The masters think a slave who chooses to work during his time off doesn't deserve the time off, and a slave who doesn't work to save enough throughout the year to buy whiskey for the holidays is considered lazy.
An adjuvant is a substance added to some vaccines to enhance the immune response of vaccinated individuals. The aluminum salts in some U.S. licensed vaccines are aluminum hydroxide, aluminum phosphate, alum (potassium aluminum sulfate), or mixed aluminum salts.
Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection by any natural or wild pathogen), or therapeutic (e.g., vaccines against cancer are also being investigated). The administration of vaccines is called vaccination. The effectiveness of vaccination has been widely studied and verified; for example, the influenza vaccine, the HPV vaccine, and the chicken pox vaccine.