Baby Vaccines: Which Ones, and When

Why does the timing of baby vaccines matter?

The schedule is not arbitrary. Each vaccine is timed based on two things: when a baby's immune system is mature enough to mount a protective response, and when the risk from the disease itself is highest 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling.

Some diseases — particularly whooping cough (pertussis) and certain bacterial meningitis infections — are most dangerous in the first few months of life, before a baby could be fully vaccinated if the schedule started later. This is why several vaccines begin at birth or at the two-month visit.

Some vaccines require multiple doses because immune memory builds gradually over a series — a single dose does not produce the same lasting protection as the full sequence. The Pink Book chapter on vaccination principles explains that active immunity from a series typically lasts longer than immunity from a single dose 3Ref 3Centers for Disease Control and Prevention (2024).Chapter 2: General Best Practice Guidance for Immunization (Epidemiology and Prevention of Vaccine-Preventable Diseases, The Pink Book).Principles of vaccine timing, contraindications, precautions, and guidance for special populations including immunocompromised children and premature infants.

What shots does my baby get at birth through one month?

The hepatitis B vaccine (HepB) is typically given within the first 24 hours of birth, before the baby leaves the hospital 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling. Hepatitis B is a serious liver infection that can spread from mother to baby during delivery; early vaccination closes this window. A second dose follows at one to two months, and a third and final dose in the series comes at six months.

What happens at the two-month well-child visit?

The two-month visit is the busiest vaccine appointment in a child's life. Babies typically receive vaccines against 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling:

• DTaP — diphtheria, tetanus, and whooping cough
• Hib — Haemophilus influenzae type b, a cause of bacterial meningitis
• IPV — inactivated polio
• PCV — pneumococcal bacteria, which cause pneumonia and meningitis
• RV — rotavirus, a common cause of severe infant diarrhea

Some are given as combination shots to reduce the number of injections. Fussiness and a low-grade fever after the two-month visit are common and expected — the immune system is doing its job. Your pediatrician can advise on comfort measures.

What vaccines are given at four and six months?

The four-month and six-month visits repeat most of the same vaccines as the two-month visit — these are the second and third doses in the series needed to build full protection 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling. Hepatitis B's third dose is given at six months.

The flu vaccine (influenza) becomes relevant at six months: it is the earliest age it can be given, and annual flu vaccination is recommended for everyone six months and older, every year 2Ref 2Centers for Disease Control and Prevention (2024).Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2024–25 Influenza Season.Annual flu vaccination is recommended for everyone six months of age and older.

What new vaccines appear around the first birthday?

Around the first birthday, the schedule introduces vaccines that work better once a baby's immune system is a bit more mature 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling. These include:

• MMR — measles, mumps, and rubella
• Varicella — chickenpox
• Hepatitis A — a two-dose series
• PCV booster

The Hib and DTaP series also receive doses around this time. Some may be combined into a single injection (MMRV combines MMR with varicella).

Is the series complete by age two?

The period from 15 to 24 months completes several series. DTaP, Hib, IPV, hepatitis A, and PCV each receive their final scheduled doses 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling. By age two, the core of the childhood immunization series is substantially complete. Your child's provider keeps a record and will let you know if a dose was missed or if the schedule needs to be caught up.

What if a dose was delayed?

If a dose is delayed — due to illness at the scheduled visit, insurance changes, or any other reason — your child's provider will use the CDC-endorsed catch-up schedule to get back on track safely 1Ref 1Issa AN, Wodi AP, Moser CA, Cineas S (2025).Advisory Committee on Immunization Practices Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger — United States, 2025.The childhood vaccine schedule — timing of each dose, which vaccines are given at each well-child visit, and catch-up scheduling. You do not need to start the entire series over. Combination vaccines (one injection that covers two or three diseases at once) are common and reduce the total number of shots needed.

For children with premature birth, most follow the same vaccine schedule based on chronological age rather than gestational age, though a neonatologist and pediatrician will guide any adjustments. For children with immunocompromising conditions, some live vaccines — such as MMR, varicella, and rotavirus — may be deferred; the provider will individualize the schedule based on ACIP guidance 3Ref 3Centers for Disease Control and Prevention (2024).Chapter 2: General Best Practice Guidance for Immunization (Epidemiology and Prevention of Vaccine-Preventable Diseases, The Pink Book).Principles of vaccine timing, contraindications, precautions, and guidance for special populations including immunocompromised children and premature infants.