Tuesday, December 6, 2011

Vaccinonomics

Warning:  This is one of my wonkier postings.  Read on if you'd like to learn more about the supposed science of economic analysis, and how it shapes healthcare policy.
How much would you pay to keep this little critter away from your child?*

I don't have a compelling personal anecdote about meningitis, and I hope I never do.  Meningococcus is one of the more common causes of meningitis, and this bug gives even hardened doctors and nurses the heebie-jeebies.  For one thing, it spreads by close contact, so members of the same household, or healthcare workers exposed to secretions, must take antibiotics to ward off the same fate.  And if you don't die from meningococcus, you could end up with brain damage or multiple limb amputations, since one of the complications is gangrene.

So we should be thrilled that there's a vaccine against the most common serotypes that cause disease in adolescents and young adults, who are particularly susceptible to this infection.  In the past, a single dose at age 11 or 12 was thought to be protective for 10 years, but recent studies have found that immunity lasts for only five.  Last week, the American Academy of Pediatrics issued a statement recommending a second, booster dose for 16-year-olds.

No one argues that adding a booster won't save lives.  But is it worth the extra cost, given that meningococcus is still a relatively uncommon disease?  Already, kids routinely receive about 30 shots in their childhood -- double the number back in 1980.  An editorial in the New England Journal of Medicine argued that "routine adolescent [meningococcal vaccine] does not provide good value for money, largely because of low disease incidence rates and relatively high vaccine cost."

You might argue that you can't put a price on a human life, but it turns out you can.  Economic analysis is the science of quantifying the cost of healthcare interventions, but as you'll see, there are a lot of smoke and mirrors involved.

Let's start off with the basics.  One way to measure the cost-effectiveness of a vaccine (or a pill, or seatbelts, or virtually anything) is to express it in dollars per life-year saved.  You can see right away that if you had a vaccine that was equally effective across all age groups, it is cheaper to save the life of a baby than the life of a 70-year-old, since you could potentially add 80 years to the baby's life, but only 10 years to Grandpa's.  It doesn't mean the baby's life is worth more, only that the vaccine is a bargain when given in infancy.

Some illnesses rarely cause death, but there may still be value in preventing them, to avoid complications, hospitalizations or lost productivity.  So most economists use the measure of dollars per quality-adjusted life-year, or QALY, saved.  How do economists quantify quality?  Simple: They ask patients, "If 1 is the value of a perfectly healthy life, and 0 is death, how would you rate having this condition?"  Suffering through a cold might be 0.999, while being hooked up to a ventilator and feeding tube might be 0.1.  (There are no negative numbers in quality-of-life estimates, though there are probably some fates worse than death.)  Already, you can see one of the inherent problems with economic analysis -- quality is an extremely subjective measure.

The other methodologic difficulties with this type of research involve knowing what to include in the accounting of costs and benefits, and which estimates to use.  Do you analyze the economics from the individual's standpoint, or society's, or the third-party payer's?  Each analysis is specific to its country; you can't take an analysis from, say, Singapore, and apply it in the U.K.  Although our body of scientific knowledge is constantly changing, economic analyses become rapidly outdated as costs fluctuate.  Econ analysis for vaccines is especially tricky, since you have to take herd immunity into account.  In other words, the benefits of immunization may extend beyond the immunized.


One popular myth is that a "cost-effective" intervention saves money.  In fact, most modern prevention and treatment measures don't save money at all.  The biggest exception?  Almost all routine early childhood immunizations, such as the measles and polio vaccines, save money.  The same isn't true, though, for the newer vaccines targeting tweens and teens.  Why is that?


Well, for one thing, adolescents are a hardy group.  Their immune system is stronger than infants', and when they do die, it's often a result of their own stupidity -- think of texting while driving.  On top of that, there's no loss in productivity when they're sick.  (Insert your own lazy teenager joke here.) An adult takes time off from work for illness, and a parent needs to stay home with a sick toddler, but a jobless16-year-old with the flu can fend for himself.  And then there's the fact that the newer vaccines aimed towards this age group are a lot more expensive than the older ones.  So let's look at the cost-effectiveness of some of these vaccines in the U.S.:


Meningococcus is one of the more expensive, with $88,000 per QALY saved.  Giving the double dose ends up being about the same price, since even though you double the cost, you save more lives.

Annual influenza vaccine in 12- to 17-year olds is very pricey, at $119,000 per QALY.  Compare this to only $11,000 per QALY in 6 to 23-month olds.


Human papillomavirus virus (HPV) wasn't too bad, at $15,000 to $24,000 per QALY, although it's much more expensive to vaccinate boys than girls, since cervical cancer is more common than penile or anal cancer, and reducing HPV in girls should reduce the frequency of screening and treatment of pre-cancerous lesions.

Hepatitis A ranged from cost-saving in college freshmen to $40,000 per QALY in 15-year-olds.  (The wide range should clue you in to the fragility of these economic models.)


The cheapest vaccine?  Pertussis booster, at the bargain basement price of $6,300 per life-year saved.  Outbreaks of pertussis, or whooping cough, have been linked to waning immunity in adolescents and adults, and while whooping cough is not particularly dangerous to older kids, it's very contagious and can kill unimmunized newborns.  Much of its cost-effectiveness derives from herd immunity and the fact that pertussis is an older, cheaper vaccine.  Middle school students in California are now required to get the pertussis booster.


Of course, these numbers give the illusion of hardness to a science that's based on the softest of data.  And what is the definition of a "cost-effective" intervention anyway?  By convention, a maximum limit of $50,000 per QALY saved is considered cost-effective.  There's no logical reason why this number appears in the literature.  It hasn't budged in the past two decades, despite inflation.  And $50,000 may be a year's salary for one family, or the price of a car for another.  But that's the figure in the minds of policy makers when they try to decide whether a new treatment should be covered by insurance.

Here's another way of looking at the numbers:  The NEJM editorial laments that the public-sector cost of immunizing one child until adulthood (not including annual flu vaccines) is about $1,450 for males and $1,800 for females.  I was surprised to see that this number was so low.  After all, we spend much more than that educating and clothing our children.  Heck, $100 a year is less than my caffeine budget.  Shouldn't we be spending at least that much to keep our kids healthy?


*For you microbiologists out there, this is technically gonorrhea -- but it's in the same family of bacteria.  Giant Microbes apparently found there's a bigger market for an STD than for meningitis.

2 comments:

  1. My personal thought on the meningococcal vaccine--as with most vaccines--is that a huge reason why the incidence of the illness is so low is because so many people are vaccinated. With vaccination rates dropping off substantially in many areas--due to voluntary opt out, not to health reasons--and some diseases that we thought were a thing of the past seeing a revival, it makes sense to me to get all of the recommended vaccines...even if they aren't the best bang for your buck.

    Maybe if you home school your 16-year-old, not getting the vaccine makes sense. However, for those who are in schools or who plan to go off to college, it's a really smart thing to do. :) Just my two cents.

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  2. Actually, the incidence of meningococcal meningitis has always been low, hovering around 1 in 100,000 even before the vaccine. Compare this to varicella (chickenpox), in which >90% of the population contracts it, unless immunized. The big difference, of course, is that chickenpox is rarely deadly, while 1 out of 7 adolescents who are infected with meningococcus die, and 1 out of 5 have a permanent disability.

    I agree -- it definitely makes sense for college kids in close quarters to get vaccinated.

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