Understanding and Application of CDC Immunization Guidelines

Issues of Concern

ACIP Recommendation and CDC Immunization Schedule

A schedule is a tool that helps to shield individuals from disease by vaccinating them when they are the most vulnerable. The ACIP (Advisory Committee on Immunization Practices) recommends immunization in the United States.[5] After the CDC director reviews and approves the ACIP recommendation, they are published in MMWR (Morbidity and Mortality weekly report) as the final CDC recommendations for immunization in the United States.[6]

Annual Updates in the CDC Immunization Schedule 

CDC issues annual updates in immunization schedules.[7] New vaccines were added in some of the annual updates, eg, Chickenpox (1996), hepatitis A (2000), pneumococcal vaccine (2001). Few vaccines were discontinued from the schedule, eg, the oral polio vaccine (2004). New versions of existing vaccines were added, eg, DTaP (1997), intranasal influenza (2004). Additional recommendations were advised for already existing vaccines. The current immunization schedules for children below 6 years comprises vaccines that prevent 14 infectious diseases, which is a drastic achievement compared with the schedule in 1948 when immunizations against only diphtheria, tetanus, pertussis, and smallpox were available. Per the immunization schedule, a child may receive up to 24 injections in the first 2 years of age and up to 5 injections in a single visit.

2020 CDC Immunization Schedule Updates

The 2020 immunization schedule includes several updates and additions. The changes in the child immunization schedule are summarized as follows:

• Catch-up vaccination for Haemophilus influenza is not recommended for previously unvaccinated children above 5 years of age without risk factors.
• The catch-up immunization for Hepatitis A vaccine is recommended for all unvaccinated individuals aged 2 to 18.
• CDC 2020 recommends booster doses for Meningococcal B for persons above 10 years with risk factors like asplenia, complement deficiency, and microbiologists.
• Oral Polio Vaccine (OPV) doses may be counted toward the United States vaccination requirements. The OPV administered before April 1, 2016, should be counted.
• The 5th dose of the DTaP vaccine is unnecessary if the fourth dose was given after 4 years of age and 6 months after the third dose. 
• If a DTaP or Tdap vaccine is given at 10 years of age for other reasons, it can be included as the booster dose in the CDC schedule. If the DTaP or Tdap vaccine is given at 7 to 9 years of age, we should not include it as the booster dose, and Tdap should be readministered at eleven to twelve years of age. 

The changes in the Adult immunization schedule are summarized as follows:

• The age group 19 to 21 years and 22 to 26 years are combined as 19 to 26 years in the 2020 CDC schedule due to the change in the recommendation of catch-up HPV vaccination for all individuals aged up to 26. 
• A blue color box in the 2020 CDC schedule indicates shared clinical decision-making about vaccination for human papillomavirus vaccine, pneumococcal conjugate vaccine, and meningococcal B vaccine.
• Catch-up vaccination for diphtheria or tetanus after the first dose of Tdap can be given as Tdap or Td. Tdap can be used wherever only Td vaccine is indicated, eg, tetanus prophylaxis after wound management.
• CDC 2000 schedule recommends the HPV vaccine for individuals 11 to 26 years of age, irrespective of gender. Catch-up HPV vaccination is recommended for those not fully vaccinated up to 26. For individuals between 27 and 45 years, shared decision-making for the HPV vaccine is recommended. 
• Shared clinical decision-making is advised for PCV13 vaccination for healthy elderly individuals above 65 without risk factors. 
• Few changes are made in Hepatitis A indications for adults. HIV infection and persons experiencing homelessness are added to the existing list. Clotting factor disorders are removed from the list. 
• CDC recommends shared clinical decisions for the following, 
1. Meningococcal B vaccination for 16 to 23 years
2. HPV vaccine for 27 to 45 years 
3. PCV13 is for elderly individuals over 65 years old without risk factors.

Clinical Significance

CDC recommendations in the United States currently target 17 vaccine-preventable diseases throughout their lifetime. Ten vaccines covering 14 infectious diseases are targeted for children up to 10 years. They include diphtheria, tetanus, acellular pertussis (DTaP) vaccine, Haemophilus influenza type b vaccine, measles, mumps, and rubella vaccine (MMR), varicella vaccine, pneumococcal conjugate vaccine, inactivated poliovirus vaccine, rotavirus vaccine, hepatitis A vaccine, hepatitis B vaccine, and inactivated influenza vaccine. Four vaccines covering 6 infectious diseases are targeted for adolescents. They include Tetanus, Diphtheria acellular pertussis (Tdap), meningococcal conjugate, Human Papillomavirus, and the influenza vaccine.

DTaP (Diphtheria, Tetanus, acellular Pertussis) Vaccine 

• The minimum age for the DTaP vaccine is 6 weeks. 
• Per CDC guidelines, 5 dose series is necessary for DTaP at 2, 4, 6, 15-18 months, and 4 -6 years.
• The fifth dose is unnecessary for catch-up immunization if the fourth dose is given at more than 4 years of age and at least 6 months after the third dose. 
• DTaP is not recommended beyond 7 years of age. Tdap vaccine is preferred for kids after 7 years of age. 

Tdap (Tetanus, diphtheria, acellular pertussis) Vaccine 

• Tdap vaccine is administered at ages 11 to 12 and every 10 years. 
• Also, Tdap is recommended during each pregnancy between 27 to 36 weeks gestational. 
• Unvaccinated children above 7 years need 3 doses of Tdap with 4 weeks intervals between the first 2 doses and 6 months between the second and third dose. 

Haemophilus Influenza Type B (Hib) Vaccination 

• Six weeks is the minimum age for the Hib vaccine's first dose. 
• Four-dose series at 2, 4, 6, 12–15 months is recommended. 
• As per CDC guidelines, catch-up immunization for Hib in an unvaccinated kid is done as mentioned below,
• less than 6 months - 4 dose 
• 7-11 month - 3 doses; second dose at least 4 weeks from the first dose and the third dose at 12-15 months or 8 weeks after the second dose, whichever is later. 
• 12-14 months - 2 doses 8 weeks apart 
• 15- 59 months - 1 dose 
• more than 60 months without risk factors (healthy children) - no need for Hib vaccines 
• Special situations 
• Children undergoing elective splenectomy need 1 dose of Hib vaccine, preferably 14 days before the procedure, irrespective of vaccine status.
• Children who had stem cell transplants need 3 doses of Hib 4 weeks apart to be started 6 months after transplant, irrespective of vaccine status.
• Children under 5 years of age with risk factors for Hib infection need a similar schedule to the catch-up schedule. The risk factors include chemotherapy, radiation treatment, asplenia, sickle cell disease, immunoglobulin deficiency, early complement deficiency, and HIV infection. Unvaccinated persons from 5 -18 years with risk factors need 1 dose of Hib vaccine.

Hepatitis A Vaccination

• Twelve months is the minimum age for the first dose of the hepatitis A vaccine.
• A two-dose series is recommended with a 6-month interval, usually at 12 and 18 months.
• Catch-up immunization
• Unvaccinated individuals should complete a 2-dose series of Hepatitis A vaccine 6 months apart.
• Unimmunized children who have to travel to countries with high endemic hepatitis A virus should get 1 dose of the Hepatitis A vaccine before travel and the second dose after 6 months. For infants aged 6-12 months, 1 dose of Hep A vaccine should be given before travel and revaccination with 2 doses after 12 months. 
• Unimmunized children who had exposure to the hepatitis A virus need 1 dose of the Hepatitis A vaccine as post-exposure prophylaxis within 10 days of exposure. Children less than 12 months with exposure need immunoglobulin for post-exposure prophylaxis.

Hepatitis B Vaccination (HBV)

• Three dose series are recommended at 0, 1 to 2, and 6 to 18 months.
• All neonates above 2 Kg should get the first dose within 24 hours. For neonates under 2 Kg, the first dose can be given at 1 month or before discharge from the neonatal unit.
• If the neonate's mother has positive HBsAg, give the Hepatitis B vaccine and hepatitis B immune globulin within twelve hours. For infants under 2 Kg, an additional vaccine dose is needed at 1 month. At age 9 to 12 months, the infant should be tested for HBsAg and anti-HBs.
• If the maternal HBsAg result is unknown, give the Hepatitis B vaccine to the neonate within twelve hours of birth, irrespective of birth weight. The mother's HBsAg needs to be tested immediately. For infants less than 2 Kg, give Hepatitis B vaccine and Hepatitis B immune globulin within twelve hours. If the maternal HbSAg comes positive, Hepatitis B immune globulin must be given to neonates more than 2 Kg, as early as possible before 7 days of age.
• Catch-up vaccination: The 3-dose series can be started at any age for unvaccinated persons at 0, 1 to 2, or 6 months.

Human Papillomavirus Vaccination (HPV)

• Nine years is the minimum age for the first dose of the HPV vaccine.
• Routinely, the HPV vaccine is initiated at 11 to 12 years of age. For individuals with a history of sexual abuse, the first dose can be started at 9 years. 
• CDC recommends 2-dose series (0,6 months) for age groups up to 14 years and 3-dose series (0, 1, 6 months) for the 15 years and above age group.
• The catch-up HPV vaccination is recommended for all individuals aged up to 26.

Influenza Vaccination

• The minimum age for the influenza vaccine is 6 months for the inactivated vaccine and 2 years for the live vaccine. 
• For the age group 6 months to 8 years, 2 doses 4 weeks apart are recommended for those getting them for the first time. In subsequent years, kids up to 8 years can get only 1 dose annually. One dose is recommended for all individuals above 9 years of age.
• Individuals with egg allergies can get the influenza vaccine under medical supervision. 

Measles, Mumps, and Rubella Vaccination (MMR)

• Two doses are recommended at 12 to 15 months and 4 to 6 years.
• Twelve months is the minimum age for the first dose, and a 4-week minimum interval is needed between the first and second doses. 
• MMR vaccine can be given to children 6 to 11 months old who need to travel to countries with high endemicity for measles. However, this dose does not count toward the 2-dose series.  
• For unvaccinated individuals, 2 doses 4 weeks apart are recommended.
• MMR vaccine can be used as postexposure prophylaxis within 3 days of exposure. 

Poliovirus Vaccination (IPV)

• Six weeks is the minimum age for the first dose of IPV. 
• Four-dose series is administered at ages 2, 4, 6 to 18 months, and 4 to 6 years. 
• For unimmunized children, 4-dose series is recommended. The fourth dose is unnecessary if the 3rd dose is given after 4 years of age. IPV is not needed after 18 years of age.

Rotavirus Vaccination 

• Six weeks is the minimum age for the first dose of rotavirus. 
• Three dose series recommended at 2,,4 and 6 months for pentavalent rotavirus vaccine. A 2-dose series at 2 and 4 months is recommended if the monovalent rotavirus vaccine is administered. 
• The series should not be started after 15 weeks of age.
• The final dose should be administered before 8 months.

Varicella Vaccination 

• Twelve months is the minimum age for the first dose of varicella vaccine.
• Two doses are administered at 12 to 15 months and 4 to 6 years. The second dose may be given as early as 3 months after the 1st dose.
• Unimmunized children less than 12 years need 2 doses with 3 months interval. For individuals above 13 years, a 4-week interval is enough. 

Meningococcal Vaccine (serogroup A,C,W,Y vaccination)

• For all individuals, 2-dose series is recommended at 11 to 12 years and 16 years.
• For ages 13 to 15 years, 2 doses with 8 weeks minimum interval. The second dose should be after 16 years. 
• For age 16 to 18 years, only 1 dose is needed. 
• The risk factors for meningococcal infection are asplenia, sickle cell disease, complement component deficiency, and the use of eculizumab (complement inhibitor). 
• The minimum age for vaccination is 2 months for the MenACWY-CRM vaccine and 9 months for the MenACWY-D vaccine. 
• The menACWY-CRM vaccine is a 4-dose series at 2, 4, 6, and 12 -15 months. For the age group 7 to 23 months, a 2-dose series is recommended with a 12-week interval and a second dose given after 12 months. For kids aged more than 24 months, a 2-dose series with an 8-week interval is recommended. 
• The menACWY-D vaccine is given as a 2-dose series with 12-week intervals for 9 to 23 months age group and 8 weeks for more than 24 months age group. For kids with sickle cell disease, the MenACWY-D vaccine is administered after 24 months at least 4 weeks after completion of the PCV13 series.
• For individuals traveling to countries with an endemic meningococcal disease like Africa or during Hajj, the MenACWY-CRM vaccine or MenACWY-D vaccine is recommended with age-specific series, as explained before. 
• Unvaccinated first-year college students who live in residential housing or military recruits should get 1 dose of the MenACWY-CRM vaccine or the MenACWY-D vaccine.

Meningococcal Serogroup B Vaccination 

• The first dose's minimum age is 10 years for MenB-4C and MenB-FHbp vaccines. 
• Routine immunization is not necessary for all individuals. Adolescents aged 16 to 23 years without any risk factors can get vaccines based on shared clinical decision-making.
• The risk factors for meningococcal B infection are asplenia, sickle cell disease, complement component deficiency, and eculizumab (complement inhibitor). 
• The MenB-4C vaccine is given as a 2-dose series at least 1 month apart. The MenB-FHbp vaccine is a 3-dose series at 0, 1 to 2, and 5 months. 
• MenB-4C and MenB-FHbp vaccines are not interchangeable; the same product should be used for all doses in a series. 

Pneumococcal Vaccination 

• The minimum age is 6 weeks for pneumococcal conjugate vaccine-13 valent (PCV13) and 2 years for pneumococcal polysaccharide vaccine 23 valent (PPSV23).
• For routine immunization, the conjugate vaccine (PCV13) is used. A 4-dose series is recommended at 2, 4, 6, and 12 to 15 months. 
• For age groups 7 to 23 months, a 2-dose series is recommended with a 12 weeks interval and a second dose given after 12 months. For unimmunized healthy children aged 2 to 5 years, 1 dose is recommended. 
• PCV13 is not routinely recommended for healthy children above 5 years of age. 
• If PCV13 and PPSV23 need to be given, PCV13 is administered first. They should not be given together on the same day.
• For high-risk children of age group 2 to 5 years, a 2-dose series of PCV13 with 8 weeks intervals followed by 1 dose of PPSV23 at least 8 weeks after the last PCV13 dose. 
• For the 6-18 years age group,the  vaccine series is decided as per the underlying risk factors. 
1. Individuals with chronic cyanotic congenital heart disease, chronic liver disease, chronic asthma on high-dose steroids, and diabetes mellitus need 1 dose of PPSV23. They do not need a PCV13.
2. Individuals with a cerebrospinal fluid leak or cochlear implant need 1 dose of PCV13 followed by 1 dose of PPSV23 after 8 weeks.
3. Individuals with Sickle cell disease, asplenia, immunodeficiency, HIV infection, chronic renal failure, nephrotic syndromes, leukemias, lymphomas, and Hodgkin disease need 1 dose of PCV13 followed by 2 doses of PPSV23. The first dose of PPSV23 is administered 8 weeks after PCV13, and the second dose is administered at least 5 years after dose 1 of PPSV23.

Enhancing Healthcare Team Outcomes

Vaccine Coverage 

As per the 2020 CDC report, the USA's vaccination rate in 2019 was approximately 95% for MMR, Varicella, and DTaP.[8] In the 2018-2019 school year, the measles outbreak in several states proves the need to stress school vaccination requirements for all children. Apart from parental refusal, the providers' lack of understanding about contraindications to immunization and poor patient tracking across various healthcare venues are major contributing factors for the drop in immunization coverage.[9]  

Vaccine Noncompliance

The immunization rate among children entering kindergarten exceeds 90 percent for all the vaccines among kids entering kindergarten. Still, we can see the emergence of vaccine-preventable diseases due to increased vaccination delay and refusal. Measles and pertussis outbreaks happened in areas with low vaccination rates. Families refuse vaccines for medical, religious, philosophical, or socioeconomic reasons. Clinicians have a crucial role in parental decision-making for vaccination.[10] Patient counseling, improving access to vaccination, offering combination vaccines, and using vaccine delay alerts and reminder-recall systems incorporated in EMR help improve vaccine compliance.[11][12] 

Vaccination Recommendations During the COVID-19 Pandemic

As per the CDC, the COVID pandemic has reduced the immunization rate in the 2020-2021 school year among children entering kindergarten due to decreased slots for well-visit appointments and schools not enforcing the vaccination policies because of remote learning. Separate the well-visits from sick visits at different times of the day, identifying children who have missed well-child visits, and vaccination and reminders in EMR for missed immunization can improve vaccination rate during the COVID-19 pandemic.