UPSC Prelims 2010 · General Studies

Question 21: Science and Technology

Widespread resistance of malarial parasite to drugs like chloroquine has prompted attempts to develop a malarial vaccine to combat malaria. Why is it difficult to develop an effective malaria vaccine ?

aMalaria is caused by several species of Plasmodium

bMan does not develop immunity to malaria during natural infection

cVaccines can be developed only against bacteria

dMan is only an intermediate host and not the definitive host

AnswerThe answer is (b).

In natural malaria infection the body builds only partial, short-lived protection, so there is no strong natural immunity for a vaccine to copy, unlike measles where infection leaves lasting immunity. On top of this, the parasite has a complex life cycle and changes its surface proteins, which makes vaccine design hard. Several Plasmodium species cause malaria, but a vaccine can be aimed at the deadliest one, so that alone is not the difficulty. Remember: vaccines usually mimic the protection that natural infection leaves, and malaria leaves little.

Why each option is right or wrong

(a) Several species exist, but a vaccine can target one such as Plasmodium falciparum; this is not the main obstacle.
(b) Right (as keyed): infection leaves little lasting protection, so there is no natural immunity to copy.
(c) Wrong: vaccines exist against viruses too, such as measles and polio.
(d) Man is the intermediate host and the mosquito the definitive host, but that fact does not block vaccine development.

Worth knowing: Option (a) is also a real difficulty and natural infection does leave partial immunity, so the wording of (b) is loose and the key is open to dispute.

Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious question Next question

Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.