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Vincent Iannelli, M.D.

Why So Many Pertussis Outbreaks?

By April 25, 2012

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Ever since the 2010 California pertussis outbreak, in which there were 9,154 cases of pertussis, the most in 63 years, and 10 infants died, many people, especially parents, are wondering why we are seeing more pertussis these days.

Is it because the pertussis vaccines simply don't work, as the anti-vaccine movement would have you think?

Or is it because there are higher rates of unvaccinated kids these days and parents using alternative immunization schedules, instead of the standard immunization schedule from the CDC?

A new commentary that will appear in the May issue of Pediatrics, "Why Do Pertussis Vaccines Fail?," may finally give us some answers.

While the title of the article might have you think that all of the blame lies with the pertussis vaccines, that certainly isn't the case. While there can be vaccine failures with the pertussis vaccines, just like any other vaccine, that doesn't mean that the vaccine doesn't work for most children.

One of the problems is that the DTaP vaccine likely doesn't work as well as the older DTP vaccine and likely doesn't work as well as we used to think it did. So instead of efficacy of 84 to 85%, as was once believed, it is likely closer to just 71 to 78%.

Other issues, including a decay in antibody to specific vaccine proteins over time, the possibility of an incorrect balance of antigens in the vaccine that could create a blocking effect, and genetic changes in the B. pertussis bacteria, could also possibly lead to increased vaccine failure rates.

So it isn't that the pertussis vaccine doesn't work. That should be easy to see when you look at the pertussis rates in California, when the highest rates by far were in infants less than 6 months of age (434 per 100,000 people). In contrast, children who were 6 months to 6 years old had a rate of only 62 per 100,000.

And the results of a study that were presented at the 49th annual meeting of the Infectious Diseases Society of America in Boston show just how important the pertussis vaccine is, as:

  • vaccine effectiveness was 98.1 percent among children who received their 5th dose within the past year
  • long term effectiveness - children who were five or more years past their last DTaP dose - was about 71 percent
  • children who had never received any doses of DTaP (unvaccinated children) faced odds of having whooping cough at least eight times higher than children who received all five doses

It is also important to note that the high rates seen in 2010 in California are still well below the rates that were seen in the prevaccination era, when the attack rate of pertussis in the United States was as high as 157 per 100,000 people, with about 200,000 cases a year.

What's the answer? It certainly isn't for more kids to follow alternative immunization schedules or to simply skip vaccines all together. Natural immunity isn't going to keep newborns and infants from getting pertussis, the ages which are most at risk for life-threatening infections, as they catch pertussis from people around them, including those working on their natural immunity. Natural infections don't even provide life-long protection against pertussis, as some people believe. That natural immunity wanes fairly quickly too.

The future of pertussis control more likely is going to be in maximizing our current vaccination program, including getting more teens and adults to get the Tdap vaccine. According to the CDC, in addition to protecting yourself and those people around you, "people who do catch whooping cough after being vaccinated are much less likely to be hospitalized or die from the disease."

Unfortunately, children who aren't vaccinated against pertussis can't "hide in the herd" and rely on the rest of us who do vaccinate our children to provide them with protection. Instead, since they are at a higher risk, they get pertussis and get the rest of us sick.

In a 2009 study that appeared in Pediatrics, researchers found that "vaccine refusers had a 23-fold increased risk for pertussis when compared with vaccine acceptors, and 11% of pertussis cases in the entire study population were attributed to vaccine refusal." And since pertussis is highly contagious, with every primary case typically infecting as many as 17 other people, it makes sense that higher rates of children using vaccine exemptions could be at least one of the factors in these outbreaks.

In fact, one article, "Geographic Clustering of Nonmedical Exemptions to School Immunization Requirements and Associations With Geographic Clustering of Pertussis," found that "geographic pockets of vaccine refusal are associated with the risk of pertussis outbreaks in the whole community."

The pertussis epidemic in California is over. They are back down to a state rate of less than 1.0 per 100,000 in 2012. Unfortunately, many other places are now seeing pertussis outbreaks, including:

  • Hillsborough County, Florida - 35 cases including a family with 6 unvaccinated children
  • Milwaukee County, Wisconsin - a cluster of 28 children at a private school and the death of a one month old in February
  • Bell, Waco-McLennan Counties, Texas
  • Polk County, Iowa - an increased number of cases in students, which prompted a vaccinated clinic in which 234 were vaccinated
  • San Luis Obispo County, California - two infants less than one month old have been found to have pertussis, an age that is at high risk for life-threatening infections
  • Cache County, Utah - an increased number of cases has been noted in the area, which many people will remember for their measles outbreak in unvaccinated children last year
  • Washington - which is experiencing a statewide epidemic of pertussis
  • Ravalli County, Montana - an outbreak is now up to 27 cases in the area and 115 unvaccinated children have been barred from coming to school for 21 days

And although it didn't make the news, the Dallas County Health Department informed me that a local newborn died of pertussis this month.

Why so many pertussis outbreaks? While experts continue to work on that question, my only real question is why are so many parents still not vaccinating their children?

As Alfred DeMaria, Jr., M.D. says in the article, "Accounting for Pertussis," the "resurgence of pertussis and measles in the U.S. reminds us, once again, of the need to maintain high levels of population immunity."

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April 25, 2012 at 3:14 pm
(1) G Vazquez MD says:

Dr Ianelli,
I am a member of the AAP as you probably are.
I believe they, as well as all pediatricians ,have a responsibility to not mince words and lay the blame for these epidemics where they lay;refusal to vaccinate in accordance with CDC vaccine schedule.
I’ve read too many articles that confuse the public by accusing everything from undocumented aliens and pertussis epidemic cycles to waning vaccine immunity in vaccinated people. Those factors have always existed but it took the Andrew Wakefield disaster and the Jenny McCartney campaign to frighten parents from vaccines.
The AAP and pediatricians need to make clear public statements about these epidemics and their cause in order to stop the spread of illnesses that should be history by now.

April 25, 2012 at 3:44 pm
(2) Vincent Iannelli, MD says:

“Those factors have always existed but it took the Andrew Wakefield disaster and the Jenny McCartney campaign to frighten parents from vaccines.”

I’m only going to disagree with you on one thing.

Antivaxers like to use the fact that many vaccinated kids get pertussis once immunity wanes when they get older, but as with outbreaks of mumps and other vaccine preventable diseases, that fails to take into consideration attack rates for vaccinated vs unvaccinated people. I think we will finally see more studies about the 2010 California outbreak highlighting that point in the next few months.

The point I disagree with you on is the influence of Wakefield and Jenny McCarthy. Except for the hard-core anti-vaxer who believes that vaccines cause autism, the real thing that likely kept the antivaccine movement going was the alternative vaccine schedule of Dr. Bob Sears.

Few parents know the other players in the anti-vaccine movement. They don’t know who Barbara Loe is anymore, which is why she is reduced to buying billboards in New York City and ads on airline flights.

The guy who was so concerned about mercury in vaccines is now writing about killer whales. Do they get vaccines too?

In a normal cycle of antivaccine activism and increased disease, after the increase of pertussis in 2005, we would normally have seen an increase in vaccination rates. Instead we got Dr. Bob’s book and increases in vaccine exemptions and more parents who aren’t vaccinating.

There is plenty of blame to go around, but some of it should go to the people who are feeding parents the misinformation that is influencing their decision to not protect their children by getting them vaccinated.

April 25, 2012 at 6:50 pm
(3) Joy says:

Question regarding this quote from your article:
“Instead, since they are at a higher risk, they get pertussis and get the rest of us sick.”
If you have the vaccine for pertussis, why would you get sick from someone who didn’t have the vaccine?

April 25, 2012 at 6:57 pm
(4) mrsculpepper says:

I would like to point out that some of us abstain from vaccines due to religious objections to the blood products found in so many of them.

April 25, 2012 at 7:35 pm
(5) Vincent Iannelli, MD says:

“I would like to point out that some of us abstain from vaccines due to religious objections to the blood products found in so many of them.”

Few people have a problem with those who have a true religious exemption to vaccines.

Many parents are abusing the religious exemption though, with anti-vaccine websites even offering parents hints and instructions on how to do it, so that they file a religious exemption even if getting vaccines doesn’t contradict with their sincere religious beliefs.

April 25, 2012 at 7:45 pm
(6) Vincent Iannelli, MD says:

“If you have the vaccine for pertussis, why would you get sick from someone who didnít have the vaccine?”

For one thing, as we saw in the California epidemic, the highest rates of disease, and the only deaths (10 infants), were in children too young to be fully vaccinated (usually with your 3rd dose of DTaP at 6 months of age).

That’s one good way to get sick from someone who didn’t have the vaccine.

A child (or adult) who is fully vaccinated might also develop cancer and require chemotherapy, which would affect their immune system and the ability to fight infections. These children, and children with many other immune system problems, are at great risk for getting sick from people who are not vaccinated.

And as we are seeing with the pertussis vaccine, the vaccine’s effectiveness wears off over time. If your immunity is wearing off and you are around someone with pertussis who wasn’t vaccinated, you are more likely to get sick.

The measles vaccine is a lot more effective, close to 99% after two doses, which is likely why we didn’t see many cases in vaccinated children during the recent measles outbreaks.

April 27, 2012 at 7:41 pm
(7) Liz Ditz says:

Dr. Iannelli and Dr. Vazquez,

While I agree that Bob Sears’s vaccination book has a lot to do with vaccine hesitancy, it didn’t start with him. Neil Z. Miller’s book was first published in 1992 and there were others. All of these were really popular with people who patronized “health food stores” and the like.

And don’t overlook “Mommy to Mommy” transmission of vaccine fears. For example, the Mothering DOT com boards are rife with anti-vaccination myths. Many there think that Bob Sears is too soft on vaccines. Just this afternoon, sitting in the coffee shop, I heard 2 moms of infants egging each other on in vaccine fears. (It’s still a fact, according to the eavesdropping victims, that the combination of mercury and measles virus in the MMR vaccine causes autism, and the CDC is covering it up. I bit my tongue hard to avoid butting in.)

April 27, 2012 at 8:48 pm
(8) Vincent Iannelli, MD says:

“Mothering DOT com boards are rife with anti-vaccination myths. Many there think that Bob Sears is too soft on vaccines”

While I agree that the anti-vax movement certainly isn’t new, going back all the way to when the first small pox vaccine came out, it seems a little different now.

Pediatricians have been seeing a lot more vaccine-hesitant parents and not just the truly anti-vax mothering.com or AOA types. Of course these vaccine-hesitant parents have been influenced by all of the misinformation from all of those forums, but it seems to me like the Dr. Sears book gave the anti-vax movement some credibility for them and likely pushed them over the edge in getting scared to skip vaccines.

April 28, 2012 at 6:45 am
(9) Ken says:

If you do not vaccinate due to religious reasons you are doubly foolish.

April 28, 2012 at 10:14 am
(10) Vincent Iannelli, MD says:

“If you do not vaccinate due to religious reasons you are doubly foolish. ”

I’d like to say that I don’t support that idea.

There don’t seem to be that many religions that are truly against immunizations:

Christian Scientists…

It is generally believed that Jehovah‚Äôs Witnesses are against vaccines, but their website says that “We have no objection to vaccines in general. Some vaccines contain minor blood fractions, and use of these is a matter of personal choice.”

Unfortunately, there are a lot of other misconceptions about religion and vaccines related to Catholics, Muslims, and Jews.

April 28, 2012 at 9:29 am
(11) Tsu Dho Nimh says:

Another reason is that – because of all the vaccinated people and the resultant low incidence of the VPDs – we aren’t being constantly re-challenged and getting those teensy sub-clinical infections that act like booster vaccinations.

April 28, 2012 at 9:54 am
(12) peter says:

Great article!

Part of the answer is the epidemic cycle. Whooping coug rates rise & fall, with peaks every 3 years. Which makes vaccination particularly important right now.

May 3, 2012 at 12:20 pm
(13) iris says:

Do your research. 92 percent of the people with whooping cough HAVE been vaccinated!!!! Quit spewing your fear mongering propaganda!!!!

May 3, 2012 at 5:32 pm
(14) Vincent Iannelli, MD says:

“Do your research. 92 percent of the people with whooping cough HAVE been vaccinated!”

The attack rate is more important than the number of kids who have been vaccinated.

And besides, further research has found that children who had never received any doses of DTaP (unvaccinated children) faced odds of having whooping cough at least eight times higher than children who received all five doses.

May 4, 2012 at 2:25 am
(15) Lou says:

Here is my theory on pertussis. It is based on epidemiology, human physiology and good old sweet pure LOGIC.

What do we know

o Almost all mothers tested have NO detectable vitamin D in their mothers milk

o We can therefore assume almost all newborns have NO vitamin D in their rapidly developing bodies.

o Vitamin D is absolutely CRITICAL for preborns and new newborns

o Most newborns are under extreme vitamin D deficiency stress.

o Vitamin D is absolutely critical to defend against lung infections


o Most pertussis deaths are the under six month of age group.

o Pertussis is an infection of the lungs

So you tell me what do these babies need “vaccinations” of vitamin D?

All you pediatricians, do you test your newborns for a vitamin D level of 60 ng/ml? Do you replete your newborns to 60 ng/ml. Do you find pertussis in your vitamin D repleted newborns? Do you find lung problems in your vitamin D repleted newborns? Do you find seasonal flu problems in your vitamin D repleted newborns?

Now that we have solved the pertussis problem pick up a physiology book and find out how the newborns brain uses vitamin D and how a lack of vitamin D is undoubtedly a factor in autism as is “vaccination”.

May 4, 2012 at 9:29 am
(16) Lou says:

“What’s the answer?”

Well to start how about double blind placebo controlled testing of any “vaccine” solution to the problem. Has the current DTaP been double blind placebo controlled tested? If so did the vaccine prove safe and effective at reducing pertussis? Or was the only testing of the DTaP for antigen production? Which antigen did the DTaP produce? Which variant(s) of the pertussis bacteria species is infecting the current batch of pertussis infections?

Sir I posit if we are to solve our pertussis problem we should reject “the vaccine is the answer” solution and get back to basic science.

The well known pertussis vaccine failure is making a mockery of Institutional Medicine.

Good science is predictive. I predict that once the SUN comes out and those millions of babies and youngsters manage to get some SUN despite the best efforts of their propagandized heliophobic mothers to keep them out of the sun, the incidences of pertussis, viral flu, seasonal flu, “lung problems”, pulmonary congestion and most other nonspecific lung disorders will DROP as they always do once the SUN comes out.

Gee do you think the SUN may be part of the solution to our LUNG problems?

July 20, 2012 at 9:12 pm
(17) Amy says:

She must be from the Republic of Boulder.

July 22, 2012 at 7:14 pm
(18) Scott Parrish says:

Lou you make some good points although I would suggest a 25(OH)D level of 40ng/ml is a more reasonable target based on existing research. If Dr. Iannelli and Dr. Vazquez would like to rehabilitate their reputations they will shortly post how Vitamin D produces LL-37 (cathelicidin) in the body, and that it has antimicrobial properties, and the importance of assessing ones’ levels. If 95% of the whooping cough cases had 25(OH)D levels between 5-25 ng/ml that would temporarily and thoroughly undermine their insistence on vaccination. Moreover, whereas they don’t know the 25(OH)D levels of the kids with pertussis anyways, they have no assurance in advocating for the pertussis vaccine.

January 23, 2013 at 7:42 am
(19) skeptic says:

hi i am someone who has been searching the web just curious about the subject. was wondering you said 92% of the people who had whooping cough were vacinated and people who didnt get vacinated were eight times higher to get it ? in that case it would be 92% that were not vaccinated not the other way around.also what about doctor dr.hilliman(do some reseach) who worked for Merk, saying there was alot of other viruses and other crap in vaccines? just curious i have never had h1n1 shot swine flu or any others in along time and i have never had a bad flu or cold in years in years. i had bad whooping cough all threw school when i was getting the shot and i had it every year and bad!!. wwasnt until i got into high school stopped getting the shots that the whooping cough eventually went away.. been great ever since … and of course you in the SCIENTIFIC MEDICINE industry would be saying .. of course you guys would never amit were you mad mistakes what would that say about are medical scientised..you’d keep it in the scientific community …im great no shots never will ..and never look back we were nautral creatures and natural fight these virus or die ..so is life .. i recommend you look for DR.hillimans interveiw and explian that NATURALNEWS.COM and alot of doctors that i talk to dont get flu shoots and get kemo thearpy.. just my thoughts would love to here your replys

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