Guide
How many doses does each vaccine need by start age?
For a healthy child, 1 dose of Hib or PCV is enough if the series starts at 2 years, DTaP can end at 4 doses instead of 5, and hepatitis B, MMR and varicella never drop. The table below shows every case. A later start shortens the series but lengthens the time a child is unprotected.
Key takeaways
- A healthy child who starts Hib at 15 to 59 months needs 1 dose, and one who starts PCV at 24 to 59 months needs 1 dose; from age 5 neither is routinely needed (CDC catch-up schedule).
- DTaP can finish in 4 doses instead of 5, and polio (IPV) in 3 instead of 4, when the final dose is given at age 4 or later and at least 6 months after the previous dose.
- Hepatitis B stays at 3 doses, MMR and varicella at 2, and hepatitis A at 2, however late the first dose is given.
- Rotavirus is not possible after its cutoffs: the first dose must be given before 15 weeks of age and no dose on or after 8 months.
- A later start means fewer doses but a longer time without protection; the CDC and AAP recommend on-time vaccination as the default.
Doses needed, by age at the first dose
| Vaccine | Birth | 6 months | 12 months | 2 years | 4 years | 5 years |
|---|---|---|---|---|---|---|
| HepB 3 on time | 3 | 3 | 3 | 3 | 3 | 3 |
| DTaP 5 on time | 4–5 a | 4–5 a | 4–5 a | 4–5 a | 4 | 4 |
| IPV 4 on time | 3–4 a | 3–4 a | 3–4 a | 3–4 a | 3 | 3 |
| Hib 4 on time | 4 | 4 | 2 | 1 | 1 | Not needed |
| PCV 4 on time | 4 | 4 | 2 | 1 | 1 | Not needed |
| RV 3 on time | 3 | Not possible b | Not possible b | Not possible b | Not possible b | Not possible b |
| MMR 2 on time | 2 | 2 | 2 | 2 | 2 | 2 |
| VAR 2 on time | 2 | 2 | 2 | 2 | 2 | 2 |
| HepA 2 on time | 2 | 2 | 2 | 2 | 2 | 2 |
Fewer doses than the on-time schedule. Counts are for the vaccine series in this planner; flu and COVID-19 are seasonal or optional and are not modeled as fixed series.
Reading the table
- Hib falls to 2 doses when started at 12 to 14 months and 1 when started at 15 to 59 months (3 age bands in the CDC catch-up table); from age 5 a healthy child does not need it.
- PCV falls to 2 doses when started at 12 to 23 months and 1 when started at 24 to 59 months; from age 5 a healthy child does not routinely need it.
- DTaP and polio depend on when the final dose is given, not only when the series starts. The count is 4–5 (DTaP) or 3–4 (IPV) if the final dose is given before age 4, and the lower number if it is at 4 or later and at least 6 months after the previous dose.
- Hepatitis B, MMR, varicella and hepatitis A keep their dose counts. MMR, varicella and hepatitis A cannot start before 12 months, so an earlier column simply shows the count that will apply once the first dose is possible.
Notes
- Range: the higher number applies if the final dose is given before age 4, the lower if the final dose is at 4 years or later and at least 6 months after the previous dose (CDC catch-up schedule notes).
- Not possible: the first rotavirus dose must be given before 15 weeks of age and no dose may be given on or after 8 months.
- On-time counts are the CDC routine infant series as encoded in this planner; some brands need fewer doses (for example some Hib and rotavirus products), so your practitioner will confirm the count for the product used.
- Counts come from the CDC Catch-up Immunization Schedule (Table 2), its notes and the CDC polio and pneumococcal/Hib job aids, applied to a healthy child. The table is generated from the same data as the scheduler.
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