Wednesday, October 14, 2009

Why Vaccines Matter


# 3834



I’ve just finished reading Do Vaccines Matter?  which appears today in the November issue of  The Atlantic Online.   In it, the authors  Shannon Brownlee and Jeanne Lenzer ask a number of important questions about the efficacy of flu vaccines and antivirals.


It’s a thought provoking piece, and I would urge you to read it. 


No doubt, a number of people upon reading this article will come away exclaiming, “Aha!  You see . . . I KNEW vaccines and antivirals were worthless.” 


But of course, it isn’t quite that simple.  And before you reach that conclusion, I would invite you to read on.


I know of no one in medicine who believes that flu vaccines and antivirals are a panacea for influenza (seasonal or pandemic).  


That is, and always has been, a straw-man argument. One put up by their opponents just so they can knock them down.  


Vaccines and antivirals aren’t perfect.  Not even close.  They are simply the best weapons we currently have in our (admittedly limited) arsenal against the influenza virus.


The effectiveness of flu vaccines compares poorly when viewed alongside other vaccines, such as measles or mumps. That has never been disputed.  Some years, the vaccine is simply a poor match for the influenzas in circulation. 


But even in a good year, vaccines may only be 70%-90% effective in healthy adults.


The elderly – who need the protection most - seem to mount a far less robust response to the vaccine than do younger adults and children.   Again, hardly a secret.


The response to vaccines among the immunosuppressed – another cohort at greater risk from influenza – may similarly be less than hoped for.  


In fact, as `pro-vaccine’ as I am, I’ve written often about the limitations of vaccines and antivirals.    They are an imperfect solution.


More than a year ago, in Vaccines: Sometimes You Just Need A Bigger Hammer – I wrote.


Over the past couple of years a number of studies have shown that the elderly develop a significantly lower immune response to seasonal vaccinations than do those who are younger.


I've blogged on a number of these studies, including:

Another Study: Flu Vaccines Do Not Reduce Mortality Rates In The Elderly

Study: Flu Vaccines And The Elderly

Flu Shots For The Elderly May Have Limited Benefits

Of the 36,000 flu-related deaths each year in this country, 90% occur in those over 65.    Unfortunately, this is the exact cohort that seems to derive the least benefit from the standard flu shot.


And I’ve lost track of how many times I’ve stated that antivirals don’t cure influenza – at best they can reduce the severity of symptoms.  


Of course, we’ve plenty of anecdotal reports from the field crediting antivirals with salvaging critically ill flu patients. Their value in treating less severe cases of influenza seems in greater doubt.


And just last week, in the NEJM, we got a major review of hospitalized patients with the H1N1 virus, and the conclusion was that antivirals – particularly when administered early – had a positive influence on patient outcomes.


Published at October 8, 2009 (10.1056/NEJMoa0906695)

Hospitalized Patients with 2009 H1N1 Influenza in the United States, April–June 2009

N Engl J Med 2009 0: NEJMoa0906695


“Data suggest that the use of antiviral drugs was beneficial in hospitalized patients, especially when such therapy was initiated early.”


Proof positive?   Not quite.  


But sometimes you have to go with the preponderance of evidence, not `beyond a shadow of a doubt’.   And for now (and this could change), the evidence strongly suggests that antivirals improve survivability among those most severely affected by influenza.


Do I wish we had stronger, more convincing studies?  


Of course I do.  And one of the things that I hope comes out of this pandemic is that we improve the science that we base our policies on. 


The idea that science is neat, clear, and orderly – and that the truth is always immediately obvious – is pretty naive.   Practically every week I get new, conflicting studies about some aspect of influenza science. 


In the past couple of weeks we’ve seen reports suggesting that the seasonal flu shot either A) Increases your susceptibility to getting H1N1   B) Decreases your susceptibility to the pandemic virus   or C) Has no effect either way.

Take your pick.


So I’m not terribly shocked by the conflicting, and sometimes sparse data we have on vaccine and antiviral efficacy. It simply means that there’s a lot of work to be done.


The authors of Do Vaccines Matter?  raise important and legitimate questions, and their piece illustrates why we need more and better research.


While definitive answers regarding the efficacy of vaccines and antivirals remain elusive, the preponderance of evidence  right now suggests that they are both safe and beneficial.   


And since the cohort most likely to be affected by the novel H1N1 virus - those under the age of 65 – generally mount the best immune response to a vaccine, getting the shot seems like pretty sage advice.  



Vaccines and antivirals, in my opinion, are very much like seatbelts in your automobile.  Wearing them may not guarantee your survival in an accident, but they certainly do improve your odds. 


And so it is in a pandemic, where guarantees are in distressingly short supply, that sometimes all you can do are those things that will help improve your odds.  


Even if they aren’t perfect.