Malaria remains an important cause of illness in young infants. Our clinical and epidemiological studies in Papua (Indonesia) have shown the magnitude of malaria morbidity in infants in the first 5 years of life, including recurrent episodes of malaria, anaemia, malnutrition and coinfection. Together these contribute significantly morbidity in early life, and almost certainly to the very high infant mortality rates in this region. However the body of knowledge around infant malaria outside of Africa, where both species P. vivax and P. falciparum are prevalent is considerable smaller. The impact of recurrent vivax malaria and severe anaemia on neurodevelopment and growth in young children is unknown in Papua.

This study therefore aims to provide longitudinal data on the incidence of symptomatic and asymptomatic malaria (P. falciparum and P. vivax) and the associated risk of anaemia. It also provides an opportunity to assess incidence risk of non-malaria febrile illnesses and bacterial co-infections and the long term outcomes in terms of neurodevelopment and growth in a vulnerable age group. The study is a continuation from two already established cohort studies: "STOP MIP", which enrolled pregnant women and followed them until delivery and a "baby-cohort", which enrolled babies from mothers included in the cohort and followed them through their first year of life. Continuous follow up of those babies until they are 4 years old will increase our understanding of long term impact especially of vivax malaria. The cohort will be linked to a randomized controlled trial (RCT) and will offer cohort patients to be enrolled into the RCT when they are diagnosed with malaria (symptomatic), allowing to estimate treatment effectiveness.

Inclusion Criteria:

• Patient enrolled in the Baby-Cohort study

Exclusion Criteria:

• Patients not enrolled in the Baby-Cohort study

The study is designed as a continuation of a cohort of infants from 12 to 48 months of age. This follows on from two previous cohorts: "STOP MIP", which is a cohort of pregnant women followed up until delivery and the "Baby-Cohort study", which enrols babies from mothers in the "STOP MIP" trial and follows them until their first year of live. When participants of the "Baby-cohort Study" reach study end, they are offered to participate in this study.