Background. In 2013–2014, a measles outbreak spread through the Netherlands. To protect young infants, measles-mumps-rubella (MMR) vaccination was offered to those aged 6–14 months in municipalities with routine first-dose MMR vaccine coverage of <90%. We assessed the tolerability of this early administration of MMR vaccine.
Methods. After study entry (n = 1866), parents of eligible infants (n = 10 097) completed a questionnaire (n = 1304). For infants who received an early MMR vaccine dose (n = 962), we asked for information about adverse events (AEs) associated with the dose. AE frequencies were compared between infants aged 6–8, 9–11, and 12–14 months. Using multivariable logistic regression, we assessed the association between the risk of AEs and age at early MMR vaccination.
Results. The response rate was 13%. Parents of 59 infants (6.1%) and 350 infants (36.4%) who received early MMR vaccination reported local and systemic AEs, respectively. Parents of infants vaccinated at 6–8 months of age reported systemic AEs less frequently (32%) than parents of children vaccinated at 9–11 months (45%) and 12–14 months (43%) of age (P = <.001). For local AEs, there were no differences (5%, 7%, and 10%, respectively; P = .08). Compared with vaccination at 6 months, all older infants except those aged 14 months showed an increased risk for any AE and for systemic AEs starting 5–12 days after vaccination.
Conclusions. Early MMR vaccination is well tolerated, with the lowest AE frequencies found in infants aged 6–8 months. It is a safe intervention for protecting young infants against measles.