Tag: measles outbreaks

What to Do If Your Child Is Exposed to Measles

Although the endemic spread of measles was eliminated way back in 2000, we still have measles outbreaks in the United States.

How does that work?

They are usually imported from outside the country, often by an unvaccinated child or adult who travels overseas, gets measles, and returns while still contagious.

How Contagious is Measles?

Measles is highly contagious.

“Measles is so contagious that if one person has it, 90% of the people close to that person who are not immune will also become infected.”

CDC on Transmission of Measles

In addition to the fact that people with measles are contagious for at least four days before they develop the classic measles rash until four days after, the measles virus can survive for up to two hours in the air and on contaminated surfaces wherever that person cough or sneezed. So you don’t technically need to even be in direct contact with the person with measles – simply entering a room or getting on a bus that the infected person recently left can do it.

An infant hospitalized during a measles outbreak in the Philippines in which 110 people died.
An infant hospitalized during a measles outbreak in the Philippines in which 110 people died. Photo by Jim Goodson, M.P.H.

Still, you are not going to get measles from simply being in the same city as someone else with measles.

The tricky part though, is knowing what to do if your child is exposed to someone with measles, even if you think they are up-to-date with their vaccines.

Remember, kids get their first dose of MMR when they are 12 to 15 months old. While the second dose of MMR isn’t typically given until just before kids start kindergarten, when they are 4 to 6 years old, it can be given earlier. In fact, it can be given anytime after your child’s first birthday, as long as 28 days have passed since their first dose.

“Evidence of adequate vaccination for school-aged children, college students, and students in other postsecondary educational institutions who are at risk for exposure and infection during measles and mumps outbreaks consists of 2 doses of measles- or mumps-containing vaccine separated by at least 28 days, respectively. If the outbreak affects preschool-aged children or adults with community-wide transmission, a second dose should be considered for children aged 1 through 4 years or adults who have received 1 dose. In addition, during measles outbreaks involving infants aged <12 months with ongoing risk for exposure, infants aged ≥6 months can be vaccinated.”

CDC on Prevention of Measles, Rubella, Congenital Rubella Syndrome, and Mumps, 2013: Summary Recommendations of the Advisory Committee on Immunization Practices

And although it won’t count as their first dose, in special situations, kids can get an early MMR once they are six months old.

What to Do If Your Unvaccinated Child Is Exposed to Measles

To be considered fully vaccinated and protected against measles, kids need two doses of MMR – one at 12 to 15 months and another when they are 4 to 6 years.

“During measles, rubella, or mumps outbreaks, efforts should be made to ensure that all persons at risk for exposure and infection are vaccinated or have other acceptable evidence of immunity.”

CDC on Prevention of Measles, Rubella, Congenital Rubella Syndrome, and Mumps, 2013: Summary Recommendations of the Advisory Committee on Immunization Practices

If your unvaccinated child is exposed to measles, you should talk to your pediatrician or local health department about starting post-exposure prophylaxis as soon as possible, including:

  • a dose of immune globulin (IGIM) if they are less than 6 months old
  • either a dose of immune globulin (IGIM) or the MMR vaccine if they are between 6 and 12 months old (this dose of MMR doesn’t count as the first dose of MMR on the immunization schedule and will need to be repeated when the child turns 12 months old)
  • a dose of the MMR vaccine if they are at least 12 months old
  • a dose of immune globulin (IGIV) if they are severely immunocompromised (even if they were previously vaccinated)

Immune globulin should be given within 6 days of exposure, while a dose of MMR vaccine within 72 hours of exposure can decrease their chances of getting measles.

“Persons who continue to be exempted from or who refuse measles vaccination should be excluded from the school, child care, or other institutions until 21 days after rash onset in the last case of measles.”

Manual for the Surveillance of Vaccine-Preventable Diseases

Be sure to alert your pediatrician if you think your child might have measles or another vaccine-preventable disease.
Be sure to alert your pediatrician if you think your child might have measles or another vaccine-preventable disease.

What if your child is incompletely vaccinated, with just one dose of MMR? They could get their second dose of MMR, as long as they are over 12 months old and it has been at least 28 days since their first dose (see below).

Unvaccinated kids who don’t get post-exposure prophylaxis should be quarantined, as you watch for signs and symptoms of measles developing over the next 21 days. Your child might still need to be quarantined if they got immune globulin instead of the vaccine, and the quarantine might extend to 28 days, as immune globulin can prolong the incubation period.

If your exposed child develops measles, be sure to call your health care provider before going in for a visit, so that they can be prepared to see you and so you don’t expose other people to measles. Your child with suspected measles should be wearing a mask before going out in public and if possible, will be put in a negative pressure room in the emergency room or doctor’s office. If a regular exam room is used, it can not be used again for at least two hours. It is very important to understand that simply wearing a mask doesn’t eliminate the risk that your child with measles could expose others, it just reduces the risk. You still want to avoid other people!

What to Do If Your Vaccinated Child Is Exposed to Measles

If your fully vaccinated child is exposed to measles, does that mean you are in the clear?

Again, it depends on what you mean by fully vaccinated.

Is your child fully vaccinated for his age or has he had two doses of MMR?

Since kids get their first dose of MMR at 12 to 15 months and the second when they are 4 to 6 years old, it is easy to see that many infants, toddlers and preschoolers who are following the immunization schedule are not going to be fully vaccinated against measles, even if they are not skipping or delaying any vaccines.

“In the case of a local outbreak, you also might consider vaccinating children age 12 months and older at the minimum age (12 months, instead of 12 through 15 months) and giving the second dose 4 weeks later (at the minimum interval) instead of waiting until age 4 through 6 years.”

Ask the Experts about MMR

In some cases, documentation of age-appropriate vaccination with at least one dose of MMR is good enough protection, which means that toddlers and preschoolers don’t necessarily need an early second dose. That’s because the focus in controlling an outbreak is often on those folks who don’t have any evidence of immunity – the unvaccinated.

And one dose of MMR is about 95% effective at preventing measles infections. A second dose does increase the vaccine’s effectiveness against measles to over 99%, but it isn’t a booster. The second dose of MMR is for those kids that didn’t respond to the first dose.

“Available data suggest that measles vaccine, if given within 72 hours of measles exposure to susceptible individuals, will provide protection or disease modification in some cases. Measles vaccine should be considered in all exposed individuals who are vaccine-eligible and who have not been vaccinated or have received only 1 dose of vaccine.”

AAP RedBook

An early second dose is a good idea though if your child is exposed to measles, has only had one dose of MMR, and is age-eligible for the second dose (over age 12 months and at least 28 days since the first dose). Your child would eventually get this second dose anyway. Unlike the early dose before 12 months, this early dose will count as the second dose of MMR on the immunization schedule.

You should still watch for signs and symptoms of measles over the next 10 to 21 days though, as no vaccine is 100% effective. Your vaccinated child won’t need to be quarantined though.

Most importantly, in addition to understanding that vaccines are safe and necessary, know that the ultimate guidance and rules for what happens when a child is exposed to measles will depend on your local or state health department.

What to Know About Getting Exposed to Measles

Talk to your pediatrician if your child gets exposed to measles to make sure he doesn’t need post-exposure prophylaxis to keep him from getting sick, even if you think he is up-to-date on his vaccines.

More on Getting Exposed to Measles

Recommendations for Reporting on Measles Outbreaks

Unfortunately, we hear news reports about measles outbreaks a lot more than we should.

We don’t get much information in many of those news reports though…

Anatomy of a Measles Outbreak Report

The big reason we don’t get a lot of information in those news reports is that many of them are simply repeating health department press releases.

A news release from the Texas Department of State Health Services.
A news release from the Texas Department of State Health Services.

Those press releases often leave a lot of important information out though.

Although that information might not be available yet, if you are a journalist covering a measles outbreak, instead of simply repeating the health department news release, you might call the local or state health department and ask a few questions:

  • Where did the person get measles? Most cases these days are imported – an unvaccinated person travels out of the country and returns home with measles, starting an outbreak. If they didn’t recently travel out of the country, then there’s a problem – where did they get measles? Unless there is already an ongoing outbreak in the area, then that means someone else in the area has measles that we don’t know about.
  • Where did the person go while they were still contagious and might have exposed others?
  • Hold old are they and were they vaccinated?

Do we have a right to this information? While the Health Insurance Portability and Accountability Act (HIPAA) protects a person’s medical information, those rules don’t necessarily always apply in an emergency or outbreak situation. Plus, you are still getting de-identified information.

“Health care providers may share patient information with anyone as necessary to prevent or lessen a serious and imminent threat to the health and safety of a person or the public.”

HHS on HIPAA Privacy in Emergency Situations

How is knowing someone’s vaccination status going to be helpful? Unvaccinated folks tend to cluster together, so knowing the person is unvaccinated, especially an unvaccinated child, might indicate that many more people have been exposed. But then, most measles outbreaks are started by someone who is unvaccinated

Important Points for Covering Measles Outbreaks

An infant hospitalized during a measles outbreak in the Philippines in which 110 people died.
The symptoms of measles include a high fever, cough, runny nose, and red, watery eyes. The rash doesn’t start until 3-5 days later, as the fever continues. Photo by Jim Goodson, M.P.H.

In addition of covering the basics about the person with measles, there are other important points to cover, especially that measles is a vaccine-preventable disease!

Two doses of the MMR vaccine offers great protection against measles, and is especially important if you are unvaccinated and are going to travel out of the country. Even infants as young as six months old should get an MMR before international travel.

While most people hopefully know all that, they may not know:

  • the vaccination rates in your area schools
  • the non-medical vaccine exemption rates in your area schools
  • the number of measles cases in your area and in your state over the past few years
  • that measles is very costly to contain
  • that the incubation period for measles is 10 to 21 days after you were exposed, so it can take that long before you show symptoms
  • that they should warn their doctor or hospital before getting evaluated so that they can make sure you don’t expose other people, as measles is very, very contagious
  • that the quarantine period for unvaccinated people who have been exposed to someone with measles is typically up to 21 days after their last possible contact
  • that a dose of MMR within three days of exposure can help prevent your child from getting measles if they aren’t already fully vaccinated
Vaccine preventable diseases are just a plane ride away.
Vaccine preventable diseases are just a plane ride away.

You should also consider interviewing and quoting a local pediatrician and reinforcing the facts that vaccines work and they are safe.

And obviously, as we see with these outbreaks, vaccines are necessary.

You should avoid also false balance in your reporting.

You should fully cover each outbreak in your area, as they help remind people to get vaccinated and protected.

What to Know About Reporting on Measles Outbreaks

Journalists can help reduce the size of measles outbreaks with good reporting that vaccines work and that they are safe and necessary and by reminding folks to get vaccinated and protected.

More on Recommendations for Reporting on Measles Outbreaks

Measles Propaganda from The Physicians for Informed Consent

Most people understand that measles can be deadly.

“Measles is a highly contagious, serious disease caused by a virus. Before the introduction of measles vaccine in 1963 and widespread vaccination, major epidemics occurred approximately every 2–3 years and measles caused an estimated 2.6 million deaths each year.”

WHO Measles Fact Sheet

In the United States alone, in the pre-vaccine era, “an average of 549,000 measles cases and 495 measles deaths were reported annually.”

That roughly translates into about one death for every 1,000 cases, or a case-fatality rate of about 0.1%.

That’s in line with the typical case-fatality rate of measles of 0.1 to 0.2%.

Just How Deadly Is Measles?

Not surprisingly, many others have reported a similar case-fatality rate for measles.

Not everyone though.

The ironically named Physicians for Informed Consent suggests that it should be much, much lower.

Why?

Because of a 1989 report that said that “Before measles vaccine was available, more than 400,000 measles cases were reported each year in the United States. However, since virtually all children acquired measles, the true number of cases probably exceeded 4 million per year (i.e., the entire birth cohort).”

Their idea is that if there were more cases (i.e., the entire birth cohort), then even if almost 500 people died each year, the extra cases would make the death rate lower.

There are a lot of problems with that reasoning though…

For one thing, 500 people dying each year of a now vaccine-preventable disease is a lot of people, no matter how you to frame it!

I fixed this graph from The Physicians for Informed Consent to more accurately represent measles mortality data in the pre-vaccine era.
I fixed this graph from The Physicians for Informed Consent to more accurately represent measles mortality data in the pre-vaccine era.

And the traditional stat about the measles fatality rate clearly mentions that this is about reported cases.

You can’t change the number of measles cases to a theoretical number, the entire birth cohort, and keep the number of deaths based on the number of reported cases, and think that you are still talking about the same thing. What if deaths from measles were under-reported too?

“Death from measles was reported in approximately 0.2% of the cases in the United States from 1985 through 1992.”

CDC Pink Book

And there are plenty of more recent statistics, when far fewer people were getting measles, that show a similar case fatality rate.

What Is the Measles Fatality Rate?

How else do we know that The Physicians for Informed Consent is misinforming people?

“…any parent who has seen his small child suffer even for a few days with persistent fever of 105 F, with hacking cough and delirium, wants to see this prevented…”

Alexander D Langmuir, MD on the Medical Importance of Measles

Their measles ‘information’ sheet, made by folks who have likely never treated a child with measles, say that “most measles cases are benign.”

That’s a bit different than Dr. Langmuir’s 1962 account of how the typical child suffered with measles and why he welcomed the new measles vaccine.

“Nevertheless, a resurgence of measles occurred during 1989–1991, again demonstrating the serious medical burden of the disease. More than 55,000 cases, 123 deaths, and 11,000 hospitalizations were reported”

Orenstein et al on Measles Elimination in the United States

What was the case fatality rate during the measles outbreaks in the late 1980s?

It was a little over 0.2%. Did we again under-count cases or was the case-fatality rate so high because most of the cases were in younger, preschool age children?

Anyway, whether the case fatality rate is 1 in 1,000 or 1 in 10,000 (the UK lists their measles case fatality rate at 1 in 5,000), it doesn’t mean that someone will die when you hit case number 1,000, 5,000, or 10,000. It could be the 1st case in an outbreak or the 15,000th.

Measles can be deadly. That’s why most of us choose to have our kids vaccinated and protected.

Do you know how many people had measles in the 2013 outbreak in Brooklyn when a pregnant woman developed measles and had a miscarriage? The outbreak that was started by an unvaccinated teenager included a total of 58 cases.

How about the 2015 outbreak in Clallam County, Washington in which an immunocompromised woman died of pneumonia due to measles? There were only five other cases, almost all unvaccinated.

And in many European countries last year, many of the deaths are in countries with few cases. When the 17-year-old unvaccinated girl in Portugal died, there were just 31 cases. In Switzerland, a vaccinated man with leukemia died in an outbreak with just 69 cases. There were only 163 cases when an unvaccinated 10-month-old died in Bulgaria. And there were fewer than 1,000 cases in Germany when a partially vaccinated mother of three children died.

More Myths About Measles

The Physicians for Informed Consent pushes a lot of other myths and misinformation about measles:

  • about using vitamin A to treat measles – where this works, in developing countries, untreated measles has a case fatality ratio of 5 to 40% because of malnutrition! It isn’t usually thought to be very helpful in an industrial country without malnutrition. And no, simply having a picky eater or one who eats a lot of junk food doesn’t mean that he will be helped by vitamin A if he gets measles
  • about using immunoglobulin to treat measles – the MMR vaccine and immune globulin can be used for post-exposure prophylaxis, but it is not a treatment once you have measles!
  • they misuse VAERS data to try and say the MMR vaccine is more dangerous than getting measles
Not surprisingly, the information that The Physicians for Informed Consent provides rarely matches that of the references they cite.
Not surprisingly, the information that The Physicians for Informed Consent provides rarely matches that of the references they cite.

The Physicians for Informed Consent even talks about benefits of getting measles, but somehow leaves out any talk about the risk of getting SSPE after a natural measles infection.

What else do they leave out? The idea that people who survive a measles infection can have some immunosuppression for up to two to three years! This measles-induced immune damage puts them at risk of dying from other diseases and helps explain why kids who are vaccinated against measles are also less likely to die from other childhood infections.

They even published a press release claiming that they “recently reported in “The BMJ” that every year about 5,700 U.S. children suffer seizures from the measles, mumps and rubella (MMR) vaccine.”

Their report? It was a  “letter to the editor” that anyone can submit online…

Get educated so that you aren’t fooled by this kind of propaganda and anti-vaccine talking-points.

What to Know About Measles Propaganda from The Physicians for Informed Consent

The Physicians for Informed Consent push propaganda to make you think that vaccine-preventable diseases, like measles, aren’t that bad and that vaccines are really, really dangerous.

More on Measles Propaganda from The Physicians for Informed Consent

The First Measles Case of 2018 is at IU Bloomington

And the first measles case of 2018 is in…

  • Bloomington, Indiana

Unvaccinated children exposed to measles are quarantined for at least 21 days.

A student at Indiana University in Bloomington was diagnosed with measles on January 6.

The student may have exposed others between the time they arrived on campus on January 2, moved into her dorm (McNutt Residence Hall), and got diagnosed on January 6.

Fortunately, classes haven’t started yet, so exposure to others might have been lower than they typically might have been.

She likely did expose others on January 2:

  • on a flight from Mumbai, India to Newark Liberty International Airport
  • during a layover in Newark Liberty International Airport
  • on a flight from Newark to Indianapolis International Airport
  • at Indianapolis International Airport

Because measles has a long incubation period, remember that it might not be until January 23 that you develop symptoms if you were exposed are not immune (two doses of vaccine or natural immunity).

Indiana Measles Outbreaks

Surprisingly, this is not the first case of measles at this campus in recent years. Just four years ago, another student at Indiana University Bloomington was diagnosed with measles.

Or maybe it shouldn’t be so surprising.

Indiana has had some large measles outbreaks triggered by unvaccinated travelers returning to the state.
Indiana has had some large measles outbreaks triggered by unvaccinated travelers returning to the state.

There has been a lot of measles in Indiana in recent years:

  • an outbreak caused by an unvaccinated traveler who got 13 other people sick in 2011
  • another outbreak in 2012, also triggered by an unvaccinated traveler, also got 13 other people sick

In fact, since 2010, there have been at least 34 cases of measles in Indiana, including the latest case at IU Bloomington. Almost all have been unvaccinated.

And that’s with a pretty good vaccination rate.

Why?

Pockets of susceptibles, or so-called clusters of unvaccinated people, who get measles and then put the rest of us at risk.

Get educated.

Stop the outbreaks.

Vaccines work. Vaccines are safe and vaccines are necessary.

What to Know About Measles in Indiana

Indiana has been one of the states where we have seen measles outbreaks linked to clusters of unvaccinated people and is home to the first measles case of 2018.

More on Measles in Indiana

Updated January 13, 2018

Quarantine Signs for Vaccine-Preventable Diseases

If everyone breezed through vaccine-preventable diseases so easily back in the pre-vaccine era, then why were so many folks held under quarantine?

Quarantine Sign

Vaccine-preventable diseases have always been known to be dangerous and life-threatening.

If they were once thought of as a way of life, it was only because there was no way to avoid them!

As someone with an uncle who developed severe paralytic polio disease a few years before the first vaccine was developed, I can tell you that these diseases were no walk in the park.

Still, while quarantines are helpful to control disease outbreaks, they clearly aren’t enough. That’s evident by the way that vaccines were used in Leicester to control smallpox, even though some folks say it was all due to quarantines. It wasn’t.

How long would quarantine last?

Usually through at least one incubation period for the disease.

Quarantine Signs
Smallpox quarantine sign A Board of Health quarantine poster warning that the premises are contaminated by smallpox.
Diphtheria quarantine sign. Diphtheria quarantine sign.
Polio quarantine sign Polio quarantine sign.
In the pre-vaccine era, we had outbreaks of polio, and other, now vaccine-preventable diseases. Whooping cough quarantine sign.
Unvaccinated children exposed to measles are quarantined for at least 21 days. Mumps quarantine sign
Chickenpox quarantine sign Rubella quarantine sign.

Have you ever seen any of these quarantine signs?

If so, have you seen any of them lately?

That’s because vaccines work.

What to Know About Quarantine Signs for Vaccine-Preventable Diseases

In the pre-vaccine era, quarantines were the only way to try and help stop many diseases from spreading in the community.

More on Quarantine Signs for Vaccine-Preventable Diseases

The Benefits and Risks of Delaying Vaccines

Believe it or not, some pediatricians think it is a good idea to delay vaccines.

“Wait until a child is clearly developmentally “solid” before vaccinating because we just don’t know which children will react badly to immunizations.”

Dr. Jay Gordon

In fact, Dr. Bob wrote a whole book pushing his own immunization schedule!

Not surprisingly, there are no benefits to skipping or delaying your child’s vaccines, but there are plenty of risks.

What Are the Risks of Delaying Vaccines?

Of course, the biggest risk of delaying your child’s vaccines is that they will get a disease that they could have been vaccinated and protected against.

“In 1989, the Haemophilus influenzae type b vaccine was relatively new and not yet routine. I was aware of the vaccine’s availability, but, busy mom that I was, I had not yet made the trip to the health department to get the immunization for my two-year-old daughter, Sarah. I will always regret that bit of procrastination and the anguish that it caused.”

Peggy Archer

Although we are much more used to hearing vaccine injury scare stories, if you are thinking of delaying your child’s vaccines, there are also many personal stories of parents who regret not vaccinating their children that you should review.

You can wait too long to get a tetanus shot...
You can wait too long to get a tetanus shot… Photo by Petrus Rudolf de Jong (CC BY 3.0)

It is true that the risk may be very small for a disease like polio, which is close to being eradicated worldwide, but it is not zero.

Consider that the last case of polio occurred in 2005, when an unvaccinated 22-year-old U.S. college student became infected with polio vaccine virus while traveling to Costa Rica in a university-sponsored study-abroad program.

So you might not get wild polio unless you visit specific regions of Afghanistan or Pakistan, but you might want to be concerned about vaccine-associated polio if you go to a country that is still giving the oral polio vaccine.

And the risk is certainly much higher than zero for most other vaccine-preventable diseases, as we see from the regular outbreaks of measles, mumps, and pertussis, etc.

Some studies even suggest that delaying your child’s vaccines puts them at more risk for side effects once you do start to get caught up!

“…in the second year of life, delay of the first MMR vaccine until 16 months of age or older resulted in an IRR for seizures in the 7 to 10 days after vaccination that was 3 times greater than if administration of MMR vaccine occurred on time.”

Hambridge et al on Timely Versus Delayed Early Childhood Vaccination and Seizures

Why would that be?

It’s probably because that’s when kids are most at risk for febrile seizures.

What Are the Benefits of Delaying Vaccines?

Again, there are no real benefits of delaying vaccines, except that your child gets out of one or more shots. Of course, that means your unvaccinated child is left unprotected.

And it is going to mean more shots later, once you do decide to get caught up.

Will it mean a lower risk of autism, ADHD, eczema, peanut allergies, or anything else?

Nope.

“The prevalence of allergic diseases and non-specific infections in children and adolescents was not found to depend on vaccination status.”

Schmitz et al on Vaccination Status and Health in Children and Adolescents Findings of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS)

Unvaccinated kids are not healthier than those who are vaccinated. They are just at higher risk of getting a vaccine-preventable disease.

Why do some folks think that there are benefits to delaying vaccines? Because they have been scared into thinking that vaccines are harmful and that they don’t even work.

“I also warn them not to share their fears with their neighbors, because if too many people avoid the MMR, we’ll likely see the diseases increase significantly.”

Dr. Bob Sears in The Vaccine Book

Obviously, that put us all at risk. If too many people skip or delay their child’s vaccines, we will see more outbreaks.

Get educated. Vaccines work. Vaccines are safe. Vaccines are necessary.

What to Know About the Risks of Delaying Vaccines

Delaying your child’s vaccines offers no benefits and lots of increased risks, especially an increased risk of getting the diseases that the vaccines protect us against.

More on the Risks of Delaying Vaccines

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.

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