Field of Science

"Recontrolling pertussis": a phrase we shouldn't have to hear

The word is going out that a lot of people need to get a pertussis booster shot Pertussis, more commonly known as whooping cough, is a bacterial infection that is very dangerous and sometimes fatal in young infants, whose immune systems are too immature to protect them. The only way to protect the very young is to make sure those around them -- parents, siblings, other relatives, and day care providers -- are vaccinated. Many adults were vaccinated as children, but the vaccine's protection wanes after about ten years, so they still need a booster shot if they are caring for children.


What's new here? First, there's a new report from an expert advisory panel to the Centers for Disease Control. The CDC panel is urging doctors to vaccinate everyone who might be in contact with young children, even if they can't remember when or if they had the pertussis vaccine. A report in the Journal of the American Medical Association this past week quotes pertussis expert Michael Brady, M.D., who chairs the American Academy of Pediatrics committee on infectious diseases, who says the new recommendations are needed as part of our efforts at "recontrolling pertussis."


What does Dr. Brady mean when he says "recontrolling"? Well, whooping cough is not under control right now. In California, a serious epidemic continues. (See my previous post about it here.) The CDC reports over 7,800 cases of pertussis throughout California, including the deaths of 10 infants. These infants were too young to be vaccinated, and their deaths are a tragedy that could have been prevented. The last time we saw this many cases of whooping cough in California was 63 years ago, in 1947.


Meanwhile, Michigan continues to have its own pertussis outbreak, with 1,092 cases this year, and 902 cases last year. And the pertussis epidemic has spread to Ohio, where two counties collectively report 910 cases this year, the largest number in 25 years.


In infants and very young children, pertussis causes violent, spasmodic coughing that repeats over and over. The cough is so strong that babies cannot breath properly, and after multiple coughs they will breathe in sharply with a classic "whooping" sound, which gives the disease its name. Pertussis is far more dangerous in infants than in adults: from 2000-2004, 92% of the pertussis deaths in the U.S. were in children less than one year old.


Whooping cough used to be under control. The number of nationwide cases was dropping for years, and although the disease didn't disappear, we were getting to the point where most people didn't know anyone who'd had it. The question is, why did we lose control? Is a new strain of pertussis to blame? Or is it our own behavior?


Unfortunately, the answer seems to be that these outbreaks are spreading as a result of falling vaccine rates, for which we can thank the anti-vaccine movement, which has been very effective at getting their message out through mainsteam media, including the Larry King show, Oprah, and The Huffington Post. One of the main groups in this movement is the mis-named National Vaccine Information Center, which really should be called the Vaccine Misinformation Center. Their pertussis web page contains a section titled "Can pertussis vaccine cause brain damage and death?" The mere act of asking this question is part of their anti-vaccine strategy. And rather than answering "no," the website goes on for several paragraphs, selectively quoting from studies that looked at vaccine risks - which are very small, but not zero - while ignoring the much greater risks of the disease itself. NVIC's website concludes by claiming (without citation) that

"Most pediatric neurologists acknowledge that vaccination, including use of vaccines for smallpox, rabies, influenza, mumps, measles, tetanus, polio and pertussis, can and does occasionally cause neurological complications that can lead to permanent brain dysfunction."

Scare tactics indeed. Not only is NVIC trying to scare parents away from the pertussis vaccine, but they take the opportunity to warn against many other vaccines. NVIC claims on its website that it "does not promote the use of vaccines and does not advise against the use of vaccines," but that, to put it bluntly, is a lie. Their primary mission is anti-vaccine advocacy, as illustrated by their current advertising campaign that claims we are "over-vaccinating" children and injecting them with harmful toxins.


So we can thank NVIC and other anti-vaccine groups, such as Generation Rescue (which claims, among many other mistaken notions, that the pertussis vaccine causes autism), for the re-emergence of whooping cough.


In contrast, here's what the CDC says about the pertussis vaccine:

"Results from clinical trials showed that these vaccines are very safe for infants and children....The most common adverse events reported have been tenderness and redness where the shot was given, headache, diarrhea, and fussiness."
Unlike NVIC, the CDC gives details and citations to the scientific literature. The CDC also maintains a separate page listing all possible side effects from a long list of vaccines.

The current vaccine against whooping cough is called DTaP or TDaP (short for " tetanus toxoid, reduced diphtheria toxoid and acellular pertussis", and the evidence shows that it is very safe. The vaccine does not contain any whole cell, not even killed bacteria, meaning that it is impossible for the vaccine to cause even a mild case of any of the diseases that it protects against.


The CDC advisory on the pertussis vaccine is not part of a conspiracy to "over-vaccinate" the public, or to pad the profits of Big Pharma. (By the way, to pre-empt some of the commenters: I am not paid a single penny by any pharmaceutical company, nor am I paid by Forbes.) The advisory is a necessary step to "recontrol" whooping cough, a disease that we should not have let back into our communities. I fear that if we keep listening to the anti-vaccine activists, pertussis will be just the first in a series of diseases that will return to plague us, causing needless suffering and anguish.

Short and sweet: the strawberry genome

Happy holidays to everyone, and here's a very short seasonal post: the strawberry genome is here! Kevin Folta from the University of Florida led the effort to put the paper together for the journal Nature Genetics, and he has a nice behind-the-scenes summary on his blog here. One tasty tidbit is that the initial proposal for funding failed because the peach and apple genomes had stronger support - but strawberry beat them both (neither of those genomes is yet complete). It's the first plant to be assembled entirely from next-generation sequences, thanks in large part to the efforts of assembly guru Art Delcher.

And the genome really is "short and sweet", weighing in at just 240 million bases of DNA. (See the paper here.) That's pretty small, for a plant. The apple tree genome is over ten times larger, and the pine tree is 100 times larger. But strawberries are sweeter.

Non-GMO foods: nonsense

I was at a local organic food market recently buying lunch, and I noticed that my avocado-and-hummus sandwich proclaimed that it contained "non-GMO" ingredients (GMO = "genetically modified organism).

Now, I happen to like organic groceries. The ones near me tend to have better produce and fish, two of the main ingredients in my diet. But organic markets are a hotbed of bogus, even laughable health claims, and I often have to suppress my urge to complain to the store's management. (I once wrote to Whole Foods, but they never responded.)

Here in the U.S., most of our food supply is filled with so-called GMO foods, but in Europe the situation is dramatically different. For some reasons, our otherwise well-educated European friends are terrified of GMO foods. They don't seem to realize that we've been modifying the genes in our foods for centuries, and it's generally been a good thing. The latest biotechnology merely allows us to modify plants (and animals too, though none are yet on the market) much more quickly, and more intelligently. Today we can alter just a few genes to produce a more-desirable plant, rather than doing it by trial-and-error over many generations.

In fact, the "GMO" foods of the past likely had hundreds of unknown gene modifications.Farmers selected plants for seed because they looked and tasted good, without having any idea of what was really different about them.

Let's take a look at corn. The corn we eat today, organic or not, looks nothing like the "real" corn (or maize) from centuries ago. The earliest corn cobs discovered by archaeologists were tiny, with only a few kernels. This picture shows a primitive form of corn, called teosinte, compared to modern corn:

The history of corn is a history of genetic modifications made by earlier humans who didn't even know what a gene was. Today's GMO food is simply a continuation of that history.

That hasn't stopped opponents of GMO foods from sounding the alarm. Even the World Health Organization makes some errors on its website, where it discusses three main "issues of concern for human health":

  1. Allergenicity. Not a problem. The WHO says "No allergic effects have been found relative to GM foods currently on the market."
  2. Gene transfer. The WHO gets this one wrong. They write that "gene transfer from GM foods to cells of the body or to bacteria in the gastrointestinal tract would cause concern if the transferred genetic material adversely affects human health." Gene transfer is a topic that I've studied in some detail, and published papers on. The WHO says that the likelihood of a gene transfer event is "low," but in fact it is vanishingly small - so small, in fact, that not a single gene transfer event has ever happened. In the history of our species, and of all mammals, going back tens of millions of years, not a single gene from something we've eaten has been transferred into the human genome or, as far as we can tell, into bacteria within our guts.
  3. Outcrossing. This is "the movement of genes from GM plants into conventional crops," and this really can happen - they're the same species, so they can interbreed. But it's only a concern if GM plants are harmful, which they're not.

The bottom line is, you're far more likely to be harmed by being hit on the head by a corn cob than by some kind of deviant GMO corn gene.

The WHO concludes that GM foods "are not likely to present risks for human health." Of course, not all GMO foods are good. I'm not a fan of engineering crops to be more tolerant of pesticides, for example: this type of GMO food benefits big agricultural firms rather than the consumer. And it is theoretically possible to insert harmful genes into plants, but agricultural firms wouldn't have any reason to do that.

So the next time you see the non-GMO claim in your grocery, ask yourself whether the ingredients could really be completely unmodified from their "natural" state. I doubt it.

My sandwich was really good, by the way.