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A Vaccine's Unintended Consequences

When a new vaccine was approved in 2000, experts hoped it would protect children against a common bacteria that causes a variety of illnesses, including meningitis. They were not disappointed. The vaccine, known as Prevnar, has resulted in a sharp drop in cases. The question was: Would it also reduce cases in adults?

A new study led by Lee Harrison of the University of Pittsburgh says the answer is yes. An analysis of data collected at eight centers around the country between 1998 and 2005 by the federal Centers for Disease Control and Protection found that overall there was a 30 percent drop in pneumococcal meningitis caused by strains of the bacteria Streptococcus pneumoniae.

The study, in today's New England Journal of Medicine, found that, as expected, the biggest drop occurred in children under age 2, among whom cases fell by 64 percent. But there was also a 54 percent drop in cases among the elderly--presumably because the fall in infections among children meant fewer kids were spreading the pathogen to adults.

The news, however, is not all good. At the same time, there was a 60 percent increase in strains of the bacteria not covered by the vaccine. The reduction in those covered by the vaccine probably created a void that the other strains filled, the researchers speculated. Perhaps even more worrisome, there was an increase in the number of cases caused by strains of the bacteria resistant to antibiotics. That's probably because as the other strains became more common and doctors started treating them with antibiotics they developed more resistance.

None of this means that children should not continue to receive the vaccine. Quite the opposite. But it does mean that doctors should be as judicious as possible about using antibiotics to minimize the chances that the antibiotic resistant strains will become more common. The findings give impetus to drug makers to speed the development of new versions of the vaccine to cover more strains. And that work is already underway.

By Rob Stein  |  January 15, 2009; 7:00 AM ET
Categories:  Family Health  
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Are you kidding me? The fact that there has been a 60% increase in OTHER strains of the bacteria not covered by the disease (serotype replacement, I believe is what it is called), and that there is an increase in antibiotic resistant cases is NOT AT ALL a reason to not consider this vaccine? Seriously? The only positive that is given in this article is a 30% decrease in the number of meningitis cases caused by this exact strain of bacteria. Honestly if I'm getting meningitis, I could care less what strain of bacteria it is. If this vaccine is making other types of bacteria cause meningitis even more...then what's the point?

Posted by: DCResident00 | January 15, 2009 9:31 AM | Report abuse

DCResident00 - I'll make it simple: let's say there's 10 "Tom" bacteria and 4 "Paul" bacteria floating around. The vaccine reduced the cases of Tom by 60%, but increased Paul by 60%. So, while the Paul version is harder to treat, we're still net down because there's only 4 Tom now (there's 6 Paul). Plus...getting rid of Tom is still a good thing. So, yes, getting vaccinated is still important.

Posted by: byte1 | January 15, 2009 1:14 PM | Report abuse

Thanks, Byte1, you've encouraged me to look at more facts. Apparently there are over 90 strains of streptococcus pneumoniae. Prevnar protects against 7 of these, and those 7 were responsible for 60-80% of invasive pneumococcal disease in children. Apparently up to 21% of the 90 strains are resistant to 2 or more types of antibiotics. So to use your example, but with real numbers: There are 7 "Tom" bacteria and 83 "Paul" bacteria. So with the vaccine we're reducing the cases caused by the "Tom" bacteria, but increasing the cases caused by the significantly higher number of (and to use your words - "harder to treat") bacteria. Getting rid of Tom is only a good thing if it isn't immediately replaced by the "harder to treat" Paul. Still don't get it. Sorry.

Posted by: DCResident00 | January 15, 2009 2:22 PM | Report abuse

Anyways, Byte - you can't use made up numbers and then use those numbers to prove a point. Let's use your example, except flip the made up numbers - let's say for argument's sake there are 4 Toms but 10 Pauls - by your calculation, the Toms are decreased by 60% and the Pauls are increased by 60%, making waay more Pauls. Convenient that the numbers you made up "prove" your point.

Posted by: DCResident00 | January 15, 2009 2:34 PM | Report abuse

DCResident00: It really depends on the exact numbers. You said that the strains covered by the vaccine are responsible for 60-80% of the disease in children. Let's take first 100 cases at the lowest end, meaning 60 cases are covered and 40 are not. A reduction of 30% in the 60 cases results in 42 cases, and an increase by 60% in 40 cases results in 64 cases being the total number of cases now 106 (a 6% increase), which is not good. On the other hand at the high end of the coverage range 100 cases have 80 covered and 20 not covered. A reduction of 30% of the 80 covered cases yields 56 cases and an increase of 60% of the 20 not covered cases yields 32 cases for a total of 88 cases (a 12% decrease) which is now good. But among children 2 years old or less, the reduction of cases is 64%, not 30%, so the vaccine is clearly a much better option for this more vulnerable population.

Posted by: ogs123 | January 15, 2009 3:47 PM | Report abuse

Thanks, ogs - but I'm still concerned about the higher incidence of bacteria that is resistant to the drugs we have. Is there type of thing where all this superbug and MRSA type stuff is coming from?

Posted by: DCResident00 | January 16, 2009 10:04 AM | Report abuse

While things like the irresponsible use of antibiotics (physicians prescribing them for viral infections just to make the patient happy and patients not finishing their entire course of antibiotics once they start to feel better) the major source of antibiotic resistance comes from factory farms where animals are given constant low level doses of antibiotics. This creates the perfect breeding ground for antibiotic resistance and if anyone is actually worried about things like superbugs and MRSA he or she would only eat antibiotic free milk, eggs, and meat (you don't have to spring for organic, just look for antibiotic free). Our quest for the cheapest meat possible is going to create a public health crisis in this country.

Posted by: ftg_somerville | January 18, 2009 1:15 PM | Report abuse


Agree totally! Organic or just antibiotic-free meat is the way to go. Or for the best option, no meat at all.

Posted by: jaxom | January 19, 2009 8:19 PM | Report abuse

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