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 ?

An effective malaria vaccine is difficult mainly because malaria is caused by several Plasmodium species and because the parasites exhibit complex life cycles and high genetic/antigenic diversity. Multiple human-infecting species (P. falciparum, P. vivax, P. ovale, P. malariae and others) mean a single vaccine may not protect against all pathogens or disease forms [1]. In addition, extensive antigenic diversity and strain-specific immune responses in Plasmodium make it hard to identify conserved targets that elicit broad, durable protection; this antigenic variation undermines vaccine efficacy in trials and necessitates species- and strain-focused strategies [2]. These factors together explain why option (1) is the best choice.

Sources

1. [1] https://www.nature.com/articles/s41392-025-02246-3
2. [2] https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2014.00359/full