The overall objective is to evaluate the effect of exposure to Plasmodium (P.) falciparum erythrocytic stage antigens during different periods of infancy on the development of naturally acquired immunity (NAI).

Hypothesis: Exposure to P. falciparum prior to 5 months of age does not result in the development of NAI, while exposure to P. falciparum after 5 months of age leads to the development of NAI. The risks of clinical malaria and anaemia during the second year of life will be compared between cohorts, as well as their correlations with the type and quality of immune responses (antibodies to several P. falciparum antigens, cytokines), oxidative stress markers and host genetic factors. These results should shed light on the determinants of the development of anti-P. falciparum responses early in life and the potential constraints to early life immunisation.

Inclusion Criteria:

Inclusion criteria for pregnant women:

• Healthy HIV-negative pregnant females less than 50 years of age who attend the voluntary counseling and testing (VCT) center at the Maragra or Manhiça antenatal clinic,
• Permanent residents of the Manhiça area and expecting to be living in the area with their infant for at least 2 years.

Inclusion criteria for newborn infants:

• Healthy infants, weighing >= 2 kg and having an alive mother.

Exclusion Criteria:

Exclusion criteria for pregnant women:

• Plan to leave the area in less than 2 years from the start of the study;
• Women not willing to get tested for HIV infection at the VCT center;
• Test positive for HIV;
• Not willing to provide informed consent;
• Cannot understand either Portuguese or Changana (consent forms are written in these languages).

Exclusion criteria for newborn infants:

• Any obvious congenital malformation;
• Any signs of cerebral asphyxia;
• Any obvious neonatal infection;
• Same gender Twins;
• Low birth weight (<2 kg).