Tag: vaccine effectiveness

Everything You Need to Know About the Measles Vaccine

The measles vaccine is one of the most effective vaccines we have.

It is also one of the safest, having very few serious side effects.

Everything You Need to Know About the Measles Vaccine

So why are some parents still afraid to allow their kids to get vaccinated and protected, putting them at risk to get measles, a life-threatening disease?

“Existing evidence on the safety and effectiveness of MMR vaccine supports current policies of mass immunisation aimed at global measles eradication and in order to reduce morbidity and mortality associated with mumps and rubella.”

Cochrane Systematic Review on Vaccines for measles, mumps and rubella in children

Let’s see if you still are after we get all of your questions about the measles vaccine answered…

Schools in California were closed for at least two weeks in 1917 because of measles epidemics.
Schools in California were closed for at least two weeks in 1917 because of measles epidemics.
  1. How long has the measles vaccine been around? The very first measles vaccine was licensed by John Enders in 1963. An improved measles vaccine was developed by Maurice Hilleman and licensed in 1968, and that is the measles vaccine that we still use today, at least in the United States. It was combined into the MMR vaccine in 1971.
  2. How effective is the measles vaccine? A single dose of the measles vaccine is about 93% effective at preventing a measles infection. Two doses (the second dose was added to the routine immunization schedule in 1994) are up to 97% effective. That’s why almost all of the people who get measles in an outbreak are unvaccinated.
  3. How long does immunity from the measles vaccine last? Immunity from the measles vaccine is thought to be life-long. It is important to understand that the second dose isn’t a booster dose, but is instead for those few folks who don’t respond to the first dose.
  4. Who should get the measles vaccine? Everyone without a true medical contraindication should get the measles vaccine (MMR), with the first dose at 12-15 months and a second dose at 4-6 years.
  5. Can my kids get their measles vaccine early? An advanced immunization schedule is available for kids in an outbreak or if they will be traveling out of the country. The first dose can be given as early as age 6-months, but is repeated when the child is 12 months because of concerns of interference with maternal antibodies. The official second dose can be given early too, as early as 4 weeks after the first dose, as long as the child is at least 12 months old.
  6. Do I need a booster dose of the measles vaccine? People who are fully immunized do not need a booster dose of the MMR vaccine, but it is important to understand whether or not you are really fully immunized to see if you need a second dose. Some adults who are not high risk are considered fully vaccinated with only one dose, while others should have two doses. Are you at high risk to get measles? Do you travel, live in an area where there are measles outbreaks, go to college, or work as a health care professional?
  7. Should I check my measles titers? In general, it is not necessary to check your titers for measles. If you haven’t had two doses of the MMR vaccine, then get a second dose. If you have had two doses of the MMR vaccine, then you are considered protected. Keep in mind that there is no recommendation to get a third dose of MMR for measles protection, although it is sometimes recommended for mumps protection during a mumps outbreak.
  8. If my child gets a rash after getting his MMR, does that mean that he has measles? No. This is a common, very mild vaccine reaction and not a sign of measles.
  9. Can the measles vaccine cause seizures? The MMR vaccine can cause febrile seizures. It is important to remember that without other risk factors, kids who develop febrile seizures after a vaccine are at the same small risk for developing epilepsy as other kids. And know that vaccines aren’t the only cause of febrile seizures. Vaccine-preventable diseases can cause both febrile seizures and more serious non-febrile seizures.
  10. Why do people think that that the measles vaccine is associated with autism? It is well known that this idea originated with Andrew Wakefield, but the real question should be why do some people still think that vaccines are associated with autism after so much evidence has said that they aren’t?
  11. What are the risks of the measles vaccine? Like other vaccines, the MMR vaccine has mild risks or side effects, including fever, rash, and soreness at the injection site. Some more moderate reactions that can rarely occur include febrile seizures, joint pain, and a temporary low platelet count. More serious reactions are even rarer, but can include deafness, long-term seizures, coma, or lowered consciousness, brain damage, and life-threatening allergic reactions.
  12. Why are there so many reports of measles vaccine deaths? There are extremely few deaths after vaccines. The reports of measles vaccine deaths you see on the Internet are just reports to VAERS and are not actually reports that have been proven to be caused by a vaccine. As with other vaccines, the risks from having a vaccine-preventable disease are much greater than the risks of the vaccine. The only reason that it might not seem like that now is because far fewer people get measles now than they did in the pre-vaccine era, when about 500 people died with measles each year.
  13. When did they take mercury out of the measles vaccine? Measles vaccines, including the MMR, have never, ever contained mercury or thimerosal.
  14. Why do we still have outbreaks if we have had a measles vaccine since 1963? In the United States, although the endemic spread of measles was declared eliminated in 2000, many cases are still imported from other countries. As measles cases increase around the world, that is translating to an increase in outbreaks here. Even though overall vaccination rates are good, because there are many pockets of susceptible people in areas that don’t vaccinate their kids, they get hit with outbreaks.
  15. Can we eradicate measles? Because measles is so contagious, the vaccine does have failures, and some folks still don’t get vaccinated, there is some doubt that we can eradicate measles without a better vaccine. That doesn’t mean that the current measles vaccines can’t prevent outbreaks though…

Are you ready to get your kids their MMR vaccine so that they are vaccinated and protected against measles, mumps, and rubella?

If not, what other questions do you have?

While you are thinking, here is a question for you – Do know why they used to call measles a harmless killer?

More on the Everything You Need to Know About the Measles Vaccine

Is My Fully Vaccinated Child at Risk from Your Unvaccinated Kids?

Parents who skip or delay their own child’s vaccines often seem surprised that the rest of us are so concerned about their decision.

If vaccines work, they say, why do we care if their kids aren’t vaccinated?

Vaccines are protecting our kids, so they shouldn’t be at risk, right?

“Think of camping as an analogy. If everyone at a campground properly stores their food, bears won’t be enticed to come around. If even one person leaves their food unprotected, it invites bears in to investigate all the campsites for opportunities to eat.”

How does choosing not to immunize affect the community?

Of course, the issue isn’t just the risk to our fully vaccinated kids, but also the risk to those who are too young to be vaccinated, too young to be fully vaccinated, and those who can’t be vaccinated because of true medical contraindications.

In addition to those who are intentionally unvaccinated, these others often get caught up in outbreaks of vaccine-preventable diseases.

Is My Fully Vaccinated Child at Risk from Your Unvaccinated Kids?

But there is also a risk to those who are fully vaccinated, and no, that doesn’t mean that vaccines don’t work.

It just means that they don’t work 100% of the time.

And most of us don’t think that your vaccine choice should put our kids at extra risk.

Anti-vaccine propaganda pushes some folks to make bad decisions about vaccines.
Anti-vaccine propaganda pushes some folks to make bad decisions about vaccines.

Did you hear about the one measles outbreak in 2011 that was started by someone who was fully vaccinated?

“She had documentation of receipt of MMR vaccination at 3 years and 4 years of age. There was no travel during the incubation period and no known sick contacts. However, the index patient worked at a theater frequented by tourists.”

Outbreak of Measles Among Persons With Prior Evidence of Immunity, New York City, 2011

The thing about that outbreak, is that of the 222 cases that year, she was the only one known to be vaccinated. So she was almost certainly exposed to measles by someone who wasn’t vaccinated.

As someone who was fully vaccinated, is it fair that she got caught up in those outbreaks?

It is especially unfair that our kids are at extra risk for vaccine-preventable diseases because some folks make a decision to leave their kids unvaccinated and unprotected because they believe anti-vaccine misinformation like:

  • you have nothing to worry about because your child is vaccinated – again, vaccines aren’t 100% effective, so there is still some risk until a disease is finally eradicated
  • someone who is vaccinated could also get your child sick – yes, but someone who is vaccinated would be less likely to get sick than someone who is unvaccinated
  • vaccinated kids are shedding virus, making everyone sick – no, they aren’t, not even during “shedding season
  • getting vaccinated doesn’t prevent disease, it just makes it so you have fewer symptoms, but you still get others sick – in most cases, vaccines keep you from getting sick altogether – they so prevent disease in most cases, but yes, if you still got sick, you will likely have milder symptoms than if you were completely unvaccinated
  • you can’t spread a disease you don’t have – that’s true, but if you are unvaccinated and unprotected, you are at much higher risk to get these diseases and then spread them to others
  • vaccines don’t prevent diseases from spreading anyway – if you don’t get a disease because you are vaccinated, you aren’t going to spread it
  • getting vaccinated just turns you into a carrier – this is about the study in baboons, but it doesn’t mean you shouldn’t get vaccinated

What about the idea that you will just keep your unvaccinated kids home if they do catch something?

What are the chances that you could be exposed to measles during an outbreak?
What are the chances that you could be exposed to measles during an outbreak?

Looking at all of the places that the folks in the Clark County measles outbreak exposed others, it should be clear that waiting to quarantine your child if they get sick isn’t very effective.

What’s the problem?

An infant with measles during the 2014 outbreaks in the Philippines.
An infant with measles during the 2014 outbreaks in the Philippines. Photo by Jim Goodson, M.P.H.

With many diseases, you are contagious before you show symptoms. That is especially true with a disease like measles, when you may not even realize it is measles until you finally break out in a rash, after having 3 to 5 days of high fever.

That’s why it is important to vaccinate and protect your kids. When you skip or delay a vaccine, it is not just your own family that you are putting at risk.

More on Risks from Unvaccinated Kids

Propaganda Busting Confirms Anti-vaccine Sites Photoshop Images

Spend a few minutes going through our list of anti-vaccine PRATTs, and you will quickly realize that they just push misinformation and propaganda.

Propaganda Busting Confirms Anti-vaccine Sites Photoshop Images

How easy is it to refute their claims?

Consider this “article” about measles outbreaks

It shows an infant with chicken pox.

While that could be a simple mistake, it is actually a Photoshopped stock image of an infant with chicken pox that adds a big scary needle and syringe, that I guess is supposed to represent a vaccine.

Where's the syringe and needle?
Where’s the syringe and needle?

The thing is, neither the chicken pox nor MMR vaccine look like that and neither would be given with such a long needle!

In fact, that needle is about twice the size as any needle that would be used on an infant or toddler, which is why they had to Photoshop a separate photo of a big syringe and needle onto the infant with chicken pox.

It's just a stock image of a big syringe and needle...
It’s just a stock image of a big syringe and needle…

Now that you know that the photo is make-believe, you shouldn’t be surprised that their “article” is too.

This erroneous thinking has led the public, media and government alike to attribute the origin of measles outbreaks, such as the one reported at Disney in 2015 (and which lead to the passing of SB277 that year, stripping vaccine exemptions for all but medical reasons in California), to the non-vaccinated, even though 18% of the measles cases occurred in those who had been vaccinated against it — hardly the vaccine’s two-dose claimed “97% effectiveness.”

Government Research Confirms Measles Outbreaks Are Transmitted By The Vaccinated

By itself, the number of cases in an outbreak doesn’t exactly tell you a vaccine’s effectiveness. You also have to know something about how many people were vaccinated and unvaccinated and the attack rate, etc.

“Among the 110 California patients, 49 (45%) were unvaccinated; five (5%) had 1 dose of measles-containing vaccine, seven (6%) had 2 doses, one (1%) had 3 doses, 47 (43%) had unknown or undocumented vaccination status, and one (1%) had immunoglobulin G seropositivity documented, which indicates prior vaccination or measles infection at an undetermined time.”

Measles Outbreak — California, December 2014–February 2015

Anyway, in the Disneyland outbreak, if you do the math correctly, you can see that only 8 of 110 were fully vaccinated, or about 7%.

What does that tell you about vaccine effectiveness?

Not much!

Again, we don’t know how many vaccinated vs unvaccinated folks were exposed and didn’t get measles.

We can guess though…

Most folks are vaccinated, even in California. So the fact that only 7% of the people that got measles in the outbreak were fully vaccinated actually says quite a lot about how effective the MMR vaccine really is.

What about the idea that vaccinated people are starting outbreaks and spreading measles?

While the vast majority of measles outbreaks are in fact traced to someone who is unvaccinated, there was one outbreak in 2011 that was “started” by someone who was vaccinated.

“She had documentation of receipt of MMR vaccination at 3 years and 4 years of age. There was no travel during the incubation period and no known sick contacts. However, the index patient worked at a theater frequented by tourists.”

Outbreak of Measles Among Persons With Prior Evidence of Immunity, New York City, 2011

Since even the MMR vaccine isn’t 100% effective, is it really so surprising that occasionally, someone who received two doses of the vaccine could get measles and pass it to others, especially considering that around 220 people got measles in the United States that year?

“During 2011, a provisional total of 222 measles cases were reported from 31 states… Most patients were unvaccinated (65%) or had unknown vaccination status (21%). Of the 222, a total of 196 were U.S. residents. Of those U.S. residents who had measles, 166 were unvaccinated or had unknown vaccination status, 141 (85%) were eligible for MMR vaccination, 18 (11%) were too young for vaccination, six (4%) were born before 1957 and presumed immune, and one (1%) had previous laboratory evidence of presumptive immunity to measles.”

Measles — United States, 2011

Is the MMR vaccine a failure because there were some still some outbreaks in the 1980s, before we started to give kids a second dose? The attack rate in many of these school outbreaks, in which many kids had one dose of MMR, was still only about 2 to 3%.

It is safe to blame a failure to vaccinate and intentionally unvaccinated kids for most of the recent measles outbreaks.

Is the MMR vaccine a failure because we still have outbreaks among intentionally unvaccinated kids and every once in a while, in someone who is fully vaccinated who gets caught up in an outbreak?

Of course not!

It is easy to do a little research, consider what disease rates looked like in the pre-vaccine era, and know that vaccines work and that they are necessary.

More on Propaganda Busting Confirms Anti-vaccine Sites Photoshop Images

Can I Get a Second Flu Shot for Extra Protection?

If one flu shot is good, wouldn’t two be better?

Can I Get a Second Flu Shot for Extra Protection?

Some people do get a second flu shot.

In fact, all kids eight years and younger, if it is their first time getting a flu vaccine, get two doses of flu vaccine.

How many doses of flu vaccine will your kids need this year?
How many doses of flu vaccine will your kids need this year?

The first dose is a priming dose and the second, at least 28 days later, is a booster dose.

Why do we do it that way?

Because studies have shown that is the best way to do it.

We don’t need to use this same priming/booster strategy in older children and adults though.

But with recent talk that protection against the flu after a flu vaccine might wane before the end of a flu season, some folks are likely wondering if they should just get another flu shot later in the season.

“Revaccination later in the season of persons who have already been fully vaccinated is not recommended.”

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season

And the official answer is no, except for younger children getting vaccinated for the first time, you should just get one dose per season.

Why not?

Mostly because a lot of studies haven’t been done to see what effect that second dose will have. And since some studies have even suggested that regular annual flu vaccines could actually lower vaccine effectiveness, you would want to know if getting an extra flu vaccine was safe and effective before we started to do it.

Not surprisingly, someone has looked into this already. One small study, Influenza revaccination of elderly travelers: antibody response to single influenza vaccination and revaccination at 12 weeks, actually showed that a second dose in the same season “did not enhance the immune response.”

So just one flu vaccine per season.

“Prior-season vaccination history was not associated with reduced vaccine effectiveness in children, supporting current recommendations for annual influenza vaccination of children.”

McLean et al on Association of Prior Vaccination With Influenza Vaccine Effectiveness in Children Receiving Live Attenuated or Inactivated Vaccine

But do get a flu vaccine every season.

Again, while there were some reports that an annual flu vaccine could lower vaccine effectiveness, other studies have disproven this.

More on Getting a Second Flu Shot

Is This Year’s Flu Vaccine Working?

Breaking News – Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness have now been released (see below)

Flu season is just getting started, but I’m sure that you have already heard folks rating how well this year’s flu shots are working.

Are flu vaccines working well?
Are flu vaccines working well?

Of course, if you had a flu shot and have already gotten the flu, then you’re gonna think the flu shot isn’t working very well at all.

And if you are vaccinated and protected and have avoided the flu, then it is working so far, right?

Is This Year’s Flu Vaccine Working?

While we won’t know how well this year’s flu vaccine is working until the CDC releases the preliminary estimates on flu vaccine effectiveness, there are some good signs already.

  1. The majority of the influenza viruses collected from the United States so far have been “characterized antigenically and genetically as being similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses.”
  2. The most frequently identified influenza virus type reported by public health laboratories was influenza A(H1N1)pdm09 virus.

Remember, to be effective, you want the flu vaccine to match the strains of flu virus that are circulating in the community. A mismatch in flu virus strain or antigenic drifting leads to lower flu vaccine effectiveness (VE).

Remember the 2004-05 flu season? That was the year that because of a drifted A(H3N2) virus, “only 5% of viruses from study participants were well matched to vaccine strains.” And the flu vaccine wasn’t very effective at all.

Still, even when the flu vaccine matches circulating strains, in general, as we have certainly seen, “flu vaccines provide better protection against influenza B or influenza A (H1N1) viruses than against influenza A (H3N2) viruses.”

YearFlu Virus StrainVE
2004-05A(H3N2)10
2005-06A(H3N2)21
2006-07A(H1N1)52
2007-08A(H3N2)37
2008-09A(H1N1)41
2009-10A(H1N1)pdm0956
2010-11A(H3N2)60
2011-12A(H3N2)47
2012-13A(H3N2)49
2013-14A(H1N1)pdm0952
2014-15A(H3N2)19
2015-16A(H1N1)pdm0948
2016-17A(H3N2)40
2017-18A(H3N2)40
2018-19A(H1N1)pdm0947

So if you had to guess, you could probably say that this year’s flu vaccine is going to be at least 50% effective.

So just as good as flipping a coin? Not exactly.

There are a lot of benefits to getting a flu shot besides avoiding the flu, like avoiding severe flu, hospitalization, and death.

And since flu vaccines are safe and flu can be a life-threatening disease, even in those without any medical problems, wouldn’t you take any chance you could to reduce your child’s chances of getting sick?

When will we know how well this year’s flu vaccine is really working?

The CDC typically releases the first preliminary flu vaccine effectiveness report of the season in February.

Not that you should wait! Flu season is well underway and this is a great time to get a flu vaccine and get protected for the rest of flu season.

Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness

On schedule, the CDC has released this year’s Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness.

During this period, overall adjusted vaccine effectiveness against all influenza virus infection associated with medically attended ARI was 47% (95% confidence interval [CI] = 34%–57%). For children aged 6 months–17 years, overall vaccine effectiveness was 61% (44%–73%).

Interim Estimates of 2018–19 Seasonal Influenza Vaccine Effectiveness — United States, February 2019

That’s certainly better than we have seen in recent years.

More on the Effectiveness of This Year’s Flu Vaccine

Updated February 15, 2019

Flu Season Predictions

No, I can’t see into the future…

I predict that I will continue to get a flu shot each year, at least until they come out with a universal flu vaccine.
I predict that I will continue to get a flu shot each year, at least until they come out with a universal flu vaccine.

But some things are very easy to predict.

Flu Season Predictions

Here are some predictions for this year’s flu season.

  1. We will have a flu season epidemic in the United States this year. Surprised by that prediction? Don’t be. Flu activity reaches epidemic levels each and every year. What we don’t always have are flu pandemics, during which flu activity is very high in multiple parts of the world. By definition, flu season is an epidemic.
  2. Almost all states will eventually report having widespread influenza activity as flu season peaks. Again, this is not a bold prediction. It happens every year. How severe is flu season going to be? No one can really predict that, but we can look at the proportion of people seeing their health care provider for influenza-like illness (ILI) and laboratory-confirmed influenza-associated hospitalization rates as flu season moves along to get some idea. Remember, measures of the geographic spread of the flu don’t really tell you anything about the severity of flu activity.
  3. Dozens of kids will die with the flu – most of them unvaccinated. Remember, 37 kids died in the mildest flu season we had.
  4. A little under half of adults will get a flu vaccine, even though the current recommendation is that everyone who is at least six months old without a true contraindication get vaccinated each year.
  5. A little over half of parents will get their kids a flu vaccine.
  6. Some people who get a flu vaccine will still get the flu. You know the flu vaccine isn’t the most effective, but it still has plenty of other benefits, so even if you did still get the flu, hopefully you got a milder case, weren’t hospitalized, and didn’t die.
  7. Some people who get a flu vaccine and get the flu will blame their flu shot, even though it is well known that the flu shot can’t give you the flu.
  8. Many people who aren’t high risk will be prescribed Tamiflu. Or Xofluza, because it is new.
  9. Tens of thousands of adults will die with the flu. Even in a mild flu season, the flu is very deadly.
  10. Some folks will continue to push the idea that there is a vaginal spermicide in flu shots, even though that anti-vaccine talking point has been refuted a thousand times already.

What else can you predict about flu season?

Some folks will think it is too late to get a flu shot.

It isn’t.

Get your flu shot if you haven’t and get protected for the rest of flu season.

Another bold prediction? Elderberry syrup and Oscillococcinum are not going to help prevent or treat your flu symptoms.

More Flu Season Predictions

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?