Monday, September 20, 2010

Same old song, different year

In the news today there's a flood of articles about flu shots reducing heart attacks.   I've yet to find the original study but the news indicated British researchers reviewed charts and found a 21% decrease in the rate of heart attacks in people over 40 if they got the flu shot between september and mid november and a 12% decrease if they got the shot later in the year.  

This isn't new.  Last September stories like this were published 

Before that there have been studies showing a 50% to 90% decrease in mortality in elderly people who received the flu shot.  

All of these studies suffer from what's called "selection bias".   People who choose to get the vaccine,  especially elderly people, are more likely to seek medical care for their chronic conditions like high blood pressure or heart disease.   Influenza doesn't account for more than 5% of deaths in the elderly and yet the shot somehow lowers mortality 50% or more?   Additionally some of these studies found the "benefits" growing the following summer after the shot and flu season were long gone.   

The theory that reducing the stress of the viral infection,  influenza, will prevent heart attacks makes sense to me but it is equally reasonable that the myriad other viral infections that replace it (in the minority of vaccination recipients who do benefit) will stress the system just as much if not more.   Influenza unlike a few other respiratory viruses isn't known to directly infect the heart muscle for example.  

It's flu season and the stories touting benefits to vaccination are coming out of the woodwork again.  

Here's a good summary of what we know about influenza from vaccinations to antiviral drugs.

This one specifically talks about the misleading results on mortality

gotta hit play on that one

So when you hear the flu shot prevents heart attacks say "that's selection bias bubba".  

Thursday, September 16, 2010

Blame Manichanh

My PA friend sent me this article from one of them PA magazines

It got me all riled up and my comment ended up being a pretty good overview of several vaccines so I gotta save it here.   You can stop reading now if you're not ready to spend like an hour thinking about this mess.

Are you serious?   How about instead of reading CDC reports and recommendations and parroting them to PAs,  we look at the actual clinical trials and quantify the benefits and risk of the vaccines you covered?  

PCV-7:  The 2 prelicensure trials show a decrease in IPD which becomes less pronounced over the short 3 year span of the studies.  There is a marked serotype replacement phenomenon that continues to be studied to this day.   PCV-7 was just mentioned in a JAMA article which reported a RCT showing serotype replacement with 19A nearly twice as often compared to unvaccinated controls.   Additionally there is zero mortality benefit demonstrated in any PCV7 clinical trial and the pneumonia benefits don't reach statistical significance unless the trial was outside of the US where attack rates are much higher.  
PCV7 isn't even recommended at this point with the new PCV13 taking its place.  There were no clinical trials used in the approval of PCV13 except for immunology studies which showed borderline responses for 3 of the 13 serotypes by the by.

Routine influenza vaccination was summarized so well by Cochrane that I've nothing to add: (in the eldery) (health care workers) ( patients with asthma) (swine flu and routine influenza vaccination) 

Why would you recommend routine influenza vaccine?  Is it because the CDC recommends it?  That is NOT evidenced based medicine.  It's expert opinion based medicine.  

As for adult vaccination with PPV23:   The results are underwhelming

I do like the baseball analogy.   PAs are like the designated hitter in the majors.  They're paid less but reap huge rewards for the team.  I agree it's time for the PAs to "step up to the plate" but only metaphorically speaking.   It is time for PAs to join their brothers and sisters watching the GAME from the stands.  It is they who pay your salary and it is they who you are duty bound to advocate for.   Stop playing the GAME and start examining the men behind the curtain.