How Much Shedding Would a Vaccine Shed…

Are you still confused about vaccine shedding?

You should be worried about wild diseases, not shedding from vaccines.
You should be worried about wild diseases, not shedding from vaccines.

As this infographic describes, it really isn’t that complicated…

What Does Vaccine Shedding Really Mean?

To clear up some things:

  • yes, some vaccines do actually shed, but it is rarely a reason to avoid getting vaccinated and protected
  • of the vaccines that we use routinely, shedding is limited to the rotavirus vaccines, FluMist, and the chickenpox vaccines
  • some other vaccines that can shed include the oral polio vaccine and the smallpox vaccine
  • the rubella component of MMR may very rarely shed, but only in breastmilk

If vaccines do shed, why shouldn’t we be more concerned about it?

Well, for one thing, most vaccines don’t shed.

DTaP, hepatitis A, hepatitis B, Hib, flu, IPV, HPV, meningococcal, pneumococcal, and Tdap shots – none of them shed.

And then there is the fact that:

  • when a vaccine sheds, it is the weakened or attenuated vaccine strain, not the wild strain that would cause more serious disease. Putting it another way, if the vaccine strain doesn’t make the person who is getting immunized sick, then why would it get someone else sick if they got it through shedding? Of course, there is a situation in which even a vaccine strain could be dangerous, and that’s for those who are severely immunosuppressed. Still, natural disease would be bad for these kids too!
  • even with oral polio vaccines, the problem isn’t really shedding, which actually provides a type of passive immunization in areas where polio is still not well controlled. The problem is that very rarely, the attenuated virus in the oral polio vaccine can revert to a form that can cause the person who was vaccinated to actually develop polio (VAPP). Now, shedding of this strain would be a problem, but only if the other person wasn’t immune.
  • rotavirus vaccines only shed in stool. You can avoid it by washing your hands when you change your child’s diapers, which you hopefully do anyway.
  • FluMist is attenuated and cold-adapted, which means that it won’t replicate well in our warmer nasal passages and respiratory tracts.
  • you have to actually get a rash, which is rare, for the chickenpox vaccine to shed.
  • it is only kids with eczema that usually get sick if they are exposed to someone who recently had the smallpox vaccine. Since the smallpox vaccine causes skin reactions, even the attenuated vaccine strain can cause severe reactions if a child’s skin is already broken down, like with eczema.

Are you still concerned about shedding?

Can a Vaccinated Person Transmit Measles Through Shedding?

To put your mind at ease, understand that you are not going to get measles from shedding.

“In this systematic review, we have determined that there have been no confirmed cases of human-to-human transmission of the measles vaccine virus.”

Greenwood et al on A systematic review of human-to-human transmission of measles vaccine virus

Well, at least not from someone who was recently vaccinated shedding a vaccine-strain of measles

If you aren’t vaccinated and protected, you could easily get it from someone who has measles and who is shedding the wild type virus though. Measles is so contagious, you just have to be in the same room as someone with measles and you will likely get sick. In fact, you can enter a room a few hours after they have left and sill catch measles!

And in theory, if someone developed vaccine-associated measles – they got sick with a vaccine-strain of measles after getting vaccinated – then they could spread the virus to someone who wasn’t immune. That’s just because they would be contagious though, not anything specific to vaccines and shedding. Also, it is basically unheard of for this to happen.

Dectecting vaccine strain measles in urine isn't something to be concerned about because it can't lead to an infection. Measles is spread through respiratory secretions, not urine.
Dectecting vaccine strain measles in urine isn’t something to be concerned about because it can’t lead to an infection. Measles is spread through respiratory secretions, not urine.

What about all of those folks who test positive for vaccine-strain measles during an outbreak?

That’s not about shedding either.

They aren’t even people with measles. Instead, they typically have a vaccine reaction, a rash and/or fever after getting their MMR and they test positive for the vaccine strain of measles because they just got a live virus vaccine.

Is Vaccine Shedding a Threat?

Shedding isn’t the threat that anti-vaccine folks make it out to me.

Think about it. If it really was a big problem, then why don’t more intentionally unvaccinated kids with exemptions get sick when they are around kids who are vaccinated?

“Health officials should require a two-week quarantine of all children and adults who receive vaccinations. This is the minimum amount of time required to prevent transmission of infectious diseases to the rest of the population, including individuals who have been previously vaccinated.”

Sally Fallon Morell, president of the Weston A. Price Foundation

We don’t actually quarantine anyone after they are vaccinated, so why don’t more kids with immune system problems get sick via shedding?

Or just think about what happens in a typical daycare or school. All of the kids don’t get vaccinated on the same day, so if shedding was an issue, wouldn’t the kids who had gotten their vaccines first shed on the ones who weren’t yet vaccinated, getting them sick?

Of course, this doesn’t happen. Again, shedding isn’t the threat that anti-vaccine folks make it out to be.

More on Vaccine Shedding

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