New study on effectiveness of pertussis vaccine

[carriebft]

reuters article:

http://www.reuters.com/article/lates.../idUSN22371634

CHICAGO, May 26 (Reuters) - One in 20 children whose parents do not get them vaccinated against whooping cough catch the highly contagious virus, researchers said on Tuesday.

Only one in 500 children who got vaccinated developed whooping cough in the study by Kaiser Permanente Colorado's Institute for Health Research.

The researchers said their government-funded study was the first to use medical records to confirm which children received immunizations and which ones did not -- and the subsequent rates of whooping cough, or pertussis.

The study:

http://pediatrics.aappublications.or...urcetype=HWCIT

CONCLUSIONS. 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. These findings stress the need to further understand why parents refuse immunizations and to develop strategies for conveying the risks and benefits of immunizations to parents more effectively.

[Evergreen]

I think the potential for flaws definitely exists in this study. My friend and I both had two year olds who came down with pertussis in 2005. She took her daughter to three different doctors and got a different diagnosis each time- bronchitis, crop, indoor allergies. No tests for pertussis until she listened to a recording of a cough on the internet compared it to her daughter's and demanded the pertussis test. They pooh-poohed her because her little one was up to date on vaxes. Finally she got the test done and it came up positive. How many other vaccinated children were misdiagnosed or not even tested?

[Jugs]

RESULTS. We identified 156 laboratory-confirmed pertussis cases and 595 matched controls. There were 18 (12%) pertussis vaccine refusers among the cases and 3 (0.5%) pertussis vaccine refusers among the controls. Children of parents who refused pertussis immunizations were at an increased risk for pertussis compared with children of parents who accepted vaccinations. In a secondary case-control analysis of children continuously enrolled in Kaiser Permanente of Colorado from 2 to 20 months of age, vaccine refusal was associated with a similarly increased risk of pertussis. In the entire Kaiser Permanente of Colorado pediatric population, 11% of all pertussis cases were attributed to parental vaccine refusal.

What were the other 89% attributed to? Vaccine failure?

[carriebft]

Many of the children who were not vaccinated or were behind were probably more due to apathy on the subject by the parents, missing appointments, monetary issues, etc-- the typical reasons for kids not being vaccinated in the USA, where we have pretty low intentional vaccine refusal (though growing, it is still not the #1 for a child missing vaccines)

Given the low number of vaccine refusal overall, 11% is quite a large number of cases attributable to that.

[emma1325]

At least we're seeing more studies which are moving in the right direction. Comparing vaccinated vs. non-vaccinated definitely needs to be seen, hopefully on a large-scale and comparing the long term health of vaxed vs. non-vaxed.

I wish this study would have addressed the question of whether or not the pertussis vax can prevent transmission or not.

[carriebft]

And when you look at the overall numbers with regards to that 11% figure, it translates to 1 in 20 unvaccinated kids getting pertussis whereas 1 in 500 vaccinated kids get it.


of course, we also know that the vaccine lessens symptoms, so that must be taken into account.

[emma1325]

Originally Posted by Jugs

What were the other 89% attributed to? Vaccine failure?

Also, I'd love to know, were there any serious complications/death from these cases of whooping cough? off to read the article better...

[carriebft]

Originally Posted by emma1325

At least we're seeing more studies which are moving in the right direction. Comparing vaccinated vs. non-vaccinated definitely needs to be seen, hopefully on a large-scale and comparing the long term health of vaxed vs. non-vaxed.

I wish this study would have addressed the question of whether or not the pertussis vax can prevent transmission or not.

They do mention it:

Herd immunity does not seem to completely protect unvaccinated children from pertussis.

[Jugs]

But in the case of vaccine refusal, the parent is usually aware that their child is at an increased risk of pertussis, and is making the choice to take that risk over the risks attributed to the vaccine. Heck, my 4-year-old was one of the 1 in 500 stat who got pertussis anyway

[carriebft]

Originally Posted by Jugs

But in the case of vaccine refusal, the parent is usually aware that their child is at an increased risk of pertussis, and is making the choice to take that risk over the risks attributed to the vaccine. Heck, my 4-year-old was one of the 1 in 500 stat who got pertussis anyway

That may be the case for some, others don't see it that way. I would say that it's 50/50 from what I see here between those who feel there is no increased risk because the vaccine doesn't work and those who feel pertussis isn't a big deal so increased risk isn't an issue.

[carriebft]

Better info on what is meant by that 11% figure:

The percentage attributable risk in the vaccine refuser population was 99.5% (95% CI: 98.1%-99.9%), and the total population attributable risk was 11.0% (95% CI: 5.8%-16.0%). These estimates suggest that all 18 of the unvaccinated pertussis cases were attributed to vaccine refusal, and 11% of the pertussis cases in the total population were associated with vaccine refusal.

There are some blogs out there that have gotten ahold of the whole study...though they are not exactly the 'nice' ones, if you know what I mean. But, for example Orac, seems to have the full text and has posted on the bit concerning herd immunity as well.

[Jugs]

I would say the "It doesn't work" camp is more along the lines of "It doesn't work as well as, or the way we're being told it does"

[Jugs]

Originally Posted by carriebft

Better info on what is meant by that 11% figure:

Okay, that makes more sense. However, the very fact that petussis is so greatly underdiagnosed among the vaccinated is enough to call the stats into question.

[kiara7]

Pertussis case status and vaccination status were ascertained by medical chart review.

Does someone have access to the full study so we can see everyone's vax status?

[carriebft]

some bloggers over at science blogs and respectful insolence as well seem to have it in full and are quoting and posting the charts (edit: not the medical charts of the patients but the tables in the study I mean). I don't have access though I won't link those blogs as they can cause some anger.

[kiara7]

They only have one table, and not the right one of course.

[anewmama]

Originally Posted by Jugs

Okay, that makes more sense. However, the very fact that petussis is so greatly underdiagnosed among the vaccinated is enough to call the stats into question.

How do you figure this? The way I read Carrrie's thread starter (have not yet read the article), they are talking about WC cases confirmed here by medical records. They are not talking about populations at large so underdiagnosed is releveant.

They are not talking about people in "general", only those with confirmed cases and confirmed vaccine status among the study of medical records. If this is the case, and it might not be, not sure how the study was actually done, then underdiagnosed is irrelevant to this specific information. Not that it's irrelevant to the overall picture or to your decision making, but this is just a study of diagnosed cases.

I mean we can't have it both ways, no? You want to compare under vaxed to vaxed, this seems to be a step that way, right? But then you can throw out the whole data because it's not looking at all those other known unknowns, KWIM?

[Jugs]

^^But that's my whole point: I'm not saying its completely useless, but that its not indicative of the true risk of contracting pertussis, based on vaccination status.

[anewmama]

So I am reading on Orac's blog a bit more about the stats. No, it's not the 'true risk'. However, it very might well be more reflective of the reality of the shot versus some of the "it doesn't work" statements. How much more the study improved the effectiveness over the later statement ("it doesn't work"), I am not sure.

[ema-adama]

I am thinking that if children who are vaccinated go to the doctor with a cough, the doctor is not going to think of pertussis as a possibility and so will not request a laboratory diagnosis, making the true number of vaccinated children diagnosed with pertussis *potentially* larger than is reflected in this study. You cannot have a confirmed case in the medical records if the doctors are not asking for the lab work to be done.

But then again, I am not worried about my son getting WC and was not relying on herd immunity to protect him.