Some days, vaccinations go as planned. A child comes in for a visit and receives the recommended vaccines. The provider’s review of the schedule and the electronic health record (EHR) agree on what is recommended, and the child has everything required for a given school or camp entry. However, with the complexity of the schedule, combination vaccines, and families that have altered the schedule, clinicians are now commonly trying to figure out if a specific dose “counts” or if a child is fully protected. School healthcare providers, a camp enrollment check, or even the EHR may flag a child as not “up to date.” When these events happen, clinicians will need to scrutinize the child’s schedule to determine if the child is adequately protected from infection.
As providers work through the following scenarios, it’s instructive to understand why the patient might not be adequately protected and determine what doses are needed to ensure the child is up to date. Occasionally, there may be extra communication with a school or camp on the nuance of a specific child’s record so that they are compliant with the organization’s needs and can participate. Let’s look at four tricky scenarios.
Scenario #1: Third dose of MMR needed?
A 5-year-old is starting kindergarten. They previously received two doses of MMR vaccine. One was given at 7 months of age when the family was traveling internationally to visit relatives. The second dose was given at the child’s 4-year-old well visit. The school has told the family that the child needs a third dose of vaccine. Is this additional dose needed?
Infants may receive a dose of MMR vaccine prior to their first birthday to travel abroad because they live in an outbreak region or as post-exposure prophylaxis. This dose, sometimes called “dose 0,” should not be counted as part of the child’s two-dose series. As described on the “Measles, Mumps and Rubella (MMR): The Diseases and Vaccines” webpage, the reason why is that at such a young age, the infant is likely to still have some maternal antibodies circulating, and these antibodies can interfere with development of the immune response to the vaccine. Therefore, when the child turns 1, they should get a dose, which would count as their first dose. The second dose can be administered 28 days (or more) after the valid first dose.
Scenario #2: Invalid varicella dose?
A 5-year-old child who recently entered kindergarten received his first doses of MMR and varicella vaccines in mid-August, as a dose of MMRV. They returned to the office exactly 28 days after that dose, eager to get the second dose of MMR because of a current measles outbreak in the area. On this second visit, the child was given MMRV again. The school nurse received the updated vaccine form and told the family that the varicella dose is invalid and needs to be repeated. Is this additional dose needed?
The recommended interval between two doses of varicella is three months for children younger than 13 years of age. This is based on data from the clinical trials which demonstrated that two doses of vaccine spaced three months apart was greater than 98% effective at preventing any disease, and 100% effective against severe disease. Most studies evaluating a single dose of varicella vaccine demonstrate effectiveness between 80%-89% against preventing disease, so the two-dose regimen was superior. Based on the clinical trial design, a three-month interval between doses of varicella vaccine has been the recommended regimen since 2007, when a second dose became standard.
However, subsequent immunogenicity studies have demonstrated that individuals vaccinated with just a one-month interval also have an effective immune response. Because of these additional studies, the second MMRV dose is a valid second dose for all four pathogens in the above scenario. As such, the family can be reassured that doses separated by just 28 days are biologically effective, and their child has sufficient protection. Clinicians can help support this family by providing additional documentation to the school, so the child is considered compliant.
Scenario #3: Additional dose of RSV monoclonal antibody?
A 3-month-old infant entering their first RSV season comes in for their dose of nirsevimab. They weigh 5.3 kg (11.7 pounds). The person administering the monoclonal antibody uses the weight recorded at the last well baby visit of 4.7 kg and administers 50 mg of nirsevimab. The family leaves the office, and when the infant returns for the 6-month visit, the provider realizes that the child was underdosed. Does the 50 mg dose count?
If a half dose was inadvertently given, another half dose should be administered as soon as possible. The American Academy of Pediatrics has a page that addresses this, “RSV Immunization Administration Frequently Asked Questions.” Nirsevimab, a monoclonal antibody, was studied as a weight-based dose to ensure that children receive appropriate protection as they grow. Since this child should have received 100 mg, it is appropriate to give the additional 50 mg at this visit. Given that this product delivers passive protection in the form of antibodies that will circulate, the child does not need to repeat the full dose of 100 mg.
One note is that this may create a billing discrepancy with the insurance company, which may see this as two different administrations. The office should work to remedy this, so the family isn’t left with additional costs resulting from the dosing error.
Scenario #4: Another dose of Tdap?
An 8-year-old patient received doses of DTaP vaccine at 2 and 5 years of age. He then received a Tdap vaccine a few weeks after turning 7. Does this Tdap bring him up to date, or does he need one more dose?
The dosing is atypical, but the child is effectively protected. Ideally, a child receives five doses of DTaP as their primary series. Early in life, the 2-, 4-, and 6-month doses are primary doses that build immunity. The fourth and fifth doses are booster doses that remind the immune system of these pathogens.
Table 2 of the AAP Catch-Up Immunization Schedule provides some clarity. Children over 7 years of age who are catching up on tetanus-, diphtheria- and pertussis-containing vaccines should have three doses with Tdap serving as the final dose as long as the first dose of a relevant vaccine was administered on or after the first birthday. The Centers for Disease Control and Prevention (CDC) has two job aids that can help with these complex issues — one for children 7-9 years of age and another for children 10-18 years of age.
Wrap-up
Dosing questions can be complicated and not easily determined by quickly looking at the schedule. Luckily, resources are available to help. Bookmark this article or the resources listed below, so you can easily get answers when you need them.
- AAP Immunization FAQs
- ACOG Tools and Resources
- Ask the Experts (Immunize.org)
- The Vaccine Handbook: A Practical Guide for Clinicians
You can also always contact us at the Vaccine Education Center for additional support navigating challenging scenarios. While we cannot offer patient-specific advice via email, we can answer general questions, such as those presented in the scenarios.
Some days, vaccinations go as planned. A child comes in for a visit and receives the recommended vaccines. The provider’s review of the schedule and the electronic health record (EHR) agree on what is recommended, and the child has everything required for a given school or camp entry. However, with the complexity of the schedule, combination vaccines, and families that have altered the schedule, clinicians are now commonly trying to figure out if a specific dose “counts” or if a child is fully protected. School healthcare providers, a camp enrollment check, or even the EHR may flag a child as not “up to date.” When these events happen, clinicians will need to scrutinize the child’s schedule to determine if the child is adequately protected from infection.
As providers work through the following scenarios, it’s instructive to understand why the patient might not be adequately protected and determine what doses are needed to ensure the child is up to date. Occasionally, there may be extra communication with a school or camp on the nuance of a specific child’s record so that they are compliant with the organization’s needs and can participate. Let’s look at four tricky scenarios.
Scenario #1: Third dose of MMR needed?
A 5-year-old is starting kindergarten. They previously received two doses of MMR vaccine. One was given at 7 months of age when the family was traveling internationally to visit relatives. The second dose was given at the child’s 4-year-old well visit. The school has told the family that the child needs a third dose of vaccine. Is this additional dose needed?
Infants may receive a dose of MMR vaccine prior to their first birthday to travel abroad because they live in an outbreak region or as post-exposure prophylaxis. This dose, sometimes called “dose 0,” should not be counted as part of the child’s two-dose series. As described on the “Measles, Mumps and Rubella (MMR): The Diseases and Vaccines” webpage, the reason why is that at such a young age, the infant is likely to still have some maternal antibodies circulating, and these antibodies can interfere with development of the immune response to the vaccine. Therefore, when the child turns 1, they should get a dose, which would count as their first dose. The second dose can be administered 28 days (or more) after the valid first dose.
Scenario #2: Invalid varicella dose?
A 5-year-old child who recently entered kindergarten received his first doses of MMR and varicella vaccines in mid-August, as a dose of MMRV. They returned to the office exactly 28 days after that dose, eager to get the second dose of MMR because of a current measles outbreak in the area. On this second visit, the child was given MMRV again. The school nurse received the updated vaccine form and told the family that the varicella dose is invalid and needs to be repeated. Is this additional dose needed?
The recommended interval between two doses of varicella is three months for children younger than 13 years of age. This is based on data from the clinical trials which demonstrated that two doses of vaccine spaced three months apart was greater than 98% effective at preventing any disease, and 100% effective against severe disease. Most studies evaluating a single dose of varicella vaccine demonstrate effectiveness between 80%-89% against preventing disease, so the two-dose regimen was superior. Based on the clinical trial design, a three-month interval between doses of varicella vaccine has been the recommended regimen since 2007, when a second dose became standard.
However, subsequent immunogenicity studies have demonstrated that individuals vaccinated with just a one-month interval also have an effective immune response. Because of these additional studies, the second MMRV dose is a valid second dose for all four pathogens in the above scenario. As such, the family can be reassured that doses separated by just 28 days are biologically effective, and their child has sufficient protection. Clinicians can help support this family by providing additional documentation to the school, so the child is considered compliant.
Scenario #3: Additional dose of RSV monoclonal antibody?
A 3-month-old infant entering their first RSV season comes in for their dose of nirsevimab. They weigh 5.3 kg (11.7 pounds). The person administering the monoclonal antibody uses the weight recorded at the last well baby visit of 4.7 kg and administers 50 mg of nirsevimab. The family leaves the office, and when the infant returns for the 6-month visit, the provider realizes that the child was underdosed. Does the 50 mg dose count?
If a half dose was inadvertently given, another half dose should be administered as soon as possible. The American Academy of Pediatrics has a page that addresses this, “RSV Immunization Administration Frequently Asked Questions.” Nirsevimab, a monoclonal antibody, was studied as a weight-based dose to ensure that children receive appropriate protection as they grow. Since this child should have received 100 mg, it is appropriate to give the additional 50 mg at this visit. Given that this product delivers passive protection in the form of antibodies that will circulate, the child does not need to repeat the full dose of 100 mg.
One note is that this may create a billing discrepancy with the insurance company, which may see this as two different administrations. The office should work to remedy this, so the family isn’t left with additional costs resulting from the dosing error.
Scenario #4: Another dose of Tdap?
An 8-year-old patient received doses of DTaP vaccine at 2 and 5 years of age. He then received a Tdap vaccine a few weeks after turning 7. Does this Tdap bring him up to date, or does he need one more dose?
The dosing is atypical, but the child is effectively protected. Ideally, a child receives five doses of DTaP as their primary series. Early in life, the 2-, 4-, and 6-month doses are primary doses that build immunity. The fourth and fifth doses are booster doses that remind the immune system of these pathogens.
Table 2 of the AAP Catch-Up Immunization Schedule provides some clarity. Children over 7 years of age who are catching up on tetanus-, diphtheria- and pertussis-containing vaccines should have three doses with Tdap serving as the final dose as long as the first dose of a relevant vaccine was administered on or after the first birthday. The Centers for Disease Control and Prevention (CDC) has two job aids that can help with these complex issues — one for children 7-9 years of age and another for children 10-18 years of age.
Wrap-up
Dosing questions can be complicated and not easily determined by quickly looking at the schedule. Luckily, resources are available to help. Bookmark this article or the resources listed below, so you can easily get answers when you need them.
- AAP Immunization FAQs
- ACOG Tools and Resources
- Ask the Experts (Immunize.org)
- The Vaccine Handbook: A Practical Guide for Clinicians
You can also always contact us at the Vaccine Education Center for additional support navigating challenging scenarios. While we cannot offer patient-specific advice via email, we can answer general questions, such as those presented in the scenarios.