Sunday, December 14, 2014

Mumps and the NHL: Don't blame the vaccine

Sidney Crosby has mumps. He joins a handful of other NHL players to be diagnosed over the past several weeks. According to the Pens medical team, Crosby received a booster shot before the Sochi Olympics last year. So what gives? Already, media types have taken to blaming the vaccine. Here's Trib beat writer Josh Yohe:

And here's Shelly Anderson saying something similar:
So, why are players who have been vaccinated coming down with mumps? It's not the vaccine. The CDC estimates that the two dose mumps vaccine is 88% effective. So if 100 vaccinated individuals are exposed to mumps, we'd expect that around 12 of them would still get mumps. And if, say about 25 vaccinated players from an NHL team were exposed, it's not unreasonable for 2-3 of those players to contract mumps. So if 12% of vaccinated people aren't protected, why are the mumps still pretty rare? It's because of herd immunity. Herd immunity is the concept that if most of us are protected from a disease, we can also protect those for whom the vaccines may be ineffective. We can also protect infants and individuals who cannot receive the vaccine. If we can vaccinate most of the population, the disease cannot spread as much, and it's less likely that people who aren't protected even come into contact with the disease. 

Recently, however, vaccination rates have dropped, and the dropping rates have been concentrated in certain areas. Wealthy parents in southern California, for example, have been opting out of vaccinating their children at alarming rates. This puts children and the greater community at risk of contracting and spreading very preventable diseases. There were 438 recorded cases of mumps in 2013, and 1,078 cases from Jan-Nov of 2014. That's almost 2.5 times as many cases, and we've still got a month to go! Also, if anyone has doubts regarding the efficacy of the vaccine, there were approximately 186,000 cases per year before large scale vaccinations began in 1967. Implementation led to a 99% decrease in mumps cases.

It's no coincidence that I mention the plummeting vaccination rates in southern California. The NHL mumps outbreak is believed to have originated with three players from the Anaheim Ducks: Corey Perry, Francois Beauchemin, and Clayton Stoner. These are wealthy guys who play hockey in southern California. This is total speculation on my part, but it's possible these guys came into contact with the disease in under-vaccinated communities. In any case, it's not the vaccine that's at fault, it's the plummeting vaccination rate that has threatened our herd immunity and made everyone more susceptible to contracting preventable diseases.

Update: There were suspected mumps cases from both the Minnesota Wild and St. Louis Blues before the Ducks' cases, but it's suspected that the visiting locker room in Anaheim was the breeding ground. Also, check out this great piece on Deadspin. McCarthy focuses on the waning effectiveness of the vaccine as one gets older, which probably lowers that 88% effective rate for people who were immunized as children but did not receive boosters as adults. 

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