Immunization schedule

Vaccinations are one of the most effective methods of disease prevention, drastically reducing illness, hospitalizations, and deaths from infectious diseases. In order to prevent a resurgence of vaccine-preventable illnesses in the US, the Centers for Disease Control and Prevention (CDC) and Advisory Committee on Immunization Practices (ACIP) publish yearly immunization schedule recommendations. These schedules are formulated based on extensive research and aim to protect individuals at the age at which they have the highest risk for infection. Specific recommendations are available for the general population (children and adults), individuals with certain health conditions, and those traveling to areas with high rates of infection. Education on the importance of vaccination and the implementation of catch-up schedules for underimmunized individuals are vital to ensuring herd immunity and preventing infectious diseases.

Routine immunization ^[1][2][3]

• Immunizations are a vital component of primary prevention; see “Pathogens affecting unvaccinated individuals.”
• Follow the recommended ACIP immunization schedules.
• Age-appropriate vaccines should be administered at the same visit when feasible; see simultaneous vaccination and combination vaccines.
• Be aware of contraindications for each vaccine. ^[4]
• Identify individuals with risk factors and/or medical indications that necessitate altered immunization schedules.
  • See “Immunization schedule by medical indication.”
  • See the “Special patient groups” section
• Educate individuals on the disease that each vaccine aims to prevent and the possible adverse effects; provide Vaccine Information Statements.
• Report any vaccine-related adverse events to the Vaccine Adverse Event Reporting System (see “Tips and links”).

Vaccine dose is not adjusted for weight but may vary based on age.

It is US federal law to provide a Vaccine Information Statement before the administration of every vaccine. ^[5]

Vaccinations against multiple diseases at the same visit ^[3]

Simultaneous vaccination

Administration of > 1 vaccine on the same day, but in different syringes and at different anatomical locations

• May include a combination of inactivated vaccines, live attenuated vaccines, or immunoglobulins
• Most vaccines can be administered simultaneously; exceptions include:
  • Pneumococcal conjugate vaccine (PCV15 or PCV20 or PCV21) and PPSV23: Do not administer simultaneously. ; ; ; ; ^[6]
  • Pneumococcal conjugate vaccine (PCV15 or PCV20 or PCV21) and MenACWY-D: Do not administer simultaneously. ^[6]

If injectable or nasally administered live vaccines are not administered on the same day, they must be administered ≥ 4 weeks apart. ^[3]

Live oral vaccines (e.g., rotavirus vaccine) may be administered on the same day or at any interval before or after other live vaccines. ^[3]

Combination vaccines ^[3]

Combination of different vaccine components in a single product

• Preferred over simultaneous single-component vaccines, when feasible
• Examples of commonly used combination vaccines:
  • DTaP-IPV-Hib
  • DTaP-HepB-IPV
  • DTaP-IPV-HepB-Hib
  • DTaP-IPV
  • MMRV ^[7]
  • HepA-HepB

Timing and spacing of vaccines ^[3]

• Follow the ACIP recommendations for the minimum age for the first dose and minimum intervals between doses to ensure optimal protection.
• Unapproved delayed or alternate immunization schedules put individuals at risk.

Delayed or missed vaccines (undervaccination) ^[1][2]

• Follow recommended catch-up immunization schedules for undervaccinated individuals.
• Do not restart the immunization series from the beginning.
• Continue with the next dose in the immunization series.

Vaccines administered before the recommended minimum age or interval ^[3]

In general, any vaccine administered ≥ 5 days earlier than the minimum age or interval is considered invalid and needs to be repeated.

• First dose administered ≥ 5 days earlier than the recommended minimum age
  • Repeat the dose when or after the individual attains the minimum recommended age.
  • For live vaccines, repeat the first dose ≥ 28 days after the invalid first dose.
• Additional doses administered ≥ 5 days earlier than the recommended minimum interval
  • Repeat the dose; the minimum interval restarts from when the invalid dose was administered.

Doses administered ≤ 4 days before the minimum age or interval (grace period) are considered valid. ^[3]

This table provides an overview of the ACIP immunization schedule. See the latest CDC recommendations for detailed guidance.

• See also:
  • Immunizations in pregnancy
  • Immunizations in preterm infants
  • Immunizations in men who have sex with men
  • Immunizations in individuals with HIV
  • Immunizations for health care personnel
  • Travel vaccines
  • Contraindications for vaccination

Any mention of vaccine trade names is only for the purposes of identification and should not be considered an endorsement.

For catch-up vaccines, continue with the next dose in the immunization series. Do not restart the immunization series from the beginning. ^[2]

Unapproved delayed or alternate immunization schedules put individuals at risk for vaccine-preventable conditions and complications. ^[3]

Egg allergy is not a contraindication for any influenza vaccination. ^[23]

The youngest recommended age for routine immunization is shown in this table. Refer to the ACIP immunization schedule for details on age ranges, catch-up immunizations, and special considerations.

For individuals ≥ 6 months of age, recommend age-appropriate COVID-19 vaccination and yearly influenza vaccination during influenza season.

The use of combination vaccines can decrease the number of injections needed at each encounter. Combination vaccines are frequently used for the 2-month, 4-month, 6-month, and 4–6-year immunizations. They may also be used for catch-up immunizations.

• Adjustments to the routine immunization schedule are needed for certain indications. ^[1][2]
• An overview of recommendations for vaccinating preterm infants, pregnant individuals, and those with HIV infection is detailed in this section.
• See “Immunization schedule by medical indication” and the latest CDC recommendations for adjustments in:
  • Patients with any of the following:
    • Altered immunocompetence (e.g., those with HIV, AIDS, asplenia, complement deficiencies) ^[32]
    • End-stage renal disease and those receiving hemodialysis
    • Heart disease
    • Lung disease
    • Chronic liver disease, alcohol use disorder
    • Diabetes
  • Health care personnel
  • Men who have sex with men

Immunizations in individuals with HIV ^[1][2][33]

• Inactivated vaccines are generally safe.
• If feasible, vaccination of individuals with HIV should be done before they become immunosuppressed.
• The immune response may be diminished if a vaccine is administered during a period of intense immunosuppression.
• See the latest CDC recommendations for details.

Exceptions to the routine immunization schedule

The routine ACIP immunization schedule is applicable to individuals with HIV with the following exceptions:

• Varicella vaccine, MMR vaccine, and dengue vaccines
  • Contraindicated in individuals with CD4 percentage < 15% or CD4 count 200 cells/mm³ or an AIDS-defining condition.
  • In individuals with CD4 ≥ 15% or 200 cells/mm³ for ≥ 6 months:
    • A 2-dose series of MMR is recommended for individuals with no evidence of immunity to MMR.
    • Use shared-decision making to determine the need for and schedule for varicella vaccine (in adults) and dengue vaccine.
• Influenza vaccine
  • Live attenuated influenza vaccine is contraindicated in all individuals with HIV.
  • Inactive influenza vaccine should be given instead.
• RZV ^[34]
  • 2 doses, 2–6 months apart (regardless of previous history of shingles)
  • Minimum age for first dose: ≥ 19 years of age
• HPV vaccine: Use a 3-dose series regardless of age at first immunization.
• Rotavirus vaccine: Use with caution in infants.
• Refer to the latest CDC recommendations for adjustments to the immunization schedule for: ^[33]
  • Pneumococcal vaccines
  • MenACWY vaccine ^[19]
  • Hib vaccine
  • COVID-19 vaccine

Live vaccines are contraindicated if CD4 count is < 200 cells/mm³ or CD4 percentage is < 15%. ^[1][2]

The efficacy of immunizations is reduced in individuals with HIV as a result of impaired immune function. ^[35]

Immunizations in preterm infants ^[36]

• Premature infants weighing < 2 kg at birth should receive the first HepB dose at 1 month or at hospital discharge, whichever is first. ^[2]
• Preterm infants should receive all other recommended vaccinations according to chronological age unless contraindicated.

Immunizations in pregnancy and lactation ^{[1][37][38][39]}

Prior to pregnancy ^[37][40]

• Recommend all routine age-appropriate immunizations.
• Annually assess immunization status for MMR, varicella, HepB, and Tdap ; ^[37][40][41]
  • Nonimmune women should receive appropriate vaccinations. ^[37]
  • If live vaccines are administered, advise individuals to avoid conceiving for 1–3 months. ^[37][42][43]
• Recommend current COVID-19 vaccination. ^[37]
• Recommend influenza vaccination (especially if pregnancy is expected during flu season). ^[37]

During pregnancy ^[1][37][38]

• For all pregnant individuals, recommend:
  • Tdap vaccine once every pregnancy, preferably at 27–36 weeks' gestation ^[37][38]
  • RSV vaccine (Abrysvo) between 32–36 weeks' gestation ^[44]
  • Inactivated influenza vaccine ; (IIV3 or RIV3) during flu season (safe in all trimesters) ^[37][45]
  • Current COVID-19 vaccination if not up to date
  • HepB vaccine if not previously vaccinated. ^[1][46]
• Consider additional immunizations based on risk factors, e.g.:
  • High-risk for HAV infection: HepA
  • High-risk for invasive meningococcal disease: meningococcal vaccines .
  • Certain travel vaccines
• Avoid contraindicated vaccines.
  • Live attenuated vaccines are contraindicated as they carry a theoretical risk of fetal infection (e.g., congenital rubella syndrome; , congenital varicella syndrome). ^{[20][37][38][40]}
  • Vaccines lacking safety data in pregnant individuals: HPV vaccine, RZV, certain HepB formulations (i.e., Heplisav-B and PreHevbrio) ^[38][47]

MMR vaccine, varicella vaccine, HPV vaccine, and live attenuated influenza vaccine are not recommended during pregnancy. ^[1][2]

After pregnancy and/or during lactation ^[37]

Lactation is not a contraindication for most vaccines.

• If live attenuated vaccines were deferred during pregnancy, administer them postpartum.
• Contraindicated: smallpox vaccine ^[39]
• Avoid the yellow fever vaccine unless the benefits outweigh the risks.

Women who lack immunity to rubella and/or varicella on prenatal screening (see “Prenatal care”) should be vaccinated postpartum.

Always consider if the benefits of immunization outweigh the risks during pregnancy and lactation; check contraindications. ^[40]

Immunizations for health care personnel (HCP) ^[48][49]

The following immunizations are an essential part of minimizing the risk of occupational exposure to and transmission of vaccine-preventable diseases in HCP.

Vaccine recommendations for all HCP ^[49][50]

• All HCP should receive routine and catch-up vaccinations according to the ACIP immunization schedule.
• In HCP who do not have evidence of pathogen-specific immunity , the following vaccines are recommended:
  • Hepatitis B vaccine; followed by post-vaccination serology 1–2 months after the last dose
  • Annual influenza vaccine
  • MMR vaccine
  • Varicella vaccine
  • One-time Tdap (if not previously administered); followed by Tdap or Td boosters every 10 years
  • COVID-19 vaccines

Additional vaccines in high-risk groups ^[48][50]

• Individuals with altered immunocompetence ^[1][2][48]
  • Additional vaccinations and/or boosters may be required, including:
    • Pneumococcal vaccine
    • Meningococcal vaccines
    • Hib vaccine
  • See “Immunization schedule by medical indication” for details.
• HCP who work with individuals at risk for HAV infection : Hepatitis A vaccine is recommended.
• Laboratory workers who handle highly infectious pathogens: Additional vaccinations and/or boosters against specific pathogens are recommended.
• HCP planning travel abroad: Relevant travel vaccinations should be completed prior to travel.

Verify immunization requirements with the local occupational health department.

Immunizations in men who have sex with men ^[1][51][52]

• Compared to other forms of unprotected sex, unprotected anal sex has the highest risk of HIV transmission. ^[51][53]
• Routine and catch-up vaccinations should be given according to the ACIP immunization schedule, especially:
  • Hepatitis A vaccine, hepatitis B vaccine
  • HPV vaccine
• Individuals with additional risk factors, e.g., immunosuppression due to HIV
  • Adjustments to the immunization schedule may be required.
  • See “Immunization schedule by medical indication” for details.

Approach ^[54]

• Ensure individuals are up to date on age-appropriate immunizations; see ACIP immunization schedule.
• If not already received, recommend the following routine immunizations before departure:
  • HepA vaccine and HepB vaccine
    • Infants 6–11 months of age: 1 dose of HepA vaccine before international travel (does not count toward routine immunization)
    • Adults: accelerated 3-dose series of HepA-HepB vaccine, followed by a booster at 12 months
  • MMR vaccine
    • Infants 6–11 months of age: 1 dose of MMR (does not count toward routine immunization.)
    • Children ≥ 12 months of age: 2-dose series of MMR or MMRV (counts toward routine immunization).
  • Influenza vaccine ≥ 2 weeks before travel if traveling to areas with influenza activity ^[55]
• Based on travel destinations (see the CDC's Travelers' Health website in “Tips and links”):
  • Administer any additional immunizations required.
  • Prescribe prophylactic medications as necessary (e.g., malaria prophylaxis).
• Consider additional protective measures, e.g.:
  • Prescribing medication that may be required (e.g., antibiotics to treat travelers' diarrhea)
  • Counseling on mosquito bite prevention and altitude-related disorders

Immunizations are not effective immediately, and certain malaria prophylaxis must be initiated 1–2 weeks before traveling to high-risk areas. ^[54][56]

Overview of additional immunizations before travel

This table provides an overview of the pretravel immunizations recommended for individuals from the United States who are planning international travel.