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.
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.”
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
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.
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.
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.
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?
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.
The herd immunity threshold may need to be higher than the previously suggested 88%–92% to prevent community transmission and outbreaks of mumps.
Quinlisk on Mumps Control Today
Many of these outbreaks occur despite many of the cases having had two doses of the MMR vaccine. A third dose is sometimes recommended during these outbreaks.
That doesn’t mean that the MMR vaccine doesn’t work. After all, just compare today’s rates of mumps, even if they are a little higher than we would like, to pre-vaccine levels…
And in the biggest outbreak, in Arkansas, only 71% of people were up-to-date on their vaccines!
Of course, getting two doses of the MMR vaccine is still the best way to avoid mumps.
There is no general recommendations to get an extra shot, although a third dose of MMR during an outbreak was recently recommended by the ACIP. The recommendation has not yet been formally approved though.
A recent study that was published in the New England Journal of Medicine, Effectiveness of a Third Dose of MMR Vaccine for Mumps Outbreak Control, found a lower risk of mumps in those who got a third dose of MMR.
Not surprisingly, the study also found a much higher risk of mumps, with the highest attack rates, in those who were unvaccinated or who had just one dose!
Keep in mind that the MMR vaccine isn’t just for kids. Adults who didn’t have mumps when they were kids (or who were born before 1957, when most kids got mumps), should make sure they are vaccinated (at least one dose) and protected too.
And these outbreaks show that they are definitely still necessary. In the latest outbreak in Hawaii, where “has been confirmed in children and adults, both vaccinated and unvaccinated,” there have been at least “16 reports of complications due to mumps infection,” including orchitis and hearing loss.
What to Know About Mumps Outbreaks
Although mumps outbreaks are occurring among those who are vaccinated, you still have a much higher chance of getting mumps if you are unvaccinated and unprotected.