The current novel coronavirus disease 2019 (COVID-19) pandemic is revealing profound differences between men and women in disease outcomes worldwide. In the United States, there has been inconsistent reporting and analyses of male-female differences in COVID-19 cases, hospitalizations, and deaths. We seek to raise awareness about the male-biased severe outcomes from COVID-19, highlighting the mechanistic differences including in the expression and activity of angiotensin-converting enzyme 2 (ACE2) as well as in antiviral immunity. We also highlight how sex differences in comorbidities, which can be associated with both age and race, impact male-biased outcomes from COVID-19. We are in the midst of a pandemic. Many of us predicted that the next "100 year pandemic" would be caused by an influenza A virus, like the H1N1 virus that caused the 1918 influenza pandemic. Instead, the current pandemic is caused by a novel β-coronavirus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). Currently, there are almost 2 million cases and over 100,000 deaths worldwide from the disease caused by this virus, called the novel coronavirus disease 2019 (COVID-19). Like the 1918 influenza pandemic [1], men are at greater risk of more severe COVID-19 outcomes than women, with both sex (i.e., biological differences) and gender (i.e., sociocultural and behavioral differences) playing fundamental roles. The initial reports from China, followed by data from several countries in Europe, have highlighted that there are roughly similar numbers of confirmed SARS-CoV2 cases between men and women. The severity of COVID-19, as measured by hospitalization, admission to intensive care units, and rates of fatality, however, has consistently been 2-fold greater for men than women [2], with the Global Health 50/50 research initiative providing real-time sex-disaggregated data from most countries worldwide [3]. Unfortunately, despite the United States currently having the most COVID-19 cases in the world, considerably less attention has been paid to sex-disaggregation of data than in Europe and China. We took this opportunity to evaluate the current situation in the US to both determine if similar patterns of male-female differences are observed and to document which states are or

Vaccine-induced immunity declines with age, which may differ between males and females. Using human sera collected before and 21 days after receipt of the monovalent A/Cal/09 H1N1 vaccine, we evaluated cytokine and antibody responses in adult (18–45 years) and aged (65+ years) individuals. After vaccination, adult females developed greater IL-6 and antibody responses than either adult males or aged females, with female antibody responses being positively associated with concentrations of estradiol. To test whether protection against influenza virus challenge was greater in females than males, we primed and boosted adult (8–10 weeks) and aged (68–70 weeks) male and female mice with an inactivated A/Cal/09 H1N1 vaccine or no vaccine and challenged with a drift variant A/Cal/09 virus. As compared with unvaccinated mice, vaccinated adult, but not aged, mice experienced less morbidity and better pulmonary viral clearance following challenge, regardless of sex. Vaccinated adult female mice developed antibody responses that were of greater quantity and quality and more protective than vaccinated adult males. Sex differences in vaccine efficacy diminished with age in mice. To determine the role of sex steroids in vaccine-induced immune responses, adult mice were gonadectomized and hormones (estradiol in females and testosterone in males) were replaced in subsets of animals before vaccination. Vaccine-induced antibody responses were increased in females by estradiol and decreased in males by testosterone. The benefit of elevated estradiol on antibody responses and protection against influenza in females is diminished with age in both mice and humans.

Swine influenza virus (SwIV) is one of the important zoonotic pathogens. Current flu vaccines have failed to provide cross-protection against evolving viruses in the field. Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable FDA approved polymer and widely used in drug and vaccine delivery. In this study, inactivated SwIV H1N2 antigens (KAg) encapsulated in PLGA nanoparticles (PLGA-KAg) were prepared, which were spherical in shape with 200 to 300nm diameter, and induced maturation of antigen presenting cells in vitro. Pigs vaccinated twice with PLGA-KAg via intranasal route showed increased antigen specific lymphocyte proliferation and enhanced the frequency of T-helper/memory and cytotoxic T cells (CTLs) in peripheral blood mononuclear cells (PBMCs). In PLGA-KAg vaccinated and heterologous SwIV H1N1 challenged pigs, clinical flu symptoms were absent, while the control pigs had fever for four days. Grossly and microscopically, reduced lung pathology and viral antigenic mass in the lung sections with clearance of infectious challenge virus in most of the PLGA-KAg vaccinated pig lung airways were observed. Immunologically, PLGA-KAg vaccine irrespective of not significantly boosting the mucosal antibody response, it augmented the frequency of IFN-γ secreting total T cells, T-helper and CTLs against both H1N2 and H1N1 SwIV. In summary, inactivated influenza virus delivered through PLGA-NPs reduced the clinical disease and induced cross-protective cell-mediated immune response in a pig model. Our data confirmed the utility of a pig model for intranasal particulate flu vaccine delivery platform to control flu in humans.

Men experience more severe outcomes from coronavirus disease 2019 (COVID-19) than women. Golden Syrian hamsters were used to explore sex differences in the pathogenesis of a human clinical isolate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).