Guide
Catching up on vaccines at 4 years
A 4-year-old with no prior vaccines needs about 18 doses over as few as 9 visits (18 visits at one dose per visit), against 26 doses on the on-time schedule.
Key takeaways
- Of the 26 on-time doses in these 8 vaccines, 18 are still needed at 4 years: DTaP 4 instead of 5, IPV 3 instead of 4, Hib 1 instead of 4 and PCV 1 instead of 4.
- From 4 years, 3 doses per visit takes 9 visits over 10 months, ending at 4 years 10 months; one dose per visit takes 18 visits over 20 months.
- Rotavirus is no longer possible: the final dose is due before 8 months and this child is 3 years 4 months past it.
- By 4 years, an on-time child would already have had 22 of these routine doses; this plan counts none of them as given.
Doses needed at 4 years, vaccine by vaccine
| Vaccine | On time | If started now | Planner minimum | Why |
|---|---|---|---|---|
| HepB (Hepatitis B) | 3 | 3 | 3 | No reduction. Gaps of 4 weeks and 8 weeks between doses. |
| DTaP (Diphtheria, Tetanus & Pertussis) | 5 | 4 | 4 | 4-dose delayed path (4th dose at age ≥4 replaces doses 4 & 5). |
| IPV (Polio (Inactivated)) | 4 | 3 | 3 | 3-dose delayed path (3rd dose at age ≥4 is the final dose). |
| Hib (Haemophilus influenzae type b) | 4 | 1 | 1 | Start 15–59 mo: a single dose completes Hib. |
| PCV (Pneumococcal Conjugate) | 4 | 1 | 1 | Start 24–59 mo (healthy): a single dose completes PCV. |
| MMR (Measles, Mumps & Rubella) | 2 | 2 | 2 | No reduction. Second dose at least 4 weeks after the first. |
| VAR (Varicella (Chickenpox)) | 2 | 2 | 2 | No reduction. Second dose at least 3 months after the first. |
| HepA (Hepatitis A) | 2 | 2 | 2 | No reduction. The two doses are at least 6 months apart. |
"If started now" and "Planner minimum" agree at 4 years. A range such as 4–5 means the lower number applies when the final dose is given at age 4 or later.
Visits and finish age
Starting at 4 years, three doses per visit needs 9 visits fewer than one at a time and ends 10 months sooner. The required gaps set the floor: the earliest plan ends 10 months after the first visit, at 4 years 10 months.
| Pace | Visits | Doses placed | Last visit at |
|---|---|---|---|
| 1 dose per visit, 1 month apart | 18 | 18 | 5 years 8 months |
| 3 doses per visit, 1 month apart | 9 | 18 | 4 years 10 months |
| Planner preset: one vaccine per visit, 2 months apart | 18 | 18 | 6 years 10 months |
Pace figures come from the same engine as the planner, with a healthy child, the planner's default vaccines and no prior doses.
Rules that apply at 4 years
- Rotavirus (RV) is not possible: its final dose must come before 8 months, which this child passed 3 years 4 months ago.
- At 4 years the planner uses 1 dose of Hib; the CDC bands are 3 doses if the first is at 7 to 11 months; 2 doses if the first is at 12 to 14 months; 1 dose if the first is at 15 to 59 months, and none from age 5.
- At 4 years the planner uses 1 dose of PCV; the CDC bands are 3 doses if the first is at 7 to 11 months; 2 doses if the first is at 12 to 23 months; 1 dose if the first is at 24 to 59 months, and none from age 5.
- At 4 years DTaP is 4 doses and polio 3: the last dose goes at age 4 or later and at least 6 months after the one before, and a 4-year-old is already at or past that age, so only the gap matters.
- At 4 years, hepatitis A needs 6 months between its two doses, the longest fixed wait in the plan.
Questions parents ask at this age
How many vaccines does a 4-year-old need to catch up?
At 4 years the plan is 18 doses (HepB 3, DTaP 4, IPV 3, Hib 1, PCV 1, MMR 2, VAR 2, HepA 2) out of 26 on the on-time series, of which an on-time child has had 22 by now.
How many visits will a 4-year-old need?
From 4 years: as few as 9 with up to 3 doses per visit (finishing at 4 years 10 months), 18 with one dose per visit and 1 month between (5 years 8 months), or 18 on the planner's one-vaccine-per-visit preset with 2 months between (6 years 10 months).
Why does a 4-year-old need one fewer DTaP dose?
The 5th DTaP dose is not needed when the 4th is given at age 4 or later and at least 6 months after dose 3. A 4-year-old already qualifies for the final dose, so DTaP is 4 doses instead of 5, and polio 3 instead of 4.
Do Hib and PCV still matter at 4?
One dose each, and the window closes in 12 months. At one dose per visit the plan lasts 18 visits and ends at 5 years 8 months, so those two doses should go in the first visits rather than at the end.
Build the plan for 4 years
Enter the birth date and any doses already given; the planner counts them and spaces the rest.
Open the planner in catch-up mode One vaccine per visit Up to 4 per visitSources
Primary sources only. Links open the publisher's own page.