US Pharm. 2021;46(6):10-12.
Immunization, a process by which a person becomes protected against an infectious disease through vaccination, is one of the most effective preventive health measures. Vaccination is the act of introducing a vaccine into the body to produce immunity to a specific disease. Immunization is often used interchangeably with vaccination or inoculation.1
Immunity acquired through immunization is similar to the immunity a person would obtain from a disease itself, but through a vaccine instead of the disease. Most vaccines are given through IM injection, but some are given orally or nasally.1
When a person is vaccinated, the body responds as though it has been infected with the disease and makes antibodies as a result. These antibodies stay in the body for extended periods of time and memorize how to fight the pathogen. In the future, if the disease enters the body, the antibodies destroy the pathogens before the person can become sick. Because vaccines contain weakened or inactive parts of a particular organism, they are much safer than getting the actual disease.1
Most people are fully protected against a disease after getting immunized. In rare cases, people who are immunized can still get the disease because they get only partial protection from the vaccine. This is more common in people with medical conditions that affect the immune system. Although these people may still get the disease, they will most likely get a milder illness and not suffer serious complications.1
The number of cases of most vaccine-preventable illnesses in the United States has declined by more than 90% since routine childhood immunizations were introduced.2,3
Immunization Types and Schedules
Routine immunization schedules vary by country. In the U.S., routine immunization schedules for children and adolescents are updated annually and collaboratively by the CDC and the Advisory Committee on Immunization Practices (ACIP), the Committee on Infectious Diseases of the American Academy of Pediatrics, the American Academy of Family Physicians, the American College of Obstetricians and Gynecologists, and the American College of Nurse-Midwives.2,3
Vaccination programs directly benefit immunized individuals. However, they also indirectly benefit unimmunized persons through herd immunity. Community or herd immunity occurs when the portion of the population that is immune to the infection is large enough to decrease the risk of transmission. Herd immunity protects children who are too young for immunization and persons with contraindications to vaccines. It relies on the majority of the population receiving routinely recommended immunizations.4
Failure to adhere to the recommended immunization schedules by healthcare providers, parents, and other caregivers, including the timing of immunizations, leaves children susceptible to life-threatening, vaccine-preventable diseases.4
Immunization of Infants and Children
Immunizations that are routinely recommended for infants and children in the U.S. are usually administered at the hospital or at clinic visits. However, every visit provides an opportunity to update vaccines. Multiple injections are required at most visits. The use of combination vaccines, e.g., diphtheria; tetanus; acellular pertussis (DTaP); measles, mumps, and rubella (MMR); MMR and varicella (ProQuad); and many other combinations can help to reduce the number of injections at each visit and improve immunization coverage for several diseases.3,5
The immunizations routinely recommended for infants and children in the U.S. are as follows3,6:
Hepatitis B Vaccine (HepB): HepB vaccine is routinely recommended within 24 hours of birth, at ages 1 through 2 months, and at ages 6 through 12 months. HepB vaccine is inactivated and is administered IM.
Rotavirus Vaccine: The routine schedule for rotavirus vaccine depends upon the vaccine formulation. The pentavalent human-bovine rotavirus reassortant vaccine (RV5) is administered at ages 2, 4, and 6 months. The attenuated human rotavirus vaccine (RV1) is administered at ages 2 and 4 months. Both rotavirus vaccines are live, attenuated viral vaccines. They are administered orally.
Diphtheria, Tetanus, and/or Pertussis Vaccine: DTaP vaccine is routinely recommended for infants and children at ages 2 months, 4 months, 6 months, 15 through 18 months, and 4 through 6 years. Booster doses are required beginning at age 11 years. DTaP vaccine is an inactivated vaccine and is administered IM.
Haemophilus influenzae Type B Conjugate Vaccine (Hib): Hib conjugate vaccine is routinely recommended in a two- or three-dose primary series (at ages 2 and 4 months, or ages 2, 4, and 6 months, depending upon the vaccine formulation) with a booster dose at ages 12 through 15 months. Hib vaccines are inactivated vaccines and are administered IM.
Pneumococcal Conjugate Vaccine: The 13-valent pneumococcal conjugate vaccine (PCV13) is routinely recommended at 2, 4, 6, and 12 through 15 months of age. PCV13 is an inactivated vaccine and is administered IM.
Inactivated Poliovirus Vaccine (IPV): IPV is routinely recommended at 2 months, 4 months, 6 through 18 months, and 4 through 6 years of age. IPV is administered IM or SC.
Influenza Vaccine: Influenza immunization is recommended annually for all children aged 6 months and older, particularly those at high risk for complications. Inactivated influenza vaccines (IIV) for children under age 18 years are administered IM. The live attenuated influenza vaccine (LAIV) is administered intranasally.
Measles, Mumps, and Rubella Vaccine: MMR vaccine is routinely recommended at ages 12 through 15 months and ages 4 through 6 years. MMR is a live attenuated virus vaccine and is administered SC.
Varicella Vaccine: Varicella-zoster virus (VZV; chickenpox) vaccine is routinely recommended at ages 12 through 15 months and ages 4 through 6 years. VZV vaccine is a live attenuated virus vaccine. It is stored frozen and is administered SC.
Hepatitis A Vaccine: Two doses of hepatitis A virus (HepA) vaccine are routinely recommended between ages 12 and 24 months; the doses should be separated by at least 6 months. HepA vaccine is an inactivated vaccine. It is administered IM.
Immunity of Adolescents
Most of the immunizations that are routinely recommended for adolescents in the U.S. are administered at ages 11 through 12 years or age 16 years. However, every healthcare visit provides an opportunity to update and/or complete an adolescent’s immunizations. Immunizations that are routinely recommended for adolescents in the U.S. are as follows3,6,7:
Tetanus, Diphtheria, and Acellular Pertussis (Tdap): A dose of Tdap vaccine is routinely recommended at ages 11 through 12 years. Tdap is an inactivated vaccine and is administered IM.
Meningococcal Vaccine: Quadrivalent meningococcal conjugate vaccine is routinely recommended at ages 11 through 12 years and at age 16 years. This is an inactivated vaccine and is administered IM.
Human Papillomavirus Vaccine: Two doses of the 9-valent human papillomavirus (HPV) vaccine are routinely recommended for immune-competent adolescents 11 through 12 years of age; the doses should be separated by at least 6 months.
If the adolescent is immunocompromised or the HPV vaccine series is initiated at age 5 years and older, three doses of HPV vaccine are recommended; the second dose should be given 1 to 2 months after the first dose; the third dose should be given 6 months after the first dose.
Influenza Vaccine: Influenza immunization is recommended annually for all children aged 6 months and older, particularly those at high risk for complications. IIV vaccines for children are administered IM. LAIV is administered intranasally.
Vaccine Hesitancy or Refusal: Despite being recognized as one of the most successful public health measures, vaccination is perceived as unsafe and unnecessary by a growing number of parents. Antivaccination movements have resulted in lowered vaccine acceptance rates and in recent, localized increases in vaccine-preventable disease outbreaks and epidemics.2,3,8
Unknown Immunization Record: For children with unknown or uncertain immunization records, serologic testing for antibodies to vaccine-preventable illnesses, revaccinating (as if the child were unvaccinated), or a combination of the two approaches is reasonable. The CDC ACIP generally recommends age-appropriate revaccination.2,3,8
Preterm Infants: The routine immunization schedule, dose, intervals, and contraindications/precautions are the same for preterm infants (born at <37 weeks’ gestation) as for infants and children who were born at 37 weeks’ gestation or later, with the exception of the HepB vaccine. For infants who weigh less than 2 kg (4.4 pounds) at birth and are born to women who are hepatitis B surface-antigen negative, the first dose of HepB vaccine is postponed until hospital discharge or age 30 days, whichever comes first.2,3,8
Close Contacts of Immunocompromised Persons: Close (e.g., household/family) contacts of immunocompromised persons should receive all routinely recommended vaccines. Close contacts of immunocompromised persons should not receive the smallpox vaccine as it is not routinely recommended for children or adolescents.2,3,8
Children and Adolescents With Increased Risk of Bleeding: Children and adolescents at increased risk of bleeding following IM injections should consult a hematologist. The ACIP best-practice guidelines indicate that IM injections can be administered to a child or adolescent with a bleeding disorder if a clinician familiar with the patient’s bleeding risk determines that the vaccine can be administered with reasonable safety.2,3,8
If possible, IM injections should be scheduled shortly after administration of clotting factors or before administration of anticoagulant medications using a 23-gauge or smaller caliber needle. Firm pressure should be applied on the site, without rubbing, for at least 2 minutes after injection.2,3,8
Pregnant Adolescents: Live vaccines (e.g., MMR vaccine, varicella vaccine, and HPV vaccine) should be avoided during pregnancy.2,3,8
Children or Close Contacts of Pregnant Women: Children and close contacts of pregnant women should receive routinely recommended vaccines, including live virus vaccines (e.g., MMR vaccine, varicella vaccine, rotavirus vaccine).2,3,8
Recent or Anticipated Administration of Immune Globulin or Blood Products: MMR and varicella vaccines should not be administered on the same day as immune globulin or for several months after immune globulin or blood products. Immune globulin and blood products contain antibodies, which can interfere with the vaccine response.
If immune globulin or blood products must be given within 14 days after administration of MMR or varicella vaccine, another dose of the vaccine should be administered after the suggested interval.2,3,8
Correct vaccine administration is critical to ensure that vaccination is safe and effective. The CDC recommends that all healthcare personnel who administer vaccines receive comprehensive, competency-based training on vaccine-administration policies and procedures before administering vaccines. The ACIP provides best practice recommendations for vaccine administration, including minimum ages and intervals between vaccine doses.2,9
Generally, immunizations need to be administered according to the “seven rights”: the right patient, the right vaccine or diluent, the right time, the right dosage, the right route and needle length, the right site, and the right documentation.9 Variations from these recommendations may result in invalid doses and lack of coverage.
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1. CDC. General best practice guidelines for immunization: best practices guidance of the Advisory Committee on Immunization Practices (ACIP). Vaccination programs. www.cdc.gov/vaccines/hcp/acip-recs/general-recs/programs.html. Accessed April 4, 2021.
2. CDC. Immunization schedules. www.cdc.gov/vaccines/schedules/index.html. Accessed May 6, 2021.
3. Drutz JE. Standard immunization for children and adolescents: overview. Updated December 8, 2020. www.uptodate.com/contents/standard-immunizations-for-children-and-adolescents-overview. UpToDate, Inc. Accessed April 4, 2021.
4. Meissner HC. Why is herd immunity so important? AAP News. 2015;36:14.
5. Marshall GS, Happe LE, Lunacsek OE, et al. Use of combination vaccines is associated with improved coverage rates. Pediatr Infect Dis J. 2007;26:496-500.
6. Pickering LK, Baker CJ, Freed GL, et al. Immunization programs for infants, children, adolescents, and adults: clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis. 2009;49:817-840.
7. Society for Adolescent Health and Medicine. Establishing an immunization platform for 16-year-olds in the United States. J Adolesc Health. 2017;60:475-476.
8. CDC. Special situations. www.cdc.gov/vaccines/hcp/acip-recs/general-recs/special-situations.pdf. Accessed May 6, 2021.
9. American Academy of Pediatrics. Vaccine administration. In: Red Book: 2018 Report of the Committee on Infectious Diseases, 31st ed. Kimberlin DW, Brady MT, Jackson MA, Long SS, eds. Itasca, IL: American Academy of Pediatrics, 2018, p.26.
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