The Bacillus Calmette-Guérin (BCG) vaccine is the only vaccine used to provide protection against the infectious bacterial disease tuberculosis (TB). Most countries of the world have a BCG vaccination programme. Countries are classified by the World Bank into one of four income groups. Table 3.1 shows the estimated incidence of TB for 2012 to 2016 for these income groups. The incidence represents the number of new cases of TB occurring per 100000 people in one year. The new cases include the number of cases that have occurred again after a period of recovery (relapse TB).

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

1. [1] Mycobacterium tuberculosis; A Mycobacterium bovis
2. [1] any one from live in an area that has cases of TB; recently returned from countries with TB ; born in a country with TB ; parents / grandparents whose origin country has TB ; contact with a person who has TB ; AVP; e.g. ref. to compromised immune system mother who is HIV-positive
3. [3] any three from decrease in incidence over time for all groups or decrease in incidence over time for low, lower middle, upper middle and plateau for high income group ; one example of, large / AW, differences in incidence; e.g. between, upper middle income and, low / lower middle between high income and, low / lower middle / low and lower middle; between upper middle and high ; decrease in incidence with income group increase (for each year), generally / overall / except for 2015/2016 low to lower middle; low and lower middle similar incidence; data / manipulated data, to support any of above points;
4. [2] any two from max 1 if no ref. to antigens leprosy bacterium has similar (shaped) antigens ; memory cells, recognise / bind, antigens on leprosy bacterium ; anti-TB antibodies also bind to leprosy antigens ; AVP; e.g. similar / same, genes so synthesise similar proteins
5. [3] any three from artificial active natural passive deliberate / AW or not deliberate / from mother/in breast milk / across placenta ; A from medical staff vaccine / (foreign) antigens in injection or antibodies passed on; immune response or no immune response; antibodies / memory cells produced or no, antibodies / memory cells produced ; longer lasting or short-lived; protection not immediate or immediate protection ;