Research has shown that sex (male vs female) as a variable contributes to differences in the safety and efficacy of drugs, biologics, and devices. Biologics include vaccines and plasma. Devices can range from drug eluting stents and pacemakers to implants and contact lenses.
To better understand the biologic basis for sex differences, women’s organizations have been advocating for the participation of women in clinical trials. Several federal offices dedicated to women’s health have also worked to ensure mandates that require inclusion of women in federally funded studies are met. Unfortunately, many privately funded researchers are not mandated to include women, though some have learned the wisdom of doing so. When both sexes are represented in preclinical (animal) and clinical (human) research, a better understanding of the mechanistic basis for disease susceptibility and response to therapy can be achieved. This is the first step to personalized medicine.
When we speak of ‘sex’, we are talking about biology, i.e., the physical characteristics that make us male or female. ‘Gender’ refers to the differences between man and women due to cultural or social variations in a particular sex (feminine vs. masculine). Both are important when we do research.
So where do we stand today? A recent Institute of Medicine report found that women were less than 40% of many research study populations. When it comes to preliminary animal research (which is used as a basis for future human studies) the data is even worse. Only 22-42% of studies published in journals on neurosciences, endocrinology, physiology, pharmacology, reproductive medicine and biology reported the sex of the experimental animals. Furthermore, even when both sexes are included, rarely do researchers report the differences in outcomes by sex. 
So what can we do? Participate in a clinical trial if you have an opportunity. If your doctor prescribes a medication or procedure that is relatively new, you might ask if the studies included women. There is an unexplained complacency among the public that research is fairly distributed among the sexes. The truth is, we still have lots to learn about women-specific health.