The good news and bad news about Prevnar, Wyeth’s anti-pneumococcal vaccine, may have worrisome implications for Gardasil. Like Gardasil, Prevnar (PCV7) only targets a few selected strains of the pathogen it seeks to vanquish.
The very good news is that since it was adopted as a routine childhood vaccine, rates of a deadly form of meningitis have fallen by 30 percent in children and adults. Because kids no longer pass the disease on to the adults they’re in contact with, they confer a sort of “herd immunity” on those adults.
The bad news is that a team of researchers led by Dr. Lee Harrison of the University of the Pittsburgh School of Medicine found that by 2005 non-PCV7 strains of meningitis had increased by 60.5%. And worse news: the percentage of strains not sensitive to penicillin rose from 19.4 percent in 2003 to 30.1 percent in 2005.
When only selected strains of a pathogen are targeted, a vaccine can create a “replacement disease” as non-targeted strains fill the void and fulfil the principle that “Nature abhors a vacuum.”
Critics of Gardasil have long been concerned that this could happen with the new vaccine, which targets only four of many strains of HPV.
Wyeth, meanwhile, is testing a new version of Prevnar that will cover an additional 13 strains of pneumococcal bacteria. Harrison believes that the new vaccine, if approved, should take care of about half of the disease that remains.
Harrison’s study can be found in the New England Journal of Medicine.
If you are considering having the Gardasil vaccinations, or have already had them, do you think replacement disease is a concern as well as side-effects that may be unknown or under-reported?