The COVID-19 global pandemic is accelerating investigations for effective vaccines and repurposable validated therapeutics. Current data analyses strongly suggest that the disease mostly affects the elderly population and patients with pre-existing conditions [1,2]. Considerably less attention has been drawn towards the sex distribution of case fatalities, which is increasingly showing disparities in mortality rates that varies geospatially, and along socioeconomic factors [3,4]. Reported death estimates by sex vary greatly across contexts and population groups and may change over time. In addition, social factors, such as testing and reporting bias in females, or differences in exposure due to behavioral and risk differences, may play a role, e.g., due to comorbidities such as diabetes or differences in societal and gender norms. While the observed male dominance in COVID-19 prevalence and mortality across most countries and cultures may suggest a role for biological differences, the potential long-term impact of gender-related factors on mortality, especially in diverse socioeconomic contextS, cannot be underestimated [5,6].
The role of immunological differences between females and males in the responses to SARS-CoV-2 infection appears to be justified. There is ample evidence that antiviral immunity differs between the sexes [5]. These are caused by e.g., sex steroid hormone signaling (i.e., testosterone, estrogens, and progesterone), genetics (e.g., immune function genes that escape X inactivation), and sex-specific composition of the microbiome. Sex differences in immunosenescence and immune function not only impact immunity to viruses, but to vaccines and immunotherapies, as well [5,6,7]. In the context of SARS-CoV-2, these differences could impact susceptibility and initial response to the virus as well as choice of acute and long-term therapy of the COVID-19 pathology. In current and future trials for COVID-19, sex as a biological variable should be factored in and understood, along with the wider gendered implications of the COVID-19 crises, with the broader concept of how biological factors intersect with gendered differences in exposure, transmission, and socio-economic means. Consequently, the pandemic may not just lead to differences in disease susceptibility and manifestation between men, women, and people with non-binary identities, but also exacerbate unequal access to treatment and long-term vulnerabilities.
Given their non-negligible impact on health, sex and gender dimensions, along with other socio-economic stratifiers, need to inform the design, conduct, analysis, and reporting of current and forthcoming trials. Moving beyond sex-disaggregated data collection and including variables such as disability, age, ethnicity, migration status, socioeconomic status, or geographic location, will contribute to ensure health benefits from clinical trials for all. To better understand and respond to the burden posed by COVID-19, both on health systems and different segments of human populations, gender dimensions must be recognized as an intersecting component of wider structural inequalities [8]. Moreover, the COVID-19 pandemic is exposing, most acutely, the wider social inequalities that are based on gendered social, cultural, and economic faultiness, whether it is leaving a majority of frontline workers (in many contexts mostly women) without PPE, the disproportionate burden of unpaid care on women, or gender-based violence perpetuated within the household, apart from the economic devastations experienced by the poor and women in the poorest quintiles.
Equity in clinical trials starts with the consideration of both sex and gender dimensions in studies on novel and repurposed drugs [9,10]. Biomedical AI-researchers can assist in this effort to reconceptualize the human subgroups included for analysis, emphasizing the rigorous justification of exclusion and avoiding assumptions that may have serious implications in terms of generalizability of outcomes [9,11,12]. Ignoring aspects of sex and gender in data collection and analysis in clinical trials has had detrimental consequences in the past. Eight out of ten drugs withdrawn from the US market in the late 1990s had significantly more side effects in women than men, including fatal torsade-de-pointe after excessive QT interval prolongation. The, yet to be accurately tested, proposed therapeutic regimen of hydroxychloroquine and azithromycin for COVID-19 includes two QT-prolonging agents. Next to potential sex differences in side effects, gender-related aspects have to be considered. For example, despite the disproportionately high mortality of Ebola viral disease (EVD) among pregnant women, the rVSV-ZEBOV vaccine clinical trials excluded pregnant women. This impacted access to critical life-saving interventions during the subsequent Tenth EVD epidemic in DRC, when—due to lack of evidence because of the beforementioned exclusions—pregnant and lactating women did not partake in ring vaccination campaigns, until the decision was reversed 10 months later. This not only led to unnecessary mortality of this vulnerable group, but severely impacted women’s right to decide on research participation and community trust in the intervention, just as did the approval of Truvada solely for cisgender males and transgender women [13,14].
The inclusion of sex and gender aspects in drug development and clinical trials is essential, not just for a thorough understanding of efficacy and safety aspects of drugs, but also to ensure there is equity in the distribution of innovation and discovery benefits of COVID-19 therapeutics and vaccines [3]. A group of clinicians, scientists and gender specialists working on global health, sex and gender research and human rights are thus calling for action towards the inclusion of sex and gender, and other socially relevant variables, into the methodology of COVID-19-related trials. Such an approach should become a universal and manifest part of future clinical studies, to allow more personalized patient care and contribute to universal health coverage.
Acknowledgments
We would especially like to thank Sulzhan Bali (Women in Global Health), Susan Bell (Drexel University), Chandani Kharel (HERD International), for their tremendous contribution to the manuscript. We would like to thank the entire Gender and COVID-19 Working Group for their thoughts, inputs and ongoing scientific support.
Appendix A
Appendix A.1. The Sex and Gender in COVID-19 Clinical Trials Working Group
| Evelyne Bischof | Shanghai University |
| Sabine Oertelt-Prigione | Radboud University Medical Center |
| Rosemary Morgan | Johns Hopkins Bloomberg School of Public Health |
| Sabra Klein | John Hopkins Bloomberg School of Public Health |
| Clare Wenham | London School of Economics and Political Science (LSE) |
| Nazneen Damji | UN Women |
| Alison ROWE | UN Women |
| Laura Mamo | San Francisco State University lmamo@sfsu.edu |
| Sulzhan Bali | Women in Global Health sulzhan@gmail.com |
| Susan E. Bell | Drexel University seb376@drexel.edu |
| Ann Keeling | Women in Global Health |
| Chandani Kharel | HERD International |
| Ilana Löwy | CERMES 3, (INSERM, CNRS, EHESS, Paris V) |
| Anna Coates | Panamerican Health Organization |
| Shirin Heidari | GENDRO’s Health |
| Petra Verdonk | Amsterdam UMC-VUmc |
| Arne Ruckert | University of Ottawa |
| Luisa Enria | University of Bath |
| Shelley Lees | London School of Hygiene and Tropical Medicine (LHTM) |
| Amber Peterman | University of North Carolina |
| Sean Hillier | York University |
Appendix A.2. Gender and COVID-19 Working Group
| Clare Wenham | London School of Economics |
| Rosemary Morgan | John Hopkins University |
| Julia Smith | Simon Fraser University |
| Evelyne Bischof | Shanghai University of Medicine and Health Sciences, Federico II University, Napoli, Italy, and Women’s Brain Project |
| Sabra Klein | John Hopkins University |
| Madeline Johnson | Global Affairs Canada |
| Chris Berzins | Global Affairs Canada |
| Sulzhan Bali | Women in Global Health |
| Karen Grepin | University of Hong Kong |
| Susan Mackay | GAVI |
| Denise Nacif Pimenta | Oswaldo Cruz Foundation |
| Niyati Shah | USAID |
| Kelly Thompson | independent consultant |
| Sabine Oertelt-Prigione | Radboud University |
| Amber Peterman | University of North Carolina and UNICEF Innocenti |
| Ruth Kutalek | Medizinischen Universität Wien |
| Sophie Harman | QMUL |
| Ilana Lowy | French National Centre for Scientific Research |
| Nazeen Damji | UN Women |
| Ann Keeling | Women in Global Health |
| Kate Hawkins | Pamoja Communications |
| Myra Betron | Jhpiego |
| Susan Bell | Drexel University |
| Manasee Mishra | IIHMR University, India |
| Sean Hillier | York University |
| Yara M. Asi | University of Central Florida |
| Shelley Lees | London School of Hygiene and Tropical Medicine |
| Alan White | Leeds Beckett University |
| Nigel Mxolisi Landa | Great Zimbabwe University |
| Pavitra Kotini-Shah | University of Illinois at Chicago |
| Megan O’Donnell | Center for Global Development |
| Jelke Boesten | King’s College London |
| Goleen Samari | Columbia University |
| Alexa Yakubovich | University of Toronto |
| Liana R Woskie | Harvard Global Health Institute |
| Peter Baker | Global Action on Men’s Health |
| Camila Pimentel | Oswaldo Cruz Foundation/Aggeu Magalhães Institute |
| Derek M. Griffith | Vanderbilt University |
| Sara Davies | Griffith University |
| Elena Marbán-Castro | Barcelona Institute for Global Health |
| Claudia Abreu Lopes | United Nations University, International Institute for Global Health |
Author Contributions
Conceptualization and methodology, E.B., S.O.-P., S.L.K. and R.M.; writing—original draft preparation E.B., S.O.-P., S.L.K., writing—review and editing, E.B., S.O.-P., S.L.K. and R.M., project administration, R.M. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Conflicts of Interest
The authors declare no conflict of interest.
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