1 Infectious Diseases, Department of Clinical Research, Det Sundhedsvidenskabelige Fakultet, SDU2 Faculty of Health Sciences, University of Southern Denmark, Odense C, Denmark.3 unknown4 Statens Serum Institute, Copenhagen5 Bandim Health Project, INDEPTH Network, Bissau, Guinea-Bissau. Electronic address: firstname.lastname@example.org Research Center for Vitamins and Vaccines (CVIVA), Statens Serum Institute, Denmark. Electronic address: email@example.com Bandim Health Project, INDEPTH Network, Bissau, Guinea-Bissau. Electronic address: firstname.lastname@example.org Ph.d.-studienævnet for Medicin9 Infectious Diseases, Department of Clinical Research, Det Sundhedsvidenskabelige Fakultet, SDU
In low-income countries early measles vaccine (MV) is associated with reduced child mortality which cannot be explained by prevention of measles. A large thymus gland in infancy is also associated with reduced mortality. We hypothesized that early MV is associated with increased thymic size. Within a randomized trial providing MV at age 4.5 and 9 months or MV only at age 9 months, thymic size was assessed by ultrasound at age 4.5 months, before randomization to early MV or no early MV, and 4 weeks later. Among 656 children, there was no effect of early MV on thymic size, the geometric mean size ratio being 0.99 (95% CI: 0.96-1.02). In a post hoc analysis early MV was associated with a negative effect in healthy children but a positive effect in ill children. In conclusion, early MV at age 4.5 months had no overall effect on thymus size 4 weeks later. Trial registration: http://clinicaltrials.gov, NCT01486355.