RESUMEN
This study evaluated the vaccination response to Haemophilus influenzae type b (Hib) in malnourished pregnant women (MN), cord blood (CB) and in infants at two and six months of age for comparison with a control group (C). Twenty-eight malnourished pregnant women and 29 pregnant controls were immunized with conjugated Act-HIB® in the third trimester of pregnancy. Blood samples were collected from all before the immunization, during labor (post immunization), and from CB. All infants were immunized with Hib vaccine according to normal vaccine schedule and sera were collected at two and six months of age. Antibody levels to polyribosylribitol phosphate (PRP) were similar for both groups. Preimmunization: MN 1.94 µg/mL, C 1.68 µg/mL; post-vaccination: MN 18.53 µg/mL and C 17.55 µg/mL; in CB from MN 14.46 µg/mL and from C 17.04 µg/mL. Infants from MN and C mothers presented respectively at two months: 5.18 µg/mL and 8.60 µg/mL and at six months: MN 3.42 µg/mL and C 2.18 µg/mL. Antibody levels were similar in both groups studied (p = 0.485), however the vertical transmission rate was 14 percent lower in the MN pregnant group. Levels of antibodies > 0.15 µg/mL were found in all newborns from the MN pregnant group. Pregnant MN presented an immunological response to Hib vaccine similar to group C, however, vertical transmission rate of antibodies to PRP in the MN pregnant group was 14 percent lower than that in C, suggesting a less efficient passage of antibodies within this group.