The present invention relates to novel vaccines against malaria infections, based on recombinant viral vectors, such as alpha viruses, adenoviruses or vaccinia viruses. The recombinant viral-based vaccines can be used to immunize against different Plasmodium infections, such as infections by P. falciparum or P. yoelii. Novel codon-optimized circumsporozoite genes are disclosed. Preferably, replication-defective adenoviruses are used, derived from serotypes that encounter low titers of neutralizing antibodies. The invention, therefore, also relates to the use of different adenoviral serotypes that are administered to elicit a strong immune response, either in single vaccination set-ups or in prime-boost set-ups in which compositions based on different serotypes can be applied.