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

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