Although covid-19 is a new and emerging disease, it could be one of the best understood in terms of its sex-disaggregated outcomes.  This may sound surprising. Sex-disaggregated data (separated for women and men) for confirmed covid-19 cases and deaths are lacking from approximately half of the most severely affected countries, and the vast majority of countries are not reporting metrics such as sex and pregnancy status as routine for covid-19 test results, treatment, vaccine trials, or deaths. But even the fact that some countries are considering sex as an important factor in covid-19 outcomes is a significant improvement when compared to the norm of non-sex-disaggregated data collection for other infectious and chronic diseases.
Current Covid-19 mortality and morbidity data show that women are faring better than men in terms of severity of disease course, likelihood of hospitalisation and risk of death.  This sex difference can be seen across nations and socioeconomic groups, while case numbers are similar for men and women. Researchers in China reported a death rate of 2.8% among men compared to 1.7% among women, while a more recent Chinese study saw a male death rate of nearly 2.5 times that of women. [3,4] A similar picture was observed in Italy, where 70% of mortalities have been male.  However, the biological mechanisms and social factors contributing to these differences between women and men remain unclear.
Collecting sex-disaggregated data has both immediate and long-term benefits.  With clinical practice around covid-19 being continually reviewed and updated, data from the disease’s onset in late 2019 has rapidly improved the quality of care. This could be further refined by sex-disaggregated data collection, which may help our understanding of how sex hormones contribute to different female and male immunological responses. Women’s comparably favourable immune response to covid-19 might offer essential insights into treatment and vaccine development. Moreover, steroids and other immunomodulators are being trialed to manage fibrotic damage secondary to covid-19, and these drugs have different side effects in women and men.  This is one of many important considerations for clinical guidelines on management of covid-19, suggesting that attempts to standardise care should vary according to sex.
However, a distinction is necessary between sex-disaggregated data on outcomes as opposed to exposures. While countries may be making headway collecting sex-disaggregated data for covid-19 in the former category, much less reliable data are available for the latter. It is clear—though not well quantified—that women face higher risks of exposure to covid-19 than men. The majority—70%—of workers in healthcare and social sectors globally are women, which drives disparities in exposure to, and transmission of, the disease.  Increased exposure to the virus has been exacerbated by widespread reports in the NHS and internationally of unsuitable and unsafe working conditions.  Available personal protective equipment (PPE) is not designed to fit female workers, and small-sized reusable masks now being rolled out are used up before larger sizes, yet stock ordering has not accounted for this. [10,11]
Data is also missing on the indirect consequences covid-19 has had on women, both physically and sociologically. Women’s control over their work environment has been undermined as the pandemic has damaged sectors which disproportionately employ women, such as hospitality, retail, leisure as well as healthcare. The risk pregnant women face from the disease is not fully understood, and pregnant NHS workers have reported mixed responses from NHS trusts. Some occupational health departments have been over-cautious, and even paternalistic, in undermining the Royal College of Obstetrics and Gynaecology’s guidance that in the first and second trimesters pregnant doctors and nurses should assess for themselves the extent to which they are comfortable with a patient-facing role.  Meanwhile other employers have overstepped, sometimes acting illegally, by furloughing pregnant workers without discussion and then not paying their usual salary, despite contractual obligations. [13,14]
Changes to women’s work, both now and following the acute phase of the pandemic, will have lasting implications for their financial and professional status. Women are more likely than men to be primary caregivers to children and the elderly (on average, women are responsible for 60% more unpaid care work than men, which in turn limits time for paid employment).  While many professional carers and teachers have been unable to work during lockdown, women’s unpaid workloads have significantly increased due to their expanded involvement in homeschooling and care provision. But women are not being credited for this added labour. 45% of US fathers with children under 12 believed that they spent more time homeschooling than their female partners, while only 3 percent of women agreed with this assessment.  The Institute for Fiscal Studies and University College London found that mothers were able to do just one hour of uninterrupted work, for every three hours done by fathers.  To take the sphere of academia as an example, women are posting fewer preprints, submitting fewer papers for review and launching fewer research projects compared to their male colleagues during lockdown. 
That women are being forced to do an even longer “second shift” at home on top of their formal employment risks indirect harm to their long-term health. Reports from China from early in the pandemic show that prevalence and severity of depressive, anxious, and posttraumatic symptoms in women are higher than in men.  Early data also shows women are experiencing reduction in food budgets and reduced exercise opportunities compared to before lockdown. For some, the home poses an added risk, as rates of domestic abuse against women have increased in the last 3 months, with higher levels of violence leading to hospitalisation in the UK, and a doubling of partners dying as a result of domestic violence since lockdown began. 
It is important to acknowledge that the impact of covid-19 and responses to it are not shaped by sex alone; many women face further dangers. Data on race and ethnicity suggest that women from ethnic minorities have a magnified risk of being exposed to covid-19, as well as the race-related risk of a more severe disease course. The reasons why people from ethnic minority populations are more likely than white people to die from covid is currently unclear, which makes it all the more important that ongoing data collection ensure the intersection between race and sex is fully captured. 
When it comes to testing treatments and vaccines against covid-19, women are likely to suffer differentially, again. Women, particularly those who are pregnant, are routinely excluded from clinical drug trials as their anatomy and physiology are considered “distorting,” allegedly making trials more complicated to run and results harder to analyse.  However, for a potenitally fatal disease like covid-19, remaining ignorant to the sex-specific dangers that such treatments and vaccines pose, and the different levels of efficacy they may have in women, is inexcusable. Ongoing randomized controlled trials of vaccines and potentially mitigating pharmaceuticals must include representative numbers of women and men.
Most arguments for collecting sex-disaggregated data focus on the harm done to women’s health when data assumes maleness as the default. However, efforts to legislate against sexual discrimination in the US (a problem faced mostly by women), were furthered famously by Ruth Bader Ginsburg in 1975 when she argued against a provision in the Social Security Act that denied benefits to widowed fathers, while affording such benefits to widowed mothers. Bader Ginsburg’s case garnered attention because as things stood, men lost out. Similarly, in the case of direct outcomes of covid-19 where men appear to be at a disadvantage, data that takes sex into account are seen as urgent, essential and feasible by researchers, businesses and governments alike. Like Bader Ginsburg’s example, could we see strides being taken towards ensuring sex-disaggregated data collection after covid-19, because, once again, maleness confers a disadvantage?
While it is regrettable that men’s health seems to carry more weight than that of women when it comes to changing research cultures, we must ensure this pandemic is the necessary event to insist upon the collection of sex-disaggregated data as standard. Without this, any analysis is dangerously partial. To achieve better health outcomes for all, wider considerations of protection, exposures, management, treatment, clinical outcomes and consequences—which in the case of Covid-19, as with many diseases, disadvantage women and men, but in different ways—must be analysed on the basis of sex.
Katherine Ripullone, The George Institute for Global Health, University of Oxford, Oxford, UK; Cambridge University Hospitals, NHS East of England, Cambridge, UK.
Kate Womersley, The George Institute for Global Health, University of Oxford, Oxford, UK; NHS Lothian, University of Edinburgh, UK.
Sanne A.E. Peters, The George Institute for Global Health, University of Oxford, Oxford, UK; Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands.
Mark Woodward, The George Institute for Global Health, University of Oxford, Oxford, UK; The George Institute for Global Health, University of New South Wales, Sydney, New South Wales, Australia; Department of Epidemiology, Johns Hopkins University, Baltimore MD, USA.
Competing interests: None declared.
1] We recognise there is a difference between ‘sex’ and ‘gender’, and that one may be more appropriate than the other in a given context. For simplicity, we are using ‘sex’ throughout to refer to both ‘sex’ in the biological and gender in the sociological sense.
6] Caroline Criado Perez, Invisible Women: Exposing Data Bias in a World Designed for Men (Chatto & Windus, 2019).
14] Author Ripullone sits on the BMA JDC (Junior Doctors Committee), where pay for pregnant doctors has been a recurrent issue raised with the union
19] Liu N, Zhang F, Wei C, et al. Prevalence and predictors of PTSS during COVID-19 outbreak in China hardest-hit areas: gender differences matter. Psychiatry Res. 2020;287:112921.