you need a flu shot every year/season because (HA-haemoagglutinin; NA-neuroaminidase) A) the virus can change its HA and NA every year, so a new shot is needed to teach your immune system how to recognize the changed HA and NA B) flu virus gets rid of its HA and NA and replace them with completely new ones every year C) your immune system weakens after a year-so you have to get another shot to get the system strong enough to attack the virus D)antigen shift occurs every year

Vaccines typically contain particles that are pieces of the virus or bacteria they target. How do you think this helps you avoid getting sick in the future?  a) vaccine-preventable diseases are just part of life. it is better to have the disease than become immune through vaccines  b) vaccine programs fail to produce overall health benefits of a population by because they do not reduce the transmission od disease c) the particles act as antibodies, against which the person's immune system will develop antibodies  d) the particles act as antigens, against which the person's immune system will develop antibodies  e) vaccines create an entirely new immune system

Which of the following destroys virus-infected cells?   Question 6 options:   A)  cytotoxic T cells   B)  B cells   C)  T helper cells   D)  dendritic cells

An allergy can best be defined as ______. A) a component of the humoral response B) an exaggerated response to an allergen C) part of the normal immune response D) a type of cell-mediated adaptive immunity