Quantitative information on parents’ preferences regarding multiple vaccine injections and on work-loss due to vaccination is important to guide decision making on the use of combination vaccines for universal vaccination. Our survey in families of 1347 toddlers (18–24 months) and 1315 adolescents residing in Flanders, Belgium, revealed common attitudes in both age groups. The majority of parents would allow maximum two injections in one visit. 39% were not willing to pay anything to avoid a concomitant injection, whereas the remainder mentioned amounts around a median of €20. The responses were hardly influenced by the socioeconomic determinants studied and the concordance between the number of concomitant injections parents would allow and their willingness-to-pay assessed by an open-ended question was limited, which suggests that more sensitive quantification using other methods would be useful. Work-loss due to vaccination was assessed for infants only and was rare (4.5%).