Children receive vaccines at several key ages: birth, 2 months, 4 months, 6 months, 12 to 15 months, 4 to 6 years, 11 to 12 years, and 16 years. The busiest stretch is the first 15 months of life, when babies get the majority of their shots. After that, visits space out to a handful of boosters before kindergarten and another round in the preteen years.
Why Vaccines Start So Early
Newborns and young infants are the most vulnerable to serious infections because their immune systems haven’t encountered many pathogens yet. Babies do get some temporary protection from antibodies passed through the placenta and breast milk, but that “borrowed” immunity fades within months and varies from baby to baby depending on the mother’s own antibody levels and whether the baby was born full-term or early.
Vaccines given in infancy take advantage of that shrinking window. Some, like the shots protecting against diphtheria, tetanus, and whooping cough, require multiple doses to build real protection, so the series needs to start early enough that a baby’s own immune system is trained before the borrowed antibodies disappear. In short, the schedule is designed to stay ahead of the diseases most likely to harm a child at each stage of life.
Birth Through 6 Months
The very first vaccine most babies receive is the hepatitis B shot, typically given in the hospital within 24 hours of birth. A second dose of hepatitis B follows at 1 month.
At 2 months, the schedule picks up considerably. This visit usually includes shots protecting against diphtheria, tetanus, and whooping cough (DTaP), polio, Haemophilus influenzae type b (Hib, a cause of meningitis), pneumococcal disease, and rotavirus (given as oral drops rather than a shot). The same set of vaccines is repeated at 4 months, and most of them come around again at 6 months to complete or continue the series. A third dose of hepatitis B is also given sometime between 6 and 18 months.
Flu shots become available starting at 6 months of age and are recommended every year from that point forward. COVID-19 vaccines are also approved starting at 6 months.
12 to 15 Months
The next cluster of visits falls around a child’s first birthday. This is when kids typically receive their first dose of MMR (measles, mumps, and rubella), their first dose of the chickenpox vaccine, and their first dose of the hepatitis A vaccine. Booster doses of the Hib and pneumococcal vaccines are also given during this window to reinforce the protection built during infancy.
A second dose of hepatitis A follows at least six months after the first, usually between 18 and 23 months.
4 to 6 Years: The Kindergarten Boosters
Before starting school, children need booster doses of several vaccines they first received as babies. Almost every state requires four specific vaccines for kindergarten enrollment: DTaP, MMR, polio, and chickenpox. These boosters strengthen immunity that can weaken over time and ensure kids are well-protected as they enter a setting where infections spread easily.
After this round, most children won’t need another vaccine visit for several years.
11 to 12 Years: The Preteen Visit
The preteen checkup brings a new set of vaccines tailored to the risks of adolescence and young adulthood:
- Tdap: A single booster dose that refreshes protection against tetanus, diphtheria, and whooping cough. This is a different formulation than the DTaP given in early childhood.
- HPV vaccine: Protects against the strains of human papillomavirus most likely to cause certain cancers later in life. When started at 11 or 12, only two doses are needed (spaced 6 to 12 months apart). Starting after age 15 requires three doses.
- Meningococcal ACWY: The first dose of a vaccine protecting against four strains of bacterial meningitis. A second dose is given at age 16.
16 to 18 Years
At 16, teens receive their second dose of the meningococcal ACWY vaccine. This booster is particularly important for teenagers heading toward college, where living in close quarters like dormitories raises the risk of meningococcal disease.
A separate meningococcal B vaccine, covering a fifth strain of meningitis, is available for teens between 16 and 18. Unlike most childhood vaccines, this one is based on shared decision-making between families and their pediatrician rather than a blanket recommendation for every teen. Two doses are needed if the family chooses to go ahead with it.
Annual Vaccines
Two vaccines fall outside the age-based milestone schedule because they’re recommended every year. The flu shot is recommended annually for everyone 6 months and older. For the first season a child gets a flu shot, two doses are typically needed, spaced four weeks apart. After that, one dose per year is sufficient. COVID-19 vaccines follow a similar annual pattern, with the number of doses depending on a child’s age and vaccination history.
What If Your Child Missed a Dose
A missed vaccine doesn’t mean starting the entire series over. The CDC’s catch-up schedule makes clear that a vaccine series never needs to be restarted, no matter how much time has passed between doses. Your child’s pediatrician can look at which doses were given, calculate the minimum intervals between remaining doses, and put together a plan to get back on track. In many cases, multiple catch-up doses can be given at a single visit to close the gap quickly.