Tag: immune response

Did Dr. Bob Uncover a CDC Plot to Give Adult Flu Shots to Babies?

Have you heard the news?

Uh, the ACIP can't request a license for a vaccine...
Uh, the ACIP can’t request a license for a vaccine…

Dr. Bob and his new podcasting side kick think that the “CDC wants the FDA to approve adult doses of the flu vaccine for babies, because the normal half-doses approved for babies don’t work well enough.”

Did Dr. Bob Uncover a CDC Plot to Give Adult Flu Shots to Babies?

This is likely going to surprise Dr. Bob, but many infants already get the same dose of flu vaccine as adults.

Both FluLaval and Fluarix are given at the same 0.5ml dose, containing 15 µg of HA per vaccine virus, to infants, older children, and adults.

Fluzone, on the other hand, is still given at a 0.25ml dose, containing 7.5 µg of HA per vaccine virus, to children between the ages of 6 months to three years, and a larger 0.5ml dose to older kids and adults.

Why the differences?

“In a randomized trial comparing immunogenicity and safety of 0.5 mL FluLaval Quadrivalent with 0.25 mL Fluzone Quadrivalent, safety and reactogenicity were similar between the two vaccines.”

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season

Because they are just as safe at the lower doses and might actually work better.

Then why did we ever use a lower dose for infants?

That recommendation was based on the older, whole-virus version of the flu shot, which did cause more side effects for infants when given at a full dose. We now use split-virus flu shots that don’t have this problem.

And now, the manufacturer of Fluzone has done a study, and not surprisingly, they have also found that “safety profile of a 0.5 ml (full-dose) is similar to 0.25 ml (half-dose) and may be more immunogenic.”

So they are submitting a BLA to the FDA for the use of the 0.5ml dose of their flu vaccine for infants.

What about the idea of an “adult dose of mercury” for infants?

Over 80% of flu vaccines were thimerosal free this year. You almost have to go out of your way to get your kids a flu vaccine with thimerosal, so no, this won’t mean an “adult dose of mercury” for your infant.

Most importantly though, if you understand how vaccines work, you know that the dose of vaccines for kids and adults is not calibrated by weight or age, so none of this really matters. The immune reaction that helps antibodies travel all through your body starts locally, near where the vaccine was given, so a 20-pound infant and a 200-pound adult can get the same dose of flu shot and both can be protected.

More on Dr. Bob’s CDC Plot to Give Adult Flu Shots to Babies

Is There a Grace Period for Getting Vaccines?

You know about the standard immunization schedule.

Looking at the latest immunization schedule from the CDC and AAP, it should be clear that kids don't get 69 vaccines.
What happens if you get a vaccine a few days too early?

You may even know about the minimum ages or minimum intervals between vaccines, but what happens if your child gets a vaccine just a few days early?

Is There a Grace Period for Getting Vaccines?

Fortunately, in most cases, getting a vaccine just a little early isn’t going to mean that the vaccine dose has to be repeated.

“Doses administered too close together or at too young an age can lead to a suboptimal immune response. However, administering a dose a few days earlier than the minimum interval or age is unlikely to have a substantially negative effect on the immune response to that dose. Known as the “grace period”, vaccine doses administered ≤4 days before the minimum interval or age are considered valid; however, local or state mandates might supersede this 4-day guideline.”

General Best Practice Guidelines for Immunization: Best Practices Guidance of the Advisory Committee on Immunization Practices (ACIP)

That’s because the Advisory Committee on Immunization Practices (ACIP) allows a 4-day grace period for most vaccines. So if your child got their vaccines 3 or 4 days before their 1st birthday, instead of on or after turning 12 months old, they would still count!

It is important to keep in mind that:

  • day 1 is the day before the day that marks the minimum age or minimum interval for a vaccine.
  • the grace period doesn’t apply to the rabies vaccine
  • if a vaccine is given 5 or more days too early, beyond the grace period, then the interval to the next dose starts from the day that invalid dose was given. For example, if the second dose of Hib is given two weeks after the first dose (instead of the minimum 4 weeks), then you don’t repeat this invalid dose in two weeks (four weeks from the first dose), but instead wait an additional four weeks from the invalid second dose
  • you can’t usually add the grace period to an accelerated schedule
  • live vaccines must be given at least 28 days apart if they are not given at the same time and the grace period can not be used to shorten this interval

Most importantly, in place since 2002, the grace period protects kids from having to repeat vaccines because of minor vaccine scheduling errors.

More on the Vaccine Grace Period

Why Do Some Vaccines Need Boosters?

Vaccines work.

They aren’t perfect though, which is why some vaccines need booster doses to help them provide long lasting protection.

Why Do Some Vaccines Need Boosters?

To be clear, just because you get more than one dose of a vaccine, that doesn’t make it a booster dose.

For example, infants get multiple doses of the DTaP, polio, Hib, hepatitis B, Prevnar, and rotavirus vaccines, but those are part of the primary series for those vaccines. They aren’t boosters.

“A “classical” prime-boost immunization schedule is, thus, to allow 4 to 6 months to elapse between priming and booster doses, hence the generic “0-1-6 month” (prime-prime-boost) schedule. Secondary antigen exposure thus results in the production of higher-affinity antibodies than primary responses.”

Plotkin’s Vaccines (Seventh Edition)

Getting the booster shot in a vaccine series is important to get full protection.
Getting the booster dose in a vaccine series is important to get full protection.

Classic booster doses are the:

But why do we need these booster doses?

While one or more doses of the primary series of the vaccine leads to the production of plasma cells and protective antibodies, the booster dose then causes a secondary immune response and the production of more long-lived plasma cells. That’s how we get higher levels of protective antibodies that will last longer.

Which Vaccines Don’t Need Boosters?

In general, live vaccines don’t need booster doses.

So why do we get a second dose of MMR?

This isn’t a classic booster dose. It protects the small percentage of people who don’t respond to the first dose.

Some folks may need a booster dose of the MMR vaccine in certain circumstances though, specifically if they are caught up in a mumps outbreak.

What to Know About Vaccine Booster Doses

Some vaccines need booster doses to help you get full protection. Don’t skip them.

More on Vaccine Booster Doses

Aren’t Vaccines Made for Adults?

Have you ever heard someone bring up the argument that vaccines are made for adults, so kids shouldn’t be getting the same dosage?

If they do, you should understand right away that they don’t really understand how vaccines work.

And that they really don’t understand immunology either, for that matter.

Are Vaccines Made for Adults?

To be fair, some vaccines are made just for adults. In fact, some, like the shingles vaccines and high-dose flu shot (has four times the amount of antigen in the regular flu shot) are only for seniors.

Other vaccines, like the rotavirus vaccine, are made just for kids.

And a few vaccines come in different forms depending on your age.

For example, younger kids get the DTaP vaccine, while older kids and adults get a Tdap vaccine. They both protect against the same three diseases (diphtheria, tetanus, and pertussis), but they contain different amounts of antigens. In this case, the Tdap vaccine actually contains 3-5 times less of the diphtheria component as the DTaP vaccine. That’s because before they lowered it, repeated dosing of the original Td vaccine every ten years led to worsening local reactions in some people.

The hepatitis B and hepatitis A vaccines are also available in different formulations for kids and adults, with adults getting twice the amount of antigens.

Most other vaccines though, come in the same form for both kids and adults, including the MMR vaccine and vaccines that protect us against HPV, chicken pox, polio, meningococcal disease, and pneumococcal disease, etc.

Are Vaccines Calibrated by Weight or Age?

Why does this question even come up?

Science event in Washington, D.C. reminding folks that Vaccines Work.
Pediatricians at the March for Science event in Washington, D.C. reminded folks that Vaccines Work. We shouldn’t forget that others also need a reminder of how they work.

It’s because some folks push the myth that infants are getting too high a dose of vaccines, since in most cases, older kids and adults get the very same dose.

They don’t though.

Does that mean that those older kids and adults are getting too low a dose then?

Nope.

You see, vaccines aren’t like antibiotics or other medications. They aren’t typically dosed based on your weight or age and don’t have to build up to a steady state in your blood stream.

That’s right, for most vaccines, it doesn’t matter if your child weighs 8 pounds or 80 pounds.

Why not?

Because the antigens in the vaccine don’t have to travel all around your child’s body in order for them to work!

Understanding the Immune Response to a Vaccine

Instead, the small amount of antigens in a vaccine simply get the vaccine response started near where the vaccine was given, whether that is in their arm or leg (shot), nose (nasal), or small intestine (oral).

“B cells are essentially activated in the lymph nodes draining the injection site.”

Claire-Anne Siegrist on Vaccine Immunology

Antigen-presenting cells (APCs) then take up the antigens and migrate towards a nearby lymph node. It is at these lymph nodes that the APCs activate other cells, including:

  • antigen-specific helper T cells
  • killer T cells
  • B cells

The activated T and B cells then go to work, with many B cells becoming plasma cells, and some T and B cells transforming into memory cells.

This illustration from the NIH and National Library of Medicine helps explain how vaccines work.
This illustration from the NIH and National Library of Medicine explains how vaccines work.

Next, within days to weeks of getting vaccinated, the plasma cells begin producing protective antibodies, which are released into our bloodstreams.

The same thing happens if you are exposed to a disease naturally, which is why it is silly to think that a vaccine could weaken or overwhelm your immune system.

The big difference about getting exposed to a disease naturally vs getting a vaccine? With the vaccine, you don’t have to actually have the the symptoms of the disease or any of its complications to get immunity. In other words, you don’t have to earn your immunity.

What to Know About Vaccine Dosage Myths

The dose of vaccines for kids and adults is not calibrated by weight or age because the immune reaction that helps antibodies travel all through your body starts locally, near where the vaccine was given.

More on Vaccine Dosage Myths