(10 pm. – promoted by ek hornbeck)
Human Papilloma Virus (HPV) is one of the most common viral infections in the population. HPV causes nuisance conditions such as common warts up to deadly cancers. Some estimates indicate that essentially all cervical cancers are caused by various strains of HPV.
There are very many strains of HPV, most all of them highly contagious. Let us spend a few moments discussing this important group of infectious agents. Before we get started, let me make it clear that this discussion will be frank and might seem to be extremely graphic to some. That is just the way it is, and to water down the content would not do a service to anyone.
First of all, an apology. Popular Culture did not appear Friday evening due to my own laziness. I was 90% into it when I hit some odd combination of keys (which I have not been able to reproduce experimentally) that wiped out everything after the introduction. It was 8:40 PM at the time, so there was no way to recover from that. Now I use the Save and Preview button after each paragraph (if site administration is reading, returning to the old Autosave feature would be wonderful), and I have installed the Lazarus software that is supposed to mirror all entries. Now, to HPV.
There are scores of HPV types, most of them harmless or at worst nuisances. For example, common warts are caused by Types 2 and 7 and often resolve on their own, although highly established infections often must be frozen off by a dermatologist. There are some over the counter remedies, most of which contain salicylic acid. They work somewhat, and the newer ones that use liquid carbon dioxide probably are as effective as the liquid nitrogen treatment.
A more serious kind of wart is the plantar wart, which mainly occurs on the soles of the feet, caused by Types 1, 2, 4, and 63. These warts, unlike common warts, tend to grow into the skin rather than out from the skin, and can cause real problems walking for those afflicted with them. Likely it is from pressure exerted on them that makes them grow inwards. Salicylic acid treatment seems to the most effective treatment.
Genital and oral warts are also caused by HPV, and with the almost universal acceptance of oral sexual activities has caused the oral ones to increase in frequency dramatically over the past few decades. Types 6, 7, and 11 are responsible for many of these. They also can infect the anus. The front line treatment for the genital and anal ones is podophyllotoxin, an extract of the American Mayapple plant. Interestingly, that plant also produces delicious fruit, if you can beat the deer and the rodents to them in the early summer.
However, there are several strains that are quite hazardous. Types 16 and 18 are of particular concern, and 31 and 45 are also quite dangerous, but much less common than 16 and 18. Over 70% of all cervical cancer is caused by either Type 16 or 18, or a combination of them. Interestingly, Type 16 is also isolable from many oral and throat cancers, and as tobacco use declines in the developed world is projected to become the major cause of oral and throat cancers.
Traditionally, monitoring of women of childbearing age (this presumes sexual activity) on a regular basis with Pap smears has been the first line of defense against cervical cancer. If abnormal cells are found, several treatments are available, including treatment with liquid nitrogen. If actual cancer develops, surgical intervention along with chemotherapy and radiation is normally the treatment course. Prognosis is excellent when caught very early, but as it progresses the prognosis becomes increasingly worse, like that for most other cancers.
Doc, you may ask, is it possible to develop a vaccine for these highly dangerous types of HPV? The answer is yes, to a point. There are currently two vaccines approved, and we shall talk more about them later. Part of the problem was to come up with virus like particles that resemble the actual virus closely enough to produce a strong immune response but not cause infection themselves. Until recently this had not been achieved, but is now done on a regular basis.
Another problem with the vaccine is that it must be given to people before they have been exposed to the types of HPV for which the vaccine protects. For these serious cervical cancer (I should mention that rectal and penile cancers are often caused by the same HPV types) risks, that means vaccination at a very early age, perhaps around ten years. Here is where the controversy begins.
There is a significant minority that believes that vaccination against HPV is immoral. The “logic” goes thusly: if my child is sexually pure and marries a virgin, then there is no possibility for infection. I kid you not! Some people, such as the revolting Tony Perkins of the Family “Research” Council advocate exactly this position. He has gone so far as to say that he will no allow his children to be vaccinated.
I should remind ole Tony that Type 16 is known to be transmitted by kissing, albeit rather intense kissing, betwixt an infected and an uninfected person. Once oral infection is established, it is quite possible to self inoculate to other regions by any number of activities.
Let us look at some statistics. This study was published in Journal of the American Medical Association in 2007. For the age group betwixt 14 and 19 years, 24.5% of the US population is infected with some type of genital HPV. Obviously vaccinating people at 14 years or older will not protect almost one quarter of the population. I should point out that this study includes many types of HPV, not just the high risk ones. At 20 to 24 years, the rate of infection jumps to 44.8%, almost HALF of the population. This study only considered active infections, not people who were previously infected and no longer carry the virus.
Look at it this way: say you are 17 and in high school (and uninfected). Since HPV has a nearly unit probability for transmission, you have just about a 1 in four chance of contracting HPV by having sex (condoms are of only limited protection because the virus exists on the skin and mucous membranes and not just in seminal fluid). If you have two partners, you have almost a 50% chance of contracting HPV.
Now, say you are 21 and in college. Because of the environmental differences betwixt high school and college, you are much more likely to be sexually active, AND your chances of becoming infected are now almost 1 in 2, with a single partner. But wait! Just because your partner in not infected today, what about next week? What if you have more than one partner? Some estimates indicate that a college student, with a single partner each year for four years, almost 85% of uninfected people will become infected. One sexual partner per year is pretty conservative in my opinion.
Then there is the question about whether both boys and girls, rather than just girls, should be vaccinated. One school of thought holds that since females are more likely to develop life threatening conditions (cervical cancer is by far more common than HPV mediated oral and anal cancers) that it is more cost effective to vaccinate girls only. The other school of thought, to which I personally subscribe, it that if both populations are vaccinated then transmission from vaccinated males to unvaccinated females will be reduced, and the collateral benefit results that anal and oral cancer rates will be reduced in both populations.
Just as an aside, only in 1972 was it even postulated that HPV might be associated with any type of cancer, and only since 1976 that postulated that HPV might be involved with cervical cancer, and only since 1983 that HPV was positively identified in cervical cancer. This is still very new science.
As another aside, my mum’s closest friend died of cervical cancer at around the age of 50, I am guessing. At the time, surgery, some chemotherapy, and radiation was all that there was. As far as I can tell, the liquid nitrogen treatment for destroying precancerous cells had yet to be developed, but I could be incorrect about that. Any oncologists out there are asked to clarify this statement, and any others in this piece as well.
Currently, there are two vaccines approved and on the market. Cervarix, by GlaxoSmithKline, protects against HPV Types 16 and 18, whislt Gardisil, by Merck and Company, in addition to these two types also is protective against Types 6 and 11 as well. Types 16 and 18 are the two worst agents that cause cervical cancer, whilst Types 6 and 11 cause non lifethreatening but still very bad genital warts. Remember, Type 16 is also implicated in penile, anal, and throat cancers as well.
Cervarix also seems to have some effectiveness against Types 31 and 45, the other two highly dangerous types of HPV for cervical cancer. Whether that is because those types are serologically similar enough to Types 16 and 18 is not known for sure to me. I have not found any data about Type 31 and 45 efficacy for Gardasil, but if the hypothesis that I made just before is correct, it should be similar to Cervarix. There are always concerns about the safety of any vaccine, and both of these seem to be quite safe, although fainting is seen more often than with other vaccines, but I sort of suspect that this has to do with psychology.
Muscle soreness and fever also seem to be a bit higher than with other vaccines, and the manufacturers tell us that is the result of the virus like particles mimicking a real infection, although there is not any infection. Neither of these vaccines contain any actual virus, either attenuated (live) or deactivated (killed). Neither contains any mercury preservative, such as thimerosol, which are mistakenly associated with the onset of autism. Even if there were a link to mercury containing preservatives and autism, the point would be moot since the central nervous system is well developed by the age of 9 or 10.
Now we have to look at economics. The three injection regimen of Gardisil costs $360, give of take. That is really a fairly expensive vaccine. You can buy a flu shot (for what it is worth) for $25 at many big box stores. Since there are only around 3900 deaths occur from cervical cancer in the United States in any given year, that does work out very well. However, the cost of treating the 11,000 cases that are found every year is considerable. And there is another factor: Gardisil (not Cervarix) also prevents around 90% of genital wart infections, and genital warts are very common and not without cost to treat.
I shall close with my personal views. My children (all boys, now young men) are far beyond the age where these vaccinations would do much good, so they are moot in relation to this discussion. However, if I had a nine or ten year old, regardless of sex, I would find a way to buy the vaccinations for them. This would protect them from either contracting (or infecting someone who could contract) over 70% of the cervical cancers. In addition, it would protect them from many throat cancers, or for passing them to intimate partners in later life. This is not to mention penile and rectal cancers. I am a realist. If I had a 10 year old, I would just assume that he or she his a high likelihood of becoming sexually active within five years. That may sound rash, but look at the statistics that I quoted for the 14 to 19 age group. I personally believe that it a moral and medical no brainer to vaccinate against these common and, potentially deadly, viruses.
One last thought. Since both vaccines are really effective against cancer causing Types 16 and 18, it is still important for all women who are sexually active, or have been, to have regular Pap smears, since 30% of cervical cancers are caused by other types. I would indeed be foolish to have a false sense of security just because one is protected against only 70% of the threat. If you do discover a sore in your mouth, it’s a good idea to have your doctor take a look at it. Some more information about that can be found here.
Please let me know you thoughts on this controversial subject. Science is supposed to be controversial.
Well, you have done it again! You have wasted many einsteins of perfectly good photons reading this infectious piece. And even though the Tea Party types admit it to themselves that THEY were the cause of the downrating of our bonds when they read me say it, I always learn much more than I could possibly hope to teach by writing this series, so keep those questions, comments, corrections, and other feedback coming. Tips and recs are also welcome. I shall hang around this evening as long as comments warrant, and shall return tomorrow evening around 9:00 Eastern for Review Time.
Doc, aka Dr. David W. Smith