shifted from 4 to 2 on the ordinal scale.

By the end of the treatment with O3SS (day 14) most of the patients (18 out of 25 [72%]) were in score 2 (discharge), (6 out of 25 [24%]) in score 3 (hospitalized, not requiring supplemental oxygen), and (1 out of 25 [4%]) was admitted to the intensive care unit (ICU).

Figure 3: Follow-up of biochemical findings. (a) Serum ferritin; (b) Fibrinogen; (c) D-Dimer;
(c) LDH. Values represented a mean ± S.E.M. The baseline and follow-up values correspond to patients with biochemical index out of normal range that complete the three-point test: for serum ferritin, n=18; fibrinogen, n=10; D-dimer, n=10; LDH, n=20. *, significant differences (p < 0.05) compared to day 1; **, significant difference (p< 0.05) compared to day 1 and 6.

Table 3: Efficacy outcomes.

Legend: ECMO, extracorporeal membrane oxygenation; HFNC, high-flow nasal cannula for oxygen therapy; IQR, interquartile range; SC + O3SS, standard care (SC) plus ozonized saline solution (O3SS).


The COVID-19 pandemic represents a global public health crisis. Given the severity with which this disease has unfolded, empirical treatment recommendations for COVID-19 are being made based on unpowered studies.

Because of the mortality and morbidity associated with the disease untested drugs with a questionable safety profile at higher doses are being prescribed on a compassionate basis [29].

For facing this pandemic, the repurposing of existing therapeutic agents happens to be the only pragmatical approach as urgent response, as most of these drugs have already been tested for their safety [30].

These agents can be classified into two categories:

1) Agents that directly target the virus replication cycle, and

2) Agents based on immunotherapy approaches.

“The development of vaccine represents a more long-term strategy to prevent COVID-19 outbreaks in the future” [30]. O3x has been used to treat different pathologies including viral diseases [17].

There are well known different mechanisms that presuppose the utility of O3x in COVID-19 infection [10]. In this indication, O3x can be classified as immunomodulator, either boosting innate antiviral immune responses or alleviating damage induced by dysregulated inflammatory responses.

The population distribution by age in this complementary application of O3SS (30-50 years [28%], 50-70 years [52%] and >70 years [20%]) was in line with the international epidemiologic data reported for this infection [31] and infected Spain population [26,27].

This finding emphasises that subjects of any age can acquire COVID-19 infection. However, adults of middle age and older are most commonly affected. The average age ranged in Spain was 18 – 102 years [26] similar with the average age of our patients 55 (30-95).

In others studies of hospitalized patients with confirmed COVID-19, the average ranged from 49 to 56 years [32,33]. Comorbidities have been associated with severe illnesses and mortality, however the results of application of O3SS indicates that only (9 of 25 [36%]) patients did not show comorbidities.

The most frequently comorbidities were hypertension, asthma, hypothyroidism, smoking and obesity, in line with the data available from infected patients in Spain [26,27]. Except hypothyroidism, all other conditions are considered risk factors for SARS-CoV-2 infection [34].

All patients were white, therefore an analysis of differences between races was not performed. In general, more males were affected by the disease as reported in cohorts studies from China, Italy, and the United States [35-37].

However, we enrolled more women (14), than men (11), but an analysis of the ratio of gender incidence in this case is not valid, because the small number of subjects. In addition, in a study performed in Madrid in 2226 case, was found e relative more proportion of affected female patients (51.8 %) [27].

Fever (defined as an axillary temperature over 37.5°C) is not a universal finding on presentation of COVID-19. In our sample (13 of 25 [52%]) had fever at baseline (Tab. 1). In a study of over 5000 patients who were hospitalized with COVID-19 in New York, only 31% had a temperature >38°C at presentation [35].

In another study of 1099 patients from Wuhan and other areas in China, fever was present in only 44% on admission but was ultimately noted in 89% during the hospitalization [38]. In an epidemiological study in 18 European hospitals in 1420 patients’ fever was appeared in 45.5 % of the subjects [28].

Nevertheless, our patients treated with O3SS (Fig. 2a) had their febrility reduced gradually in line with their favorable recovery. Nevertheless, our patients treated with O3SS (Fig. 2a) fever reduced gradually in line with their favorable recovery.

All clinical manifestations found in patients (Tab. 1) were similar to the clinical features of the disease onset [39]. The main clinical manifestations of disease (dyspnea and weakness) had a favorable course of resolution in O3SS treated patients. On days 7 and 8 respectively (Fig. 2b) these symptoms were found to be significantly (p<0.05) improved.

Acute respiratory distress syndrome (ARDS) is the major complication of patients with severe disease. ARDS was shown in 20%, on average of 8 days after the onset of symptoms in a study involved 138 COVID-19 patients; in this study mechanical ventilation was implemented in 12.3% [39].

In addition, some patients with initially no severe symptoms may progress over the course of a time (in a week). In another study, the median time to dyspnea was 8 days [33]. However, without exceptions, our 25 patients after the treatment with O3SS, had a resolution of the dyspnea.

Elevation of inflammatory markers (e.g., ferritin, D-dimer, CPR), were observed in our COVID-19 patients, in line with the results of other recent reports [40] and epidemiological report form Madrid in the same period [26].

Elevated ferritin has also emerged as poor prognostic factors. Higher serum ferritin was associated with ARDS development [41], in addition ferritin was raised in 72.4 % of patients in a study involved 6 424 subjects in Madrid [26].

In addition, higher D-dimer was detected in 36% of patients in a descriptive study of 99 COVID-19 cases in Wuhan, China [32] but lower form the values reported in Madrid in the same period (61.5%) [26].

The higher levels of D-dimer were significantly associated with increased risk of ARDS [42]. Increased disease severity and ARDS development were associated with elevated CRP [40]. According to different studies from China and Singapore, mean values of CPR in patients that did not require supplemental O2 were 11.1 (IQR: 0.9-19.1 mg/L); in patients that required O2, 65.6 (IQR: 47.5-97.5 mg/L) [43] and in the mortality group, 109.25, (IQR 35.00-170.28 mg/L) [44]. In our patients, in correspondence with their clinic improvement, the average baseline values of CPR were 12.5 (IQR: 2.5-19.3 mg/L) after the first 24-48 h (Fig. 2c).

Fibrinogen was also higher in our sample, confirming that the hypercoagulation in patients with SARS-CoV-2 represent an important complication. Higher level of D-dimer, and fibrinogen was found in a clinical study, in COVID-19 patients, as compared with healthy controls (p<0.001) [45].

In addition, high LDH level was significantly associated with severe COVID-19 on admission [46]. In our findings administration of O3SS reduced the levels of inflammatory markers (e.g., ferritin, D-dimer, CPR, LDH) and fibrinogen as marker of coagulation function (Fig. 3).

Radiographic findings and auscultation revealed signs of pneumonia in 60 and 56 % of patient respectively (Tab. 2) similar to the results reported from COVID-19 patients in Madrid in the same period, in which rales were present in 52.4% [26].

Chest radiographs may be normal in early or mild disease. In a retrospective study of 64 patients in Hong Kong with documented COVID-19, 20 % did not have any abnormalities on chest radiograph at any point during the illness [47].

Main abnormal radiograph findings were consolidation and ground glass opacities, with bilateral, peripheral, and lower lung zone distributions [48]. The 25 patients treated with O3SS, bilateral signs of pneumonia were present only in 24-32% of them, according to the radiographic findings or auscultation, respectively (Tab. 2).

Normally lung involvement increased over the course of illness, with a peak in severity at 10 to 12 days after symptom onset [49]. However, in our patients, chest radiographs and auscultation drastically changed after the third to fifth session of O3SS, with both showing an improvement of their status.

Time from inclusion to discharge in patients treated with O3SS and SC was not significantly different (>0.05) as compared to other report of patients treated only with SC in Madrid in the same period (mean 10 days, range 1-62 d) [26].

However, the inclusion of O3SS as a complementary treatment, accelerated the improvement of patients in terms of clinical symptoms (Tab. 3) and laboratory biomarkers (Fig. 2).

This improvement avoided the patient transit to critical status. In addition, the time to median duration of viral shedding [8 days (IQR 6.0-11.5)] and longest duration of viral shedding (22 days) were reduced compared to other reports of 20.0 days (IQR 17.0-24.0) and 37 days, respectively [50]. Non death was recorded during the study at time 7 or 14 d. However, mortality rate in hospitalized COVIS-19 patients in Madrid in the same period was 20.7-21.1% [26,27].

The most probable mechanism associated to the low doses of ozone, using physiological saline solution as a carrier and applied as a complementary therapy in COVID-19 patients, will be thought the modulation of the “cytokines storm” through the balanced regulation of the Nrf2/NF-κB pathway[10]. The potential benefit of ozone in these clinical condition’s merits further research. Clinical study with this rational are already propose [51].


Results of this pilot study suggest that patients with mild to severe symptoms due to COVID- 19 disease by the inclusion of O3SS treatment as a complementary therapy to standard care was safe. No side effects were observed during the O3SS treatment.

The use of O3x as adjuvant treatment for the management of the infection by SARS-CoV-2 patients has molecular and preclinical scientific evidence and clinical justification in term of cryoprotection and control of the inflammatory response. Based on the results of this clinical trial, it would be reasonable to conduct further clinical studies with this therapy on other viral diseases with a similar clinical and pathophysiological profile. Without a sufficiently powered randomized controlled trial, application of O3SS cannot be recommended for COVID-19 or other viral infections.

Conflicts of Interest

The funders had no role in the design of the protocol applied to the patients; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Gregorio Martínez-Sánchez is the President of ISCO3 (International Scientific Committee of Ozone Therapy), Adriana Schwartz is the secretary of the ISCO and the president of AEPROMO (Spanish Association of Medical Professionals in Ozone Therapy). This study was partially funded by AEPROMO.

Funding Statement

This complementary application of O3SS was funded by AEPROMO and partially by SESMI (Spanish Society of Health and Integrative Medicine); SEDECAL S.A. (Spanish Society of Electromedicine and Quality) lent the ozone devices and donated consumables.


To all members of AEPROMO for their contribution. For their assistance in data collection: Clara Barrachina and Fabricio Quintero. For corrections to the English style and wording: Roberto Quintero, Ana Gutiérrez Gossweiler and Michel Gossweiler. For the technical support: José Ramos.


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