Tag: math

What’s Your Chance of Getting Measles Right Now?

It shouldn’t be a surprise that a lot of folks are thinking about their risk of getting measles right now.

But with record levels of measles cases this year, some of us are thinking about our level of risk much differently than others.

rIf you are unvaccinated and exposed to someone with measles, you risk is actually 1,000,000 times higher…

While most of us simply want to make sure we are vaccinated and protected, anti-vaccine folks are taking every opportunity to downplay their risks.

What’s Your Chance of Getting Measles Right Now?

So what’s your chance of getting measles?

“Measles is one of the world’s most contagious diseases. It is spread by coughing and sneezing, close personal contact or direct contact with infected nasal or throat secretions. The virus remains active and contagious in the air or on infected surfaces for up to 2 hours. It can be transmitted by an infected person from 4 days prior to the onset of the rash to 4 days after the rash erupts.”

WHO on Measles

That’s actually not that simple to figure out, but depends on:

Those who have had two doses, with no plans to travel, and who live in an area with no reported cases, are at extremely low risk to get measles – the risk won’t be zero until measles is eradicated.

In this kind of low risk situation, kids don’t need early doses of MMR vaccines and most adults can probably get away with just having one dose of MMR.

“Measles is highly contagious and spreads through the air when an infected person coughs or sneezes. It is so contagious that if one person has it, 9 out of 10 people of all ages around him or her will also become infected if they are not protected.”

CDC on Measles is Highly Contagious

On the other hand, if you are unvaccinated and were at the AMC Theater on Lemon Street in Fullerton, between 11 p.m. and 4 a.m. on April 25, then your chance of getting measles is about 90%!

Wait! That’s a little more than the 0.000092% chance that anti-vaccine folks are throwing around…

The odds of being hit by lightning are low because we practice storm safety and don’t run around outside when we see lightning!

To think of it another way, if you knew that your chances of getting hit by lightning were a little over 1 in a million, would that make you think it is okay to go outside and play golf during a severe thunderstorm?

Would you think the risk is so low that you could let your kids play outside if you heard thunder and saw lightning flashes nearby, or would you all rush inside?

That’s right! The risk of getting hit by lightning is low because most of us don’t take chances when we hear thunder or see lightning.

It’s the same with measles and other vaccine-preventable diseases.

The overall risk is low because most people are vaccinated and protected!

If you aren’t vaccinated and protected, as we see more and more cases, your risk of getting sick, and getting others sick, is going to continue to get higher and will always be much higher than someone who is fully vaccinated, no matter how much you want to believe in shedding, mild measles, or whatever myths help you justify keeping your kids unvaccinated and unprotected during an outbreak.

Remember, you can’t hide in the herd if you are scaring away too much the herd

Vaccines are safe, with few risks, and are obviously necessary.

You can avoid getting measles.
You can greatly reduce your family’s risk of getting measles.

Make sure your family is protected so they don’t get caught up in a measles outbreak

More on Your Chance of Getting Measles


Do More Vaccinated or Unvaccinated Kids Get Pertussis?

While this seems like a simple question, the answer is a bit more complicated than most people imagine.

Do More Vaccinated or Unvaccinated Kids Get Pertussis?

For anti-vaccine folks, the answer is clear – more vaccinated kids get pertussis. They put all of the blame for pertussis outbreaks on waning immunity. Of course, that’s not the whole story.

While 10% of kids got pertussis, unless you are at a Waldorf school, it is unusual to find that many completely unvaccinated children.
While 10% of kids got pertussis, unless you are at a Waldorf school, it is unusual to find that many completely unvaccinated children. Plus, we don’t know the vaccine history of 40% of these kids.

While it might technically be true that more vaccinated kids get pertussis in the average outbreak, that’s only because there are many more vaccinated kids!

A more accurate and useful answer, taking into account attack rates, makes it clear that a higher percentage of unvaccinated kids get pertussis in these outbreaks.

“In conclusion we have described a school-based outbreak of pertussis that may have been fueled by moderate vaccine effectiveness combined with a failure to vaccinate.”

Terrenella et al on Vaccine effectiveness of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine during a pertussis outbreak in Maine

In a pertussis outbreak in Maine, attack rates were much higher in unvaccinated kids, even though more vaccinated kids got pertussis. While 29 of 214 vaccinated kids got pertussis, a much higher percentage of unvaccinated kids got sick – 6 of 28.

That means your risk of getting pertussis was much higher if you were unvaccinated.

A 2013 pertussis outbreak in Florida is a good example that even with all the bad press it gets, the DTaP and Tdap vaccines work too. This outbreak was started by an unvaccinated child at a charter school with high rates of unvaccinated kids. About 30% of unvaccinated kids got sick, while there was only one case “in a person who reported having received any vaccination against pertussis.”

In another 2013 pertussis outbreak in Florida, this time in a preschool, although most of the kids were vaccinated, the outbreak started with “a 1-year-old vaccine-exempt preschool student.” And the classroom with the highest attack rate, was “one in which a teacher with a laboratory-confirmed case of pertussis who had not received a Tdap booster vaccination, worked throughout her illness.”

Why do so many unvaccinated kids get pertussis these days?

“We found evidence of an increase in exemption rates, spatial clustering of nonmedical exemptions, and space-time clustering of pertussis in Michigan. There was considerable overlap between the clusters of exemptions and the clusters of pertussis cases.”

Omer et al on Geographic Clustering of Nonmedical Exemptions to School Immunization Requirements and Associations With Geographic Clustering of Pertussis

Besides the fact that they are unvaccinated and unprotected?

“Children of parents who refuse pertussis immunizations are at high risk for pertussis infection relative to vaccinated children. Herd immunity does not seem to completely protect unvaccinated children from pertussis.”

Glanz et al on Parental refusal of pertussis vaccination is associated with an increased risk of pertussis infection in children.

They can’t get away with hiding in the herd.

Another important consideration – in addition to the fact that more unvaccinated kids get pertussis, when they get pertussis, it is more severe than those who are vaccinated.

“Serious pertussis symptoms and complications are less common among age-appropriate number of pertussis vaccines (AAV) pertussis patients, demonstrating that the positive impact of pertussis vaccination extends beyond decreasing risk of disease.”

McNamara et al on Reduced Severity of Pertussis in Persons With Age-Appropriate Pertussis Vaccination-United States, 2010-2012.

Still thinking of skipping or delaying your child’s pertussis vaccine?

More on Do More Vaccinated or Unvaccinated Kids Get Pertussis?

Do Kids Really Get 72 Doses of Vaccines?

Most parents vaccinate their kids according to the recommended immunization schedule.

They know that’s the best way to keep them protected.

Do Kids Really Get 72 Doses of Vaccines?

Saying kids get 72 doses of vaccines is a propaganda too to scare parents.
Saying kids get 72 doses of vaccines is a propaganda tool to scare parents.

While kids do get more vaccines than their parents did, that’s only because we have more vaccines available to protect them from more now vaccine-preventable diseases.

Do they get their kids 72 doses of vaccines?

That sounds like a lot…

It sounds like a lot because it is an inflated number that is meant to scare parents.

Kids today do routinely get:

  • 13 vaccines, including 5 doses of DTaP, 4 doses of IPV (polio), 3 or 4 doses of hepatitis B, 3 or 4 doses of Hib (the number of doses depends on the vaccine brand used), 4 doses of Prevnar, 2 or 3 doses of rotavirus (the number of doses depends on the vaccine brand used), 2 doses of MMR, 2 doses of Varivax (chicken pox), 2 doses of hepatitis A, 1 doses of Tdap, 2 or 3 doses of HPV (the number of doses depends on the age you start the vaccine series), 2 doses of MCV4 (meningococcal vaccine), and yearly influenza vaccines
  • protection against 16 vaccine-preventable diseases, including diphtheria, tetanus, pertussis, measles, mumps, rubella, polio, chicken pox, pneumococcal disease, hepatitis A, hepatitis B, meningococcal disease, HPV, rotavirus, Hib, and flu
  • about 28 doses of those vaccines by age two years (with yearly flu shots)
  • about 35 doses of those vaccines by age five years (with yearly flu shots)
  • as few as 23 individual shots by age five years if your child is getting combination vaccines, like Pediarix or Pentacel and Kinrix or Quadracel and Proquad
  • about 54 doses of those vaccines by age 18 years, with a third of that coming from yearly flu vaccines

How do you get a number like 72?

You can boost your count to make it look scarier by counting the DTaP, MMR, and Tdap vaccines as three separate vaccines each, even though they aren’t available as individual vaccines anymore.

To boost the Vaccine Doses for Children a bit more, they add pregnancy doses too.
To boost the Vaccine Doses for Children a bit more, they add pregnancy doses too.

This trick of anti-vaccine math quickly turns these 8 shots into “24 doses.”

It’s not a coincidence.

Anti-vaccine folks want to scare you into thinking that vaccines are full of toxins, that kids get too many vaccines, that we give many more vaccines than other countries, and that this is causing our kids to get sick.

Can an unvaccinated child really get tetanus after a toe nail injury?
Can an unvaccinated child really get tetanus after a toe nail injury? Photo by Petrus Rudolf de Jong (CC BY 3.0)

None of it is true.

At age four years, when your preschooler routinely gets their DTaP, IPV, MMR, and chicken pox shots before starting kindergarten, how many vaccines or doses do you think they got? Two, because they got Kinrix or Quadracel (DTaP/IPV combo) and Proquad (MMR/chickenpox combo)? Four, because they got separate shots? Or Eight, because you think you should count each component of each vaccine separately?

Know that even if you do want to count them separately, it really just means that with those two or four shots, your child got protection against eight different vaccine-preventable diseases – diphtheria, tetanus, pertussis, polio, measles, mumps, rubella, and chicken pox.

Vaccine-preventable diseases that have not disappeared, something that the “72 doses” sites don’t ever warn you about.

What to Know About Anti-Vaccine Math

Many websites use anti-vaccine math to inflate vaccine dose numbers and scare parents away from vaccinating and protecting their kids.

More on Anti-Vaccine Math

Do More Vaccinated or Unvaccinated Kids Get Sick in Outbreaks?

Some anti-vaccine folks continue to claim that vaccines don’t work and that most outbreaks of vaccine-preventable diseases are actually caused by kids who have been vaccinated.

They also push the myth that more vaccinated than unvaccinated kids get sick in most outbreaks.

Vaccinated vs Unvaccinated in an Outbreak

So are outbreaks usually caused by kids who have been vaccinated?

No, of course not.

Do we sometimes see more vaccinated than unvaccinated kids in some of these outbreaks?

Yes, sometimes we do.

Vaccine Epidemiology

Wait, what?

Yes, we sometimes see more vaccinated than unvaccinated kids in an outbreak.

How can that be if vaccines work?

It is actually very easy to understand once you learn a little math and a little more epidemiology.

Basically, it is because while vaccines work, they don’t work 100% of the time, and more importantly, there are way more vaccinated kids around than unvaccinated kids.

The Mathematics of Disease Outbreaks

That means that you need to understand that more than the absolute number of vaccinated and unvaccinated people that got sick in an outbreak, you really want to know the percentages of vaccinated vs unvaccinated kids who got sick.

For example, in a school with 1,000 kids, you might be very surprised if six kids got a vaccine preventable disease, and three of them were vaccinated, leaving three unvaccinated.

Does that really mean that equal amounts of vaccinated and unvaccinated kids got sick?

I guess technically, but in the practical sense, it only would if half of the kids in the school were unvaccinated. Now unless they go to a Waldorf school, it is much more likely that over 90 to 95% of the kids were vaccinated, in which case, a much higher percentage of unvaccinated kids got sick.

Before we use a real world example, some terms to understand include:

  • attack rate – how many people will get sick when exposed to a disease
  • basic reproductive number or Ro – different for each disease, Ro basically tells you  just how contagious a disease is and ranges from about 1.5 for flu, 8 for chicken pox, and 15 for measles
  • vaccine coverage – how many people are vaccinated
  • vaccine efficacy – how well a vaccine works

You also need to know some formulas:

  • attack rate = new cases/total in group
  • vaccine coverage rate = number of people who are fully vaccinated / number of people who are eligible to be vaccinated
  • vaccine effectiveness = (attack rate in unvaccinated group – attack rate in vaccinated group) / attack rate in unvaccinated group x 100

Unfortunately, it is often hard to use these formulas in most outbreaks.

Why?

For one thing, it is hard to get accurate information on the vaccination status of all of the people in the outbreak. In addition to those who are confirmed to be vaccinated or unvaccinated, there is often a large number who’s vaccination status is unknown. And even if you know the vaccination status of everyone in the outbreak, it can be even harder to get the vaccine coverage rate or a neighborhood or city.

Outbreaks of Vaccine Preventable Diseases

Reports of measles outbreaks among highly vaccinated populations are from before we started doing a second dose in 1994.
Reports of measles outbreaks among highly vaccinated populations are from before we started doing a second dose of MMR… way back in 1994.

We know what starts most outbreaks.

And no, it’s not shedding

For example, with measles, it is typically an unvaccinated person who travels out of the country, returns home after they have been exposed but are still in their incubation period, and then exposes others once they get sick. And the great majority of folks in these measles outbreaks are unvaccinated.

Some examples of these outbreaks include:

  • the 2014 Ohio measles outbreak that started with two unvaccinated Amish men getting measles in the Philippines while on a missionary trip and ended up with at least 388 cases before it was over, almost all unvaccinated
  • a 2013 North Carolina measles outbreak with 22 cases started after an unvaccinated traveler had returned from India
  • an outbreak of measles in New York, in 2013, with at least 58 cases, tarted with an intentionally unvaccinated teen returning from a trip to London
  • a 2011 outbreak of measles in Minnesota, when an unvaccinated child traveled out of the country, developed measles, and returned to his undervaccinated community, causing the state’s largest measles outbreak in 20 years

But what about mumps and pertussis?

Those outbreaks are all among vaccinated kids, right?

Nope.

In one of the biggest mumps outbreak, in Arkansas, only 71% of people were up-to-date on their vaccines!

And keep in mind that while we do know that there are issues with waning immunity with some vaccines, you are still much more likely to become infected and get others sick if you are not vaccinated. And you will likely have a much more severe disease.

A 2013 pertussis outbreak in Florida is a good example that even with all the bad press it gets, the DTaP and Tdap vaccines work too. This outbreak was started by an unvaccinated child at a charter school with high rates of unvaccinated kids. About 30% of unvaccinated kids got sick, while there was only one case “in a person who reported having received any vaccination against pertussis.”

In another 2013 pertussis outbreak in Florida, this time in a preschool, although most of the kids were vaccinated, the outbreak started with “a 1-year-old vaccine-exempt preschool student.” And the classroom with the highest attack rate, was “one in which a teacher with a laboratory-confirmed case of pertussis who had not received a Tdap booster vaccination, worked throughout her illness.”

In outbreak after outbreak, we see the same thing, sometimes with deadly consequences – an unvaccinated child or adult triggers an outbreak and then a lot of unvaccinated folks get sick. Unfortunately, others get caught up in these outbreaks too, including those too young to be vaccinated, those who can’t be vaccinated because of true medical exemptions, and those whose vaccines may not have worked as well as we would have liked.

Get educated.

Vaccines are safe. Vaccines are necessary. Vaccines work.

What to Know About Vaccinated vs Unvaccinated in Outbreaks

Most outbreaks are started by someone who is unvaccinated, often after a trip out of the country, and the resulting outbreak will likely get many more unvaccinated than vaccinated folks sick.

More About Vaccinated vs Unvaccinated in Outbreaks