Hi Joann,
[CDC / Markowitz 2013 found that]
Girls who got Gardasil had higher HPV infection rates, but it is
not clear whether Gardasil "increases cancer incidence," for two
reasons.
Reason #1 is that correlation does not necessarily imply
causation:
Reason #2 is that it is not clear whether or not the higher HPV
infection rates will actually result in higher cancer incidence
(more about that below).
Also, I don't know whether girls who get the vaccine after
they are are already infected are more or less likely to get
cancer. I don't know whether that question has been studied. If you
find any studies, I'd be grateful for the information. I do know
that Gardasil is not recommended for older women, which suggests
that it hasn't been shown to reduce cancer incidence in women who
are already infected.
It is not known whether girls who get the vaccine
are more likely to get cancer than girls who don't get the
vaccine. That might or might not be true. In the CDC/Markwitz
study, girls who got the Gardasil vaccine were substantially
more likely to become infected with HPV strains than were
girls who didn't get the vaccine. That's presumably due to
behavior differences: the girls who got the vaccine were more
promiscuous than were the girls who didn't get the vaccine.
The question of causality is harder to answer, though.
Correlation doesn't necessarily imply causation, and even if the
relationship is causal, it might be causal in the other
direction. There are several possibilities.
It could be that girls who got the vaccine were more promiscuous
because they felt safer, because they got the vaccine; in that
case, the vaccine indirectly caused their higher infection
rates.
But that is not necessarily the case. The causality could go in
the opposite direction. I.e., it could be that promiscuous girls
were more likely to get the vaccine because they knew they needed
the protection, due to their promiscuity. In that case, the
vaccine did not cause their higher infection rates.
Or there there might not be any causal relationship at all. It
could simply be that there's some demographic commonality between
promiscuity and likelihood of getting the vaccine, such as
liberal parents, family income level, type of college, religion,
etc. E.g., maybe Unitarians and Jews are both more promiscuous
and more likely to vaccinate than Baptists and Muslims. In that
case, the vaccine did not cause their higher infection
rates.
The girls who got the vaccine were, as expected, much less
likely to be infected with Type 16 or Type 18 HPV. But they were
more likely to be infected with other high risk strains of
HPV, so much so that they were at slightly higher risk, compared
to unvaccinated girls, of being infected with high risk HPV
strains.
That might mean that girls who got the vaccine are at
higher risk for cervical cancer than girls who didn't. But
not necessarily. There is some evidence that HPV
types 16, 18 & 45 might have higher oncogenicity than some of
the other high-risk types, because in women infected with those
HPV strains cervical cancer seems to develop at a somewhat
younger age. So it is possible that, even though girls who got
the vaccine had higher infection rates with "high-risk" HPV
strains, they still might not be at higher risk of cervical
cancer.
No one really knows. But what is very clear is that Merck's claim
that Gardasil will prevent 75% of cervical cancers is utter
nonsense. It might reduce the incidence of cervical cancers,
slightly. Or it might increase the incidence of cervical
cancers, slightly. But it certainly will not
prevent 75% of cervical cancers.
Anyhow, here is the CDC / Markowitz 2013 paper, along with the
supplemental files. Note Table 3, especially:
http://tinyurl.com/markowitz2013.
BTW, the shingles vaccine is another dubious one.
My doc says it's better to skip the vaccine, and instead get
medical treatment quickly if you ever show symptoms of
shingles. He says the shingles vaccine is very expensive, and
only marginally effective, and has a lot of side-effect issues.
He also says shingles is easily & effectively &
inexpensively treated if caught early. Untreated, shingles is a
horrid, painful disease. But if caught early, it can be
effectively treated with [relatively] inexpensive antiviral drugs.
Your brother in Christ,
Dave
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