Table 1. . A summary of available studies on sex and COVID-19 outcomes.
| Source (year) | Study design | Country | Sample size (n =) | Defined comparator | COVID-19 outcome | Findings | Limitations | Ref. |
|---|---|---|---|---|---|---|---|---|
| Baden et al. (2020) | Randomized, observer blinded, placebo-controlled trial | USA | 30,420 | Males vs females | Vaccine efficacy | Vaccine efficacy was similar in males vs females | Short duration of efficacy | [19] |
| Bignucolo et al. (2021) | Meta-analysis | Global | >30,000 (multiple studies) | Males vs females | Vaccine efficacy | Higher odds of vaccine being efficacious in males compared with females | End point timelines differed between studies | [20] |
| Fortunato et al. (2021) | Retrospective epidemiological | Italy | 55,131 | Males vs females | Hospitalization rates, viral clearance, mortality | Males had increased hospitalization rates and mortality | Lifestyle, behavioral and social differences not assessed | [17] |
| Gomez et al. (2021) | Retrospective cohort | USA | 8108 | Males vs females | Hospitalization, ICU admission, endotracheal intubation, mortality | Males had higher rates of hospitalization and ICU transfers | Single health system, early on data from pandemic | [16] |
| Gupta et al. (2020) | Multicenter retrospective cohort | USA | 2215 | Males vs females | 28-day in-hospital mortality | Males had increased odds of 28-day mortality | Baseline risks may have differed between patients of different hospitals | [8] |
| Hur et al. (2020) | Retrospective observational | USA | 486 | Males vs females | Predictors of intubation in COVID-19 patients | Male sex, age and several other factors predictive of intubation | Intubation criteria differ among providers | [21] |
| Klang et al. (2020) | Retrospective observational | USA | 6760 | Males vs females | Age, comorbidities (cardiovascular, renal), mortality in those who passed from COVID-19 | Males had increased mortality but similar cardiovascular disease profiles; female age was higher than males for those who passed | Urban population, observational study | [22] |
| Moiseev et al. (2020) | Retrospective cohort | Russia | 1522 | Males vs females | Requirement for mechanical ventilation and mortality rates in the ICU | Under 50 years of age, males had increased ventilation requirements but similar mortality; over 50 years, males had greater mortality rates | Specific subgroup studied (those in ICU on ventilatory support – fairly high overall mortality rate compared with general population) | [23] |
| Moula et al. (2020) | Meta-analysis | Global | 8497 | Males vs females | Mortality risk | Males had 16% higher mortality risk | Increased heterogeneity in primary end points between papers | [6] |
| Nepogodiev et al. (2020) | Retrospective case control | Global | 1128 | Males vs females | 30-day postoperative mortality in patients with COVID | Males had increased odds of postoperative 30-day mortality | Some patients included based on clinical diagnosis; all types of surgeries included | [7] |
| Nguyen et al. (2021) | Multicenter retrospective observational | USA | 308, 010 | Males vs females | In-hospital mortality, length of hospital stay, intubation rates | Males had high odds of hospital mortality, length of hospital stay and intubation rates | Vizient database may have inaccurate coding | [24] |
| Peckham et al. (2021) | Meta-analysis | Global | 3,111,714 | Males vs females | ICU admission and death | Males have three-times odds of requiring ICU admission and increased odds of death | Data on comorbidities such as age, ethnicity and comorbidities not present | [5] |
| Polack et al. (2020) | Placebo-controlled, observer-blinded efficacy trial | Global | 43,548 | Males vs females | Vaccine efficacy | Vaccine efficacy was similar between males and females | Short follow-up times | [25] |
| Quaresima et al. (2021) | Retrospective | Italy | 1000 | Males vs females | Hospitalization age, latency between symptom onset and hospitalization | No differences found between age of hospitalization and latency of hospitalization | Reference center hospital for severe illnesses include hematologic, renal and neurological issues | [18] |
| Raparelli et al. (2020) | Retrospective observational | Italy | 3517 | Males vs females | Comorbidities (ischemic heart disease, chronic kidney disease), dementia, autoimmune diseases) in those who passed from COVID-19 | Increased odds for males to experience ischemic heart disease compared with females for those who passed from COVID-19 | Only deceased individuals included with unclear baseline comorbidity severity | [26] |
| Toth-Manikowski et al. (2021) | Retrospective cohort | USA | 4407 | Males vs females | 28-day in-hospital mortality, acute kidney injury and respiratory failure within 14 days of ICU admission | Males had increased risk of mortality, severe acute kidney injury and respiratory failure | Immune system response/sex hormone data not ascertained; USA only; acute kidney injury and respiratory failure information only acquired within first 14 days | [10] |
| Vassilaki et al. (2021) | Prospective cohort | Greece | 1643 | Males vs females | IgG antibody responses to Pfizer vaccine | Females had 1.2-fold higher antibody response | Comorbidities not controlled for; duration of antibody responses followed for short time period | [27] |
| Xu et al. (2020) | Retrospective cohort | China | 659 | Males vs females | Characteristics of ARDS patients with COVID-19, artificial intelligence model for predicting ARDS | Males had increased risk for ARDS progression | Limited ARDS data, no CT scan imaging for corroboration of diagnosis | [28] |
ARDS: Acute respiratory distress syndrome; ICU: Intensive care unit.