Vaccine antibody responses in children with inborn errors of metabolism on protein-restricted diets: an overlooked silent risk?

OBJECTIVES: Despite routine vaccination recommendations, concerns remain about vaccine-induced immune responses in some patients with inborn errors of metabolism (IEM). Therefore, antibody levels against vaccine antigens should be monitored to detect possible immune dysfunction. The aim of this study is to evaluate the vaccine antibody responses among children with IEM who have to follow protein restricted diet, and to compare with those in healthy children, and also to identify the factors affecting vaccine antibody responses in these patients. METHODS: Anti-HBs and measles immunoglobulin G results of 25 patients diagnosed with amino acid metabolism disorder; phenylketonuria, organic acidemia, homocystinuria and urea cycle disorder, and 58 healthy children of the same age and gender were recorded. Seropositivity rates and titers were compared between two groups, and also with age, daily protein intake, diet duration, total protein, albumin and hemoglobin levels. RESULTS: Seropositivity against hepatitis B was 64 %, and against measles was 80 % in the patient group, and these seropositivity rates were lower than those in the control group. These results show that the trend of the findings was maintained even after adjustment for age. No significant differences in vaccine antibody responses was found among disease subgroups. CONCLUSIONS: As children receiving long-term protein-restricted diets may demonstrate reduced vaccine antibody responses, these findings warrant confirmation in larger prospective studies. We believe that vaccine antibody responses should also be reviewed during metabolic follow-up in these patients.