Flu Vaccines, Herd Immunity, and Randomized Trials

[indigo girl]

The latest study on flu vaccine effectiveness in children has been well discussed in the MSM and the flu blogs, so I'll point you to those excellent pieces (Branswell, crof, Mike Coston at Avian Flu Diary) and just add some things not covered elsewhere. The full text of the article is available for free at JAMA and it's a pretty good read, so if you want to see for yourself what is involved I urge you to read it, too. First, let me back up a bit and connect this to the controversy about observational and randomized clinical trials we've been discussing here of late (before my grant writing interfered, anyway).

There is ample evidence, both biological and observational, that immunization for seasonal influenza "works." But how well does it work? And what is the best way to do it? This is not just a scientific question (although it is a scientific question) but also a policy question. If it doesn't work at all or only minimally, then the policy of many national health departments is misguided and possibly dangerous. The question of whether flu vaccination works has been raised by (in our view) misguided zealots who demand standards of proof difficult to obtain (blinded and randomized trials) under the guise this is the only acceptable kind of evidence. We have previously registered our disagreement with this view (here, here), not least because even the availability of this evidence won't answer the questions. In fact reading some of the literature and commentary about this makes us wonder if the RCT zealots even understand why randomization is useful (and when possible, it is; see here, here, here, here, here, here). Just as importantly, the JAMA study illustrates why RCTs won't answer the question. More about that in a moment.

A quick synopsis of the JAMA study (you can read more details in the paper itself or in the linked articles, above). Suppose you wanted to do a randomized trial of whether vaccinating children protects unvaccinated older adults (on the theory that the children are good spreaders of the virus). How would you do a randomized trial of a community, not of the people in it? The beauty of the JAMA paper is that the authors found a way to do that, using fairly isolated and self-contained colonies of an Anabaptist fundamentalist sect in Canada, the Hutterites (I guess it shows that religious extremism is good for something). Instead of randomizing people, they randomized the colonies, vaccinating the children in some against flu, in others against hepatitis A. Not every Hutterite colony wanted to participate and many refused or dropped out after initially agreeing (but before allocation to either vaccine). Look at Figure 1 in the paper for the reasons why some colonies were included or not. It's a little lesson in how difficult these things are to do. Moreover this is a highly unusual situation and would simply not be feasible in almost any other set of communities. So good for these researchers for taking advantage of this opportunity. It's one of the things that makes epidemiology as much an art as a science.

More at: http://scienceblogs.com/effectmeasure/2010/03/flu_vaccines_herd_immunity_and.php

The Editors of Effect Measure are senior public health scientists and practitioners. Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799). The Editors sign their posts "Revere" to recognize the public service of a professional forerunner better known for other things.

[aeauooo]

Indigo Girl (not to be confused with Indigo Mom): H1N1 warrior - and God bless you for it!

[indigo girl]

Indigo Girl (not to be confused with Indigo Mom): H1N1 warrior - and God bless you for it!

Thanks aeauooo, but it is influenza itself, particularly pandemic flu that is my main interest, but, thanks for coming along for the ride! I can't seem to help but be fascinated by this topic. Watching mainly bird flu, H5N1 for a long time, & it's very worrisome.

I will admit to a great interest in other communicable diseases as well...

[aeauooo]

Thanks aeauooo, but it is influenza itself, particularly pandemic flu that is my main interest, but, thanks for coming along for the ride! I can't seem to help but be fascinated by this topic. Watching mainly bird flu, H5N1 for a long time, & it's very worrisome.

I realized your interest extends far beyond H1N1 after I posted my comment.

I'm currently working for the Louisiana OPH in H1N1 (a job I don't expect to last much longer). I have to admit that, although flu is fascinating, it's really not my primary interest (as you can see from my profile). Nevertheless, my current position has allowed me to do a lot of reading on the subject, and your posts include some of my favorite sources and topics - I'm impressed!

I have a stack of papers on my desk on H5N1, but I've had top set them aside while I work on our after-action report. The general public really has no idea how serious of a threat it is.

Keep up the good work!