Background: Due to reduced placental antibody transfer in HIV-1-infected women, their children are born with lower measles antibody levels when compared to children from non-HIV-infected mothers. One can then hypothesize that children from HIV-1-infected mothers will be susceptible to measles at an earlier age.

Methods: 36 children born to HIV-1-infected mothers (HIV-group [6 HIV-1- infected and 30 seroreverted]), and 23 healthy children born to non-HIV-infected mothers (CNT group) were compared.  Maternal blood samples were collected when children started follow-up, and children’s blood samples were collected at 0-2 months, 6 months, and 9 months of age. Antibody levels were evaluated using indirect ELISA. Statistical analyses were performed on log-transformed data.

Results: Mean antibody levels from HIV and CNT groups were similar (2.44 IU/mL and 2.28 IU/mL, respectively; t test, p=0.83). By contrast, mean measles antibody levels at 0-2 months were significantly lower in children born to HIV-1-infected mothers than in those from CNT group (0.98 IU/mL and  2.44 IU/mL, respectively; t test, p=0.012). Unexpectedly, at 6 months of age, both groups had similar mean antibody level (0.039 IU/mL for HIV group and  0.033 IU/mL for CNT group; t test, p=0.56). The number of children with antibody levels lower than the protective level (0.12 IU/mL) in both groups was also similar (86% and  87%, respectively; Fisher exact test, p=1.0). At 9 months of age, this similarity was maintained but now 95% of children in both groups did not have protective antibody levels (Fisher exact test, p =1.0).

Conclusions: Children born to HIV-1-infected mothers have lower measles antibody levels at birth. However, at 6 months of age, > 86% of all children are susceptible to measles, and that figure increases to 95% at 9 months of age. These results suggest that the best age for measles vaccine administration should be reevaluated, in order to shorten the period of susceptibility to that life-threatening disease.