Catch-up vaccine schedule: starting late or behind

How does the CDC catch-up schedule work?

The CDC catch-up schedule lists, for each vaccine, the youngest age for the first dose, the shortest gap between doses, and how those change with the child's age. The gaps are minimums. You can wait longer between doses, and the series continues from where it stopped. The CDC's general guidance says an interruption does not require restarting a series or adding extra doses.

See the glossary for minimum age, minimum interval and the 4-day grace period.

Which doses can age out?

Some vaccines need fewer doses for a healthy child who starts later, because the infant boosters exist to extend protection through early childhood. This is the effect of the CDC rules, not a shortcut:

Hepatitis B (3 doses), MMR (2), varicella (2) and hepatitis A (2) keep the same number of doses however late they start. Rotavirus cannot be caught up once past its age limits. The trade-off for any reduction is a longer time with less protection; the delay overview and each vaccine's delay page explain it.

What if we have fallen behind on a series?

• Count the doses already given; they stay valid.
• Give the next dose once its minimum interval has passed.
• Check the child's current age against the catch-up rules for each vaccine, since the number of remaining doses can change with age.
• Ask your practitioner to confirm the order and which shots to combine at each visit.

The scheduler does this arithmetic for you: enter the shots already given and it plans only what is left.

What should you bring to the visit?

• Your child's immunization record with the date of every dose, and the brand if it is shown.
• Records from any previous clinic, or a request for them if you have moved.
• Your state's school deadline and requirements (see by state).
• A printed plan and your questions; see the conversation guide.
• Notes on any illness, allergy or medical condition your practitioner should know about.

Vaccine-by-vaccine catch-up rules

• Hepatitis B: The series is never restarted. If a dose is late, the next dose is given once the minimum interval has passed.
• DTaP: The first three doses cannot be skipped. A fourth dose given at age 4 or later, at least 6 months after dose 3, can end the series without a fifth.
• Polio (IPV): The final dose must be given at age 4 or later, and at least 6 months after the previous dose.
• Hib: The number of doses depends on age at the first dose: 3 if started at 7 to 11 months, 2 at 12 to 14 months, and 1 at 15 to 59 months.
• PCV: The number of doses depends on age at the first dose: 3 if started at 7 to 11 months, 2 at 12 to 23 months, and 1 at 24 to 59 months for a healthy child.
• Rotavirus: There is no late catch-up. The first dose must be given before 15 weeks of age (by 14 weeks, 6 days) and all doses before 8 months.
• MMR: Two doses are always needed. The first is given at 12 months or later; the second at least 4 weeks after.
• Varicella: Two doses are always needed. The first is given at 12 months or later.
• Hepatitis A: Two doses are given at least 6 months apart, the first at 12 months or later.