Changes to the national childhood immunization schedule (NCIS) can have a potential impact on vaccine uptake in the community. The NCIS in Singapore has undergone several revisions over the years, with the most recent modification on 1 November 2020. The new NCIS includes, as routine, the influenza and the varicella vaccine, as well as two combination vaccines, the measles, mumps, rubella and varicella vaccine (MMRV), and the hexavalent diphtheria, acellular pertussis, tetanus, haemophilus influenza b, injectable polio, and hepatitis B vaccine (6-in-1). This retrospective database study aims to assess the effect of the new NCIS on (a) the vaccination uptake of children at 6 and 12 months and (b) the cost difference to the healthcare system and to parents. One-year vaccination data from two cohorts of children immunized according to the old (n = 10,916) and new NCIS (n = 10,299) were extracted, respectively, from their electronic medical records. The vaccine uptake at 6 and 12 months increased by 10.8 and 2.1%, respectively, with the new NCIS as compared to the old NCIS. The mean number of required visits to the primary care clinic for each child was reduced from six to four. There is an estimated 6.41% cost reduction with the new NCIS.