Enter the child's age and vaccines already received. Get a personalized catch-up plan with minimum intervals and next-due dates.
Check off each dose the child has received. Leave unchecked if not given or unknown.
A catch-up immunization schedule is a plan for children or adolescents who have missed one or more recommended vaccine doses. The CDC and Advisory Committee on Immunization Practices (ACIP) publish catch-up schedules that specify minimum ages for each dose, minimum intervals between doses, and the maximum number of doses needed at each age.
The key principle of catch-up immunization is that vaccine series do not need to be restarted regardless of how much time has elapsed between doses. Previously administered valid doses still count, so the catch-up plan focuses on the remaining doses needed.
To determine the catch-up plan: (1) Identify the child's current age; (2) Review the documented vaccine history to count valid doses of each antigen; (3) Compare against the CDC recommended schedule to determine which doses are missing; (4) Apply minimum interval rules to calculate the earliest dates for each catch-up dose.
Important rules: Doses given before the minimum age are generally invalid and may need to be repeated. A 4-day grace period applies for doses given slightly before the minimum age or interval. Some vaccines like Hib and PCV have different schedules depending on the age at which the catch-up series starts.
Minimum intervals are the shortest acceptable time between doses of the same vaccine. They ensure adequate immune response. Common examples: DTaP doses 1-3 require a 4-week minimum interval, IPV doses have 4-week minimum intervals between early doses and 6 months before the final dose, and MMR doses require 4 weeks minimum between doses.
Administering vaccines too close together (shorter than the minimum interval) may reduce the immune response and the dose may be considered invalid. The general ACIP rule: if the interval was at least 4 days shorter than the minimum (the "4-day grace period"), the dose can still be counted as valid.
Yes. Multiple vaccines can and should be given at the same visit when a child is behind on the schedule. This is both safe and recommended by the CDC. There is no limit to the number of vaccines that can be administered simultaneously, and giving multiple vaccines at once does not reduce their efficacy or increase the risk of adverse effects.
Some considerations: Live injectable vaccines (MMR, Varicella) that are not given at the same visit should be separated by at least 28 days. Combination vaccines (e.g., Pediarix = DTaP-IPV-HepB) can reduce the number of injections needed. When many catch-up vaccines are due, providers may prioritize by disease risk and schedule additional visits 4 weeks apart.
When a child starts a vaccine series late, the number of doses needed may be reduced. For example, if a child receives their first Hib vaccine at 15 months or older, they only need one dose instead of the usual 3-4 dose series. Similarly, PCV15/PCV20 requires only one dose if started at 24 months or older in healthy children.
This is because older children have more mature immune systems that respond more robustly to vaccines. The CDC catch-up schedule provides specific dose recommendations based on the child's age at the first dose of each series, with fewer doses generally needed when starting at older ages.
School-entry vaccine requirements vary by state, but most states require proof of immunization for DTaP/Tdap (diphtheria, tetanus, pertussis), IPV/OPV (polio), MMR (measles, mumps, rubella), Varicella (chickenpox or evidence of immunity), and Hepatitis B. Many states also require Hepatitis A and Meningococcal vaccines.
Children who are behind on vaccines can still attend school in most states with a provisional enrollment plan showing they are in the process of catching up. Medical, religious, or philosophical exemptions vary by state. The catch-up calculator helps identify exactly which doses are still needed to meet school entry requirements.