Tag: vaccine-associated measles

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

About Those Vaccine Strains in Measles Outbreaks…

A lot happens to control and contain a measles outbreak these days.

For one thing, you have to confirm that everyone with measles symptoms actually has measles. If you miss anyone, because measles is so contagious, then they could expose other people and the outbreak will keep getting bigger.

How do they confirm who has measles and who doesn’t?

While you could just make a clinical diagnosis, simply relying on the person’s history and pattern of symptoms, typically everyone just gets tested.

About Those Vaccine Strains in Measles Outbreaks…

What kind of testing?

“Laboratory confirmation is essential for all sporadic measles cases and all outbreaks. Detection of measles-specific IgM antibody and measles RNA by real-time polymerase chain reaction (RT-PCR) are the most common methods for confirming measles infection. Healthcare providers should obtain both a serum sample and a throat swab (or nasopharyngeal swab) from patients suspected to have measles at first contact with them. Urine samples may also contain virus, and when feasible to do so, collecting both respiratory and urine samples can increase the likelihood of detecting measles virus.”

Measles For Healthcare Professionals

It depends, but often a throat swab or a throat swab and urine are collected for PCR testing, especially if it has been 7 or fewer days since the patient came down with their rash.

If it has been longer than 7 days, then testing using urine and blood specimens can be performed.

“Molecular analysis can also be conducted to determine the genotype of the measles virus. Genotyping is used to map the transmission pathways of measles viruses. The genetic data can help to link or unlink cases and can suggest a source for imported cases. Genotyping is the only way to distinguish between wild-type measles virus infection and a rash caused by a recent measles vaccination.”

Measles For Healthcare Professionals

Because many people get vaccinated during an outbreak and a rash and fever is a side effect of the MMR vaccine, testing becomes very important in those who were recently vaccinated.

Statistics from the 2015 Disneyland measles outbreak...
Statistics from the 2015 Disneyland measles outbreak. Anti-vaccine folks, this slide doesn’t mean what you think it means.

After getting vaccinated, testing helps confirm that someone has vaccine strain measles and not wild type, a vaccine reaction, and don’t actually have measles.

“Here, we describe a real-time reverse transcription-PCR (RT-PCR) method that detects the vaccine genotype (MeVA RT-quantitative PCR [RT-qPCR]) and that can provide rapid discrimination between wild-type-virus infections and vaccine reactions.”

Roy et al on Rapid Identification of Measles Virus Vaccine Genotype by Real-Time PCR

An no, the vaccine reaction is not that they developed measles! They developed a rash and/or fever, a common side effect of the MMR vaccine.

“During outbreaks, measles vaccine is administered to help control the outbreak, and in these situations, vaccine reactions may be mistakenly classified as measles cases.”

CDC on Genetic Analysis of Measles Viruses

So the reports that you might have seen that 31 people in the California measles outbreak had a vaccine strain of measles aren’t true. There were at least 31 people who were recently vaccinated during the outbreak and had a rash and/or fever, and they tested positive for the vaccine strain, proving that they weren’t actually part of the outbreak. None of them actually had measles though.

Has anyone ever gotten the measles after being vaccinated?

“Vaccine‐associated measles is a possible, but extremely rare event.”

Sood et al on Vaccine‐associated measles in an immunocompetent child

Yes, there are a few case reports.

Very rare case reports.

Who's to blame for low immunization rates and continuing outbreaks?
Who’s to blame for low immunization rates and continuing outbreaks?

We know who’s responsible for the rise in measles outbreaks and no, it ain’t folks who have recently been vaccinated. Vaccines are safe and necessary.

Get vaccinated. Stop the outbreaks.

More on Vaccine Strains in Measles Outbreaks

Is a Vaccine Strain Causing The Latest Measles Outbreak?

What’s the first question anti-vaccine folks start asking whenever we see a large outbreak of measles?

No, it’s not how can I get my kids vaccinated and protected so that they don’t get measles…

It is whether or not it a vaccine strain of measles started the outbreak.

That’s not how any of this works…

Where do folks get all of this stuff about genotypes and vaccine strains? I wonder…

Dr. Bob had no facts, but still posted that a vaccine strain of measles could have killed a woman who got caught up in the last measles outbreak in Washington.

Yup.

The usual suspects.

Is a Vaccine Strain Causing The Latest Measles Outbreak?

Why do folks who intentionally don’t vaccinate their kids desperately want these measles outbreaks to be caused by a vaccine strain?

Because then it isn’t their fault that their kids are at risk of getting a life-threatening disease!

It’s never a vaccine strain though.

Remember the Disneyland measles outbreak. A lot of folks were talking about vaccine strains when it first started.

“…California patients were genotyped; all were measles genotype B3, which has caused a large outbreak recently in the Philippines…”

Measles Outbreak — California, Dec 2014–Feb 2015

It wasn’t a vaccine strain.

OutbreaksYearGenotype
Minnesota2017B3
Tennessee2016B3
California2015B3
Florida2013D8
California2014B3, D8
Brooklyn2013D8
North Carolina2013D8
Minnesota2011B3
Washington, Illinois2008D5, D4

For example, during 2011, 222 cases of measles and 17 outbreaks were reported in the United States, with most cases originating from just five countries (France, Italy, Romania, Spain, and Germany). Six different genotypes were identified, including B3, D4, G3, D8, H1, and D9. No vaccine strains…

And no, it doesn’t matter that the vaccine strain of measles, genotype A, differs from all of the wild strains of measles we see in the outbreaks.

“Vaccine induced immunity protects against all virus strains. Measles is considered a monotypic virus despite the genetic variations.”

Factsheet about measles

Unlike the flu, HPV, and pneumococcal bacteria, in which vaccines only protect against different serotypes, in the case of measles, the genotype simply helps us figure out where the measles case came from.

And no, the latest outbreak, wherever it is, wasn’t caused by shedding from a vaccine.

But if it isn’t the vaccine strain, then why do they that is it important to rapidly identify wild strains vs vaccine strains?

“During measles outbreaks, it is important to be able to rapidly distinguish between measles cases and vaccine reactions to avoid unnecessary outbreak response measures such as case isolation and contact investigations.”

Roy et al on Rapid Identification of Measles Virus Vaccine Genotype by Real-Time PCR

That’s easy to answer.

Outbreaks typically trigger a lot of folks to get vaccinated. While that’s great, one possible problem is that some of those folks might develop a fever and/or rash after their MMR vaccine. So it is important to quickly figure out whether they are part of the outbreak and have a wild strain (maybe they were exposed before their vaccine could start to work) or are having a common, mild vaccine reaction.

But couldn’t they have vaccine-associated measles if they have a rash and fever and a vaccine strain? Theoretically, but then they would likely have true measles symptoms. And even in these rare case reports, the children didn’t spread the measles to anyone else.

So why are you waiting to know the genotype of the measles strain causing the outbreak in your area? Hopefully, it isn’t to help you decide whether or not to vaccinate and protect your kids. While it is interesting to know where the outbreak originated, you can bet that it isn’t a vaccine strain.

More on Vaccine Strains Causing Measles Outbreaks