UPSC Prelims 2010 Q21: Science & Technology – Health & Diseases
- (a) Malaria is caused by several species of Plasmodium
- (b) Man does not develop immunity to malaria during natural infection
- (c) Vaccines can be developed only against bacteria
- (d) Man is only an intermediate host and not the definitive host
Answer: (b) Man does not develop immunity to malaria during natural infection
Explanation
Why an effective malaria vaccine is hard to develop
Malaria presents unique biological challenges that complicate vaccine development, unlike many other infectious diseases.
| Option | Verdict | Reason |
|---|---|---|
| (a) Caused by several species of Plasmodium | Incorrect | While true, this is not the main reason vaccine development is specifically difficult; it's a secondary complication |
| (b) Man does not develop immunity during natural infection | Correct | Unlike many diseases where natural infection builds lasting immunity, malaria's parasite evades and suppresses the immune response, so repeated infections don't reliably confer protection — making it hard to mimic this with a vaccine |
| (c) Vaccines can only be developed against bacteria | Incorrect | This is factually false; vaccines exist against viruses and other pathogens too, not just bacteria |
| (d) Man is only an intermediate host, not the definitive host | Incorrect | While true of malaria's biology (the mosquito is the definitive host), this is not the primary reason vaccine development is so challenging |
Why malaria vaccines are hard to make:
| Point | Detail |
|---|---|
| Core challenge | Natural infection doesn't reliably produce lasting immunity |
| Parasite behaviour | Evades/suppresses immune responses, changes surface antigens |
| Implication | Hard to design a vaccine that does better than natural infection at conferring immunity |
Answer: (b) Man does not develop immunity to malaria during natural infection.
Why each option is right or wrong
- (a) Incorrect. Multiple Plasmodium species complicate things, but this is not the primary vaccine-development obstacle.
- (b) CORRECT. The fact that natural infection doesn't confer lasting immunity is the central reason effective vaccine design is so difficult.
- (c) Incorrect. This is factually wrong — vaccines exist against non-bacterial pathogens too.
- (d) Incorrect. The intermediate-host status of humans is a biological fact, but not the primary vaccine-development obstacle.
Key point
Malaria vaccine development is hard mainly because natural infection does NOT confer lasting immunity — the parasite evades/suppresses immune defenses, unlike diseases where surviving infection protects you long-term.
Remember
Malaria vaccines are hard to develop mainly because humans don't develop lasting immunity even after natural infection.
Common mistakes
- Picking a true but secondary biological fact (multiple species, intermediate host) over the core immunity-related reason.
- Believing the false claim that vaccines can only target bacteria.
- Not understanding why lack of natural immunity specifically complicates vaccine design.
Exam tip
The core malaria-vaccine challenge: natural infection itself doesn't reliably build immunity, so there's no natural immune 'blueprint' for a vaccine to replicate.
Sources
- Louis H. Miller et al. — "The Pathogenic Basis of Malaria", Nature, vol. 415 (2002)
- World Health Organization — Initiative for Vaccine Research: Malaria vaccines