Background
Immunity is the ability of an organism to resist infection.
Passive Immunity
-outside source providing antibodies.
-short lived because body doesn't replace them once they are broken down, as body doesnt produce them.
Active Immunity
-stimulated production of antibodies by immune system.
-long lasting.
A vaccination is the introduction of a pathogen (usually weakened/attenuated) into the body with the intention of stimulating active immunity against that pathogen.
Passive Immunity
-outside source providing antibodies.
-short lived because body doesn't replace them once they are broken down, as body doesnt produce them.
Active Immunity
-stimulated production of antibodies by immune system.
-long lasting.
A vaccination is the introduction of a pathogen (usually weakened/attenuated) into the body with the intention of stimulating active immunity against that pathogen.
A Successful Vaccination Program:
-economically available in enough bulk to immunise all vulnerable population.
-few side effects (unpleasant side effects deter people, so herd immunity is harder to achieve).
-ability to produce, transport and store vaccine in a safe hygienic way (e.g. refrigerated lorry).
-skilled staff to administer vaccine at many places throughout the area.
-ability to create herd immunity, usually by vaccinating the vulnerable population all at once in order to interrupt the transmission of the pathogen.
-few side effects (unpleasant side effects deter people, so herd immunity is harder to achieve).
-ability to produce, transport and store vaccine in a safe hygienic way (e.g. refrigerated lorry).
-skilled staff to administer vaccine at many places throughout the area.
-ability to create herd immunity, usually by vaccinating the vulnerable population all at once in order to interrupt the transmission of the pathogen.
Does Vaccination Eliminate Disease?
No. Even if you do all of the above, it is extremely difficult to eliminate the disease because:
-some people have defective immune systems so vaccines don't work (e.g. from HIV)
-an individual may develop the disease immediately after vaccination (before they are immune).
-a pathogens antigens can suddenly mutate (antigenic variability) so you are only immune to one strain.
-certain pathogens can 'hide' in calls or in the intestines (e.g. cholera) where the immune system can't reach.
-some people refuse to have vaccines for religious, medical or ethical reasons (e.g. MMR vaccine was temporarily linked to autism).
-some people have defective immune systems so vaccines don't work (e.g. from HIV)
-an individual may develop the disease immediately after vaccination (before they are immune).
-a pathogens antigens can suddenly mutate (antigenic variability) so you are only immune to one strain.
-certain pathogens can 'hide' in calls or in the intestines (e.g. cholera) where the immune system can't reach.
-some people refuse to have vaccines for religious, medical or ethical reasons (e.g. MMR vaccine was temporarily linked to autism).
Problems with Cholera Vaccine
-cholera is an intestinal disease, so immune system does not go there.
-treatment is often useless as bacteria is flushed out by diarrhoea (a symptom).
-cholera has a high antigenic variability (antigens are regularly mutating).
-cholera thrives in crowded, transient (mobile) populations so it is hard to know who has been vaccinated out of the vulnerable residents.
-cholera thrives in poor areas (damp, unhygienic, crowded) so vaccine may not be economically available.
-treatment is often useless as bacteria is flushed out by diarrhoea (a symptom).
-cholera has a high antigenic variability (antigens are regularly mutating).
-cholera thrives in crowded, transient (mobile) populations so it is hard to know who has been vaccinated out of the vulnerable residents.
-cholera thrives in poor areas (damp, unhygienic, crowded) so vaccine may not be economically available.
Problems with TB Vaccine
-increased spread of HIV so more people with defected immune systems (more likely to contract TB)
-poverty, wars and political unrest means many refugees who are forced to live in crowded, damp conditions (TB thrives here).
-the disease has spread world wide (by global trade, tourism and refugees) so is impossible to know who has had a vaccination.
-aging population (they often have weaker immune systems so a vaccine may not stimulate enough immunity).
-poverty, wars and political unrest means many refugees who are forced to live in crowded, damp conditions (TB thrives here).
-the disease has spread world wide (by global trade, tourism and refugees) so is impossible to know who has had a vaccination.
-aging population (they often have weaker immune systems so a vaccine may not stimulate enough immunity).
Questions
1) Whats the difference between passive and active immunity? (2 marks)
2) Explain why vaccinating against influenza is not always effective. (5 marks)
3) Why is it difficult to control TB by vaccination? (4 marks)
2) Explain why vaccinating against influenza is not always effective. (5 marks)
3) Why is it difficult to control TB by vaccination? (4 marks)