More evidence for the effectiveness of vaccines

Yesterday, I wrote about how two anti-vaccine activists, Barbara Loe Fisher and Joe Mercola, were unhappy that bloggers targeted their advertisement that they put on the CBS Times Square JumboTron for a letter-writing campaign to try to persuade CBS Outdoors to do the right thing and stop selling ad time to groups who promote a philosophy that is a threat to public health. Thats why I have to love it when by coincidence a paper is released that provides yet one more example of the benefits of vaccination. In this case, it even deals with one of the “lesser” vaccines. Well, it’s not really a “lesser” vaccine, but it the frequent victim of jeers and sneers from the anti-vaccine set, who proclaim it as unnecessary. Some of them even go so far as to have “parties” for their children to infect each other with the disease.

Yes, I’m talking chickenpox, otherwise known as varicella.

If you peruse the anti-vaccine blogosphere, as I do on a regular basis, it won’t take you long to find extended rants against the varicella vaccine, proclaiming it as unnecessary, harmful, or at best useless because chickenpox is supposedly a mild childhood disease that causes no harm. Of course, pediatricians know that that’s not true. Before the vaccine, approximately 4 million people developed chickenpox, with around 150,000 cases of complicated disease and around 14,000 hospitalized per year resulting in around 100 deaths per year. After the vaccine, well, here’s an article hot off the presses in the journal Pediatrics from researchers at the National Center for Immunization and Respiratory Diseases and the Centers for Disease Control and Prevention. I think the title says it all: Near Elimination of Varicella Deaths in the US After Implementation of the Vaccination Program.

The design of the study was simple. The investigators examined national data on deaths for which varicella was listed as either an underlying or contributing cause using the Mortality Multiple Cause-of-Death records from the U.S. National Center for Health Statistics, calculating the age-adjusted and age-specific mortality rates for the years 2002 to 2007, examining trends since the prevaccine years:

Because the number of deaths for 2002-2007 was low, age-specific mortality rates are reported for age-groups younger than 20 years, 20 to 49 years, younger than 50 years, and 50 years or older. We reanalyzed varicella deaths reported during 1990 -2001 according to these age groups. Age-adjusted mortality rates were standardized to the 2000 census population to account for changes in the age distribution of the population over time. In the rate analysis of the new data, we grouped the years into 2 periods, 2002-2004 and 2005-2007. We considered 1990 -1994 as representative of the prevaccine years.

So what were the results? This is yet another time when a picture is worth the proverbial thousand words (and I do think that the graphs I’m about to show shave about a thousand words or so each off of this post, for which those not fond of some of my more logorrheic tendencies will be grateful). The year the varicella vaccine was introduced was 1995, and this is the result:

i-368c12f3e9bcb964f04430c6839b70f8-figure1-thumb-130x83-67726.jpg

(Click to embiggen)

This decline, which was an 88% decline in mortality overall for the entire population, was noted in all age groups over the twelve year period of the study. Indeed, it was most impressive among children and adolescents under 20 years there was a 97% reduction in death due to varicella and a 96% reduction in deaths in people under age 50 overall. In people over 50, the decrease in mortality rates was less impressive but still substantial. After a peak in the mid-1990s, mortality due to varicella fell 67% in people over 50.

It should also be noted that this period encompassed the time when only one dose of varicella vaccine was recommended. In 2006, the recommendation was made for a second dose of vaccine, and we don’t yet have the data for that cohort. The results of this study were so impressive that they led the investigators to write in the discussion:

Our findings invite speculation regarding whether in the future varicella related deaths in the US could be eliminated or reduced to extremely low numbers, similar to several other vaccine-preventable diseases (eg, measles, polio). It is clear that the 1-dose varicella vaccination program with the high coverage achieved had a major impact on varicella deaths.

One weakness of this study is that it didn’t include incidence data. However, we know from numerous other sources that the incidence of varicella fell dramatically after the introduction of the vaccine, for instance, this source and this source, the latter of which cites the vaccine as decreasing varicella incidence by 90%, hospitalizations by 88%, and deaths by 74%. In other words, this study is not the only study showing this result. There are now a number of studies attesting to the efficacy of the varicella vaccine at preventing both chickenpox and complications and death from varicella infection.

It is a frequent tactic by anti-vaccine groups to target vaccines against illnesses that they view as “not so bad.” Chickenpox is viewed by many anti-vaccine advocates as being benign. In most children, it is not that serious, but it does have the potential to cause serious disability and death, which can almost completely prevented using the vaccine. In actuality, it is the anti-vaccine propagandists who are callous in this regard, as they will dismiss the saving of close to 100 children a year as being such a small number as to be “insignificant” or “not worth it,” ignoring the thousands of complicated cases there were every year before the vaccine. They also ignore the suffering children and adults with the disease endure. One of the few things I remember vividly from my childhood is just how uncomfortable and itchy I was when I got the chickenpox. The incessant itching is really hard for a child to endure. Anti-vaccine advocates dismiss all that; some of them even consider it healthy to give their children “natural immunity” to chickenpox by taking them to so-called “pox parties.” It’s a false dichotomy, of course. The immunity provided by vaccination is every bit as “natural” as immunity due to having endured the disease.

Unfortunately, if there’s one thing I’ve learned over the years, it’s that anti-vaccinationists will not be swayed by evidence, data, science, or reason. The evidence for the safety and efficacy of vaccines is overwhelming, as is the evidence that vaccines are not associated with autism, making it incredibly unlikely that vaccination represents a cause of the “autism epidemic.” Vaccines like the varicella vaccine are attacked not because they’re ineffective, but rather because the diseases they prevent are not viewed by lay people as being as serious as other common vaccine-preventable diseases, such as pertussis or measles, but that’s just a smokescreen. After all, pertussis is clearly serious, a potentially deadly disease that can kill; yet anti-vaccine activists are somehow able to downplay its seriousness as well. That’s because, no matter how much it is denied, it’s always all about the vaccines. It always has been, and, I fear, always will be.