Every once in a while we see a child whose school nurse says the child’s vaccines didn’t count and need to be repeated. This can be due to many things, usually inappropriate timing of vaccines. Some electronic health records now have intelligent vaccine recommendation abilities. These smart vaccine logic systems are catching kids who had incorrect spacing before this technology. Staying on the routine vaccine schedule and keeping all records in one place can help avoid extra doses due to inappropriately spaced vaccines.
One thing to remember if your child needs extra doses: you don’t need to worry. They’re safe!
What’s in this post?
First you’ll need to understand about the different types of vaccines to know why they are scheduled like they are. Some are given in a series to boost the initial response, but others need to be repeated to cover those who weren’t protected with a first dose.
Then we’ll do a quick review of the risk of the diseases to remind us why we vaccinate in the first place.
Hopefully after learning some basics, you’ll see why the timing of vaccines is so important and why we should all follow the recommended vaccine schedule.
What’s not in this post?
If you want to know what to do if a recommended vaccine has been delayed, see What happens if a vaccine booster is delayed?
Dr. Vincent Iannelli has a list that includes some issues not discussed in this post, such as improper storage.
How vaccines work
Vaccines are made in different ways and the body responds to them in different ways.
Live attenuated vaccines
Live attenuated vaccines are made from weakened virus that teaches the body to recognize the real virus but doesn’t cause the symptoms of the virus in healthy people.
Those with weak immune systems should talk to their physician before receiving a live virus vaccine. The amount of immune compromise and specific vaccine must be taken into account on an individual basis.
It’s usually okay to be vaccinated with a live virus vaccine if you’ll be around an immunocompromised person, but again, let your physician know the risk of exposure.
Examples of live virus vaccine:
- rotavirus
- measles
- mumps
- rubella
- varicella
- nasal flu vaccine (NOT the injectable flu vaccine)
Many people respond sufficiently to the first dose of these, but repeat doses are given to help those who missed the response the first time.
The second dose doesn’t boost the first, but it gives a person a second chance at making immunity.
Spacing between doses:
Because of the way these vaccines work, they must follow special separation rules. More than one live virus vaccine can be given on the same day, but they cannot be given on separate days that are closer than 4 weeks apart.
If one live virus vaccine is given, you must wait a minimum of 28 days to give another. If they’re given too close together, the body doesn’t make immunity as well to the second one given. This second vaccine wouldn’t count.
As an example, if the FluMist (nasal flu vaccine) is given on January 1 and the Varicella vaccine is given January 15 of the same year, the Varicella vaccine will not count and must be repeated.
Live virus vaccines are the only vaccines that are subject to this 28 day rule. If another vaccine type is needed, it is okay to give in a shorter time frame.
For example, if a child has the MMR at his 4 year well visit, it is okay to do an injectable flu vaccine at a flu clinic later that same month. (Note: the nasal flu vaccine is a live virus vaccine, so it is NOT okay to give the FluMist within the month before or after the MMR.)
If there is less than 28 days between live virus vaccines, the one that was given second must be repeated.
I see this quite frequently in kids who move to the US from other countries. It seems quite common elsewhere for kids to get the varicella (chicken pox) vaccine about 2 weeks after the MMR. When this happens, another varicella vaccine is needed.
Live virus vaccines aren’t recommended under 1 year… usually
Many parents worry that we don’t give live virus vaccines to infants because they’re less safe, but that’s not why at all.
Maternal antibodies (fighter cells from mom that got into baby during pregnancy) can inhibit the body from being able to build its own antibodies well against a vaccine.
Maternal antibodies are good because as long as they’re in the baby’s body, they fight off germs and protect the infant! They tend to hang around for the first 6-12 months of life.
If a disease has a low incidence, it is acceptable to let the maternal antibodies do their job for the first year.
By the first birthday most maternal antibodies have left the infant, so a vaccine can be used to build the baby’s immunity.
International travel increases risks
If there is a high risk of exposure it is recommended to give the vaccine as early as 6 months in case the maternal antibodies are already too low for infant protection. Many parts of the world have high measles rates so fit into this recommendation.
If the antibody levels are still high, the vaccine won’t work, but the baby should still be protected against the disease from mom’s antibodies.
At some point the maternal antibodies go away, we just don’t know when exactly, so the baby who gets the MMR early needs another dose after his first birthday to be sure he’s making his own antibodies once mom’s go away. This dose after the birthday is the first that “counts” toward the two MMRs that are needed.
The next dose of MMR can be anytime at least 28 days after the first counted dose, but we traditionally give it between 4-6 years with the kindergarten shots.
Yes, I realize there are some measles outbreaks in the US, but the experts have not said to start giving that extra dose to babies who are staying here yet. If you’re worried, talk to your doctor.
Inactivated virus vaccines
Inactivated virus vaccines are made by killing the virus and using it to make the vaccine.
They aren’t as effective as live virus vaccines, so several doses are needed to build immunity to these.
Examples of inactivated virus vaccines:
- inactivated polio vaccine
- injectable flu vaccines
- hepatitis A vaccine
Subunit, recombinant, polysaccharide, and conjugate vaccines
Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of a virus or bacteria to make a vaccine.
Because these vaccines use only specific antigens, they give a very strong immune response that’s specific to the infectious particle and side effects are less common.
This type of vaccine is safe for nearly everyone, including people with weak immune systems.
One limitation of these vaccines is that you may need booster shots to get ongoing protection against diseases.
Subunit, recombinant, polysaccharide, and conjugate vaccines include:
- Hib (Haemophilus influenzae type b) – not related to influenza vaccine at all
- Hepatitis B
- HPV
- whooping cough
- pneumoccal disease
- meningococcal disease
Toxoid vaccines
Toxoid vaccines prevent diseases caused by bacteria that produce toxins in the body.
The toxins are weakened into toxoids so they cannot cause illness and are used to make the vaccine.
When the immune system receives a vaccine containing a toxoid, it learns how to fight off the natural toxin.
Example of toxoid vaccine:
- diphtheria and tetanus portions of the DTaP vaccine
Several shots are needed to build and continue immunity over time.
Passive immunization
Passive immunization is a bit different than any of the above.
Either catching a disease or getting any of the above vaccines stimulates your immune system to make memory cells to fight of that specific germ if it comes in contact with it.
Passive immunity results when a person is given someone else’s antibodies.
The protection offered by passive immunization is short-lived, usually lasting only a few weeks or months, but it helps protect right away.
Example of a passive vaccine:
- Synagis (RSV) vaccine
Why are vaccines repeatedly given?
Vaccines interact with the T and B cells of our immune system to make memory cells.
If you want to learn more, see How Vaccines Work. It’s a really cool slide show from The College of Physicians of Philadelphia.
Some vaccines need several doses to help the body develop a strong immunity against the germs. Later boosters are required to maintain that level of protection.
Other vaccines require more than one dose to insure that most people develop the protection.
Age at time of vaccine matters
The CDC Immunization schedule allows for age ranges for many vaccines to be given. Many states allow a grace period around those ages, but not all do.
Some vaccines have been shown to work best at certain ages. Our vaccine schedule reflects the best ages to give vaccines so that they are safe and effective.
If a child receives a vaccine within the grace period of their current state, it might “count.” But if that child moves to another state, the vaccine might not count per the new state’s laws.
My office only gives the routine MMR, Varicella, and Hepatitis A vaccines on or after the first birthday to help prevent a child from moving to a location that does not have a grace period. This is despite the fact that Kansas does have a 4 day grace period.
We will give the MMR earlier under certain circumstances as discussed above, but it does not count toward the two needed after the 1st birthday.
Spacing matters
Many vaccines need to be separated by a minimum timeframe, often 4 weeks, but sometimes longer. The Hepatitis A vaccine has a minimum timeframe of 6 months between doses, for example.
If the vaccine doses are not separated by a minimum time, one or more will need to be repeated.
For spacing rules, see the CDC vaccine schedule at the bottom of this post. Click on “footnotes” to see the details for each vaccine.
Why not space them out further?
Many parents have come to believe the “too many too soon” theory. They believe this despite the overwhelming evidence that vaccines are safe and effective when given according to the CDC schedule.
The risks to waiting to give vaccines are many.
Increasing vaccine preventable disease rates
Young adults of today have grown up without seeing the suffering of vaccine preventable diseases. But we’re seeing an increase in these diseases where vaccine rates have fallen.
Infants who aren’t vaccinated are at risk of diseases that can lead to death. They are among the most vulnerable and need protection.
More trips = more exposure
Not only are underimmunized children more at risk for vaccine preventable diseases, but bringing them to a clinic more frequently to do one vaccine a time increases risk. Each time they visit the clinic, they’re exposed to all the common viruses. Why risk bringing them back again and again to get more exposures?
Giving the vaccines together has been shown to be safe and effective.
More visits = more stress
There are studies that show less overall stress to the body if vaccines are given together.
Studies have shown that the first injection causes a stress response measured by elevated heart rate, blood pressure, cortisol levels, and cry. Subsequent injections given at the same time do not increase as significantly the stress when compared to returning on different days to get further injections.
The immune system can handle it
Are you worried about “too many too soon” and that vaccines will overwhelm the immune system? Stop worrying. These fears are simply unfounded.
As Paul Offit summarized in Addressing Parents’ Concerns: Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?:
Current studies do not support the hypothesis that multiple vaccines overwhelm, weaken, or “use up” the immune system. On the contrary, young infants have an enormous capacity to respond to multiple vaccines, as well as to the many other challenges present in the environment. By providing protection against a number of bacterial and viral pathogens, vaccines prevent the “weakening” of the immune system and consequent secondary bacterial infections occasionally caused by natural infection.
Keep your child’s vaccine record handy
I see many kids who transfer to my office but I don’t have access to their vaccine records at the time of the visit. This makes it difficult to know which (if any) vaccines are needed.
Hopefully as we use Electronic Health Records with portals and vaccine registry databases more this will become a non-issue. At this time it’s still a problem.
This is one of the many reasons I prefer for all vaccines to be given at the same clinic. If you’re changing primary care providers, be sure records are transferred before your first visit.
Flu vaccines are especially troublesome.
Flu vaccines are commonly given in many locations: your primary care provider (PCP) office, a parent’s workplace, a local pharmacy, at a school flu vaccine drive. They need to be repeated yearly, so it’s easy to forget if each of your kids has had it this year.
It’s common for one parent to not know if their child got a flu vaccine already this season. That leads to a missed opportunity or vaccines given unnecessarily.
I have seen a few kids who couldn’t get their kindergarten vaccines at their well visit because they recently had a FluMist elsewhere. That requires another trip to the office for the family.
I have seen a few kids who did get the kindergarten vaccines inappropriately because the parent didn’t realize the other parent had taken them for a FluMist elsewhere. They needed to repeat the MMR and varicella vaccines, which didn’t make the kids happy!
FluMist is coming back to the US for the 2018-2019 flu vaccine season. It is not the preferred vaccine by many experts due to continued concerns about its effectiveness, but it will be preferred by many kids who hate needles. If your kids worry about shots, learn how to make them less painful.
Be sure to keep track if your kids get a FluMist – especially if they’re getting kindergarten vaccines around the same time!
Learn more about vaccine preventable diseases:
This comic book can teach kids and adults about viruses and how science works:
Dr. Paul Offit is one of the leading experts on vaccines. His many books can show how vaccines work and why they’re needed. He delves into the anti-vaccine movement in many of his books. He shows how delayed vaccine schedules are not effective or necessary in most of his books. I have many of these at my office available for patient families to check out. Just ask if you’re in my office. Otherwise, read about each on the links to see what best fits your needs.
Note: As an Amazon Affiliate Member, I will get a small percentage for the sale of the books if purchased from these links. This is at no additional cost to you.
Vaccine Resources for Kids and Teens is a great list of resources from the Children’s Hospital of Philadelphia.
15 Common Anti-Vaccine Arguments and Why They are a Load of Crap
How Math (and Vaccines) Keep You Safe From the Flu Simple (or not so simple) math shows how herd immunity works. Widespread vaccination can disrupt the exponential spread of disease and prevent epidemics.
Simulation of how herd immunity works. Is a free online simulation. Try it!
The CDC schedule:
