But concern exists about a possible rebound when treatment is stopped, warn the authors.
The study followed over 2,400 infants in Ghana who were given a preventive treatment for malaria or a placebo (dummy pill) when they received routine vaccinations and at 12 months of age.
Preventive treatment reduced malaria by 25% and anaemia by 35% up to age 15 months. However, malaria levels increased 20% when treatment was stopped in the second year of life.
The protective effect was also substantially lower than that reported from previous studies in Tanzania.
Because these findings run counter to earlier studies, the authors suggest that more data are needed to decide on the appropriate dose schedule for preventive drugs in areas with high seasonal transmission and its interaction with insecticide treated bed nets.
However, intermittent preventive treatment in infants, linked to the expanded programme of immunisation schedule, has the potential to reduce the burden of malaria even in areas with high seasonal transmission, they conclude.