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

Explanation

The correct answer is option 1, i.e., “Malaria is caused by several species of Plasmodium”. Here`s an explanation for each option: Option 1: Malaria is in fact caused by various species of the Plasmodium, such as Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Each species has a unique lifecycle and resistance profile, which makes it difficult to develop a single effective vaccine for all types. Option 2: It`s incorrect to say that humans do not develop immunity to malaria during a natural infection. Partial immunity can be developed, but it takes time and multiple bouts of infections to acquire. This, however, does not undermine the efforts to develop a vaccine. Option 3: This option is also incorrect as vaccines can be developed not only against bacteria, but also against various viruses and other parasitic organisms. There are even vaccines available for certain types of cancer. Option 4: Even though humans are intermediate hosts in malaria, it doesn`t have any particular relevance to the development of a malaria vaccine. The definitive host for malaria is the mosquito, which doesn`t affect the creation of a human vaccine.