The more you get involved with science, especially when it comes to matters of health, the more you realize how hard it is to 鈥渒now鈥� anything. Basically we end up making educated guesses based on the evidence that has been accumulated. But the evidence rarely turns out to be white or black, it comes in various shades of gray. The reason for these philosophical musings is a quandry that many parents with teenage daughters are facing these days. Should the girls be vaccinated against HPV, the human papillomavirus? This sexually transmitted virus can cause irregular cell multiplication in the cervix which in turn can develop into cervical cancer several decades down the road. Gardasil, a vaccine that offers protection against some forms of the virus was introduced by Merck in 2006 after being tested on about six thousand women aged nine to twenty six. The trial was actually stopped early because it became apparent that the women given the three injections of vaccine over six months, as the current protocol suggests, developed significantly fewer precancerous lesions than a control group of six thousand women. Results were so encouraging that it was deemed unethical not to inform the women in the control group of the results and give them the choice of being vaccinated.
Although cervical cancer receives a great deal of publicity, it is relatively rare. Roughly 1100 cases are diagnosed a year in Canada and 400 or so women die of the disease. But the important point is that many cases of cervical cancer can be prevented. Pap smears can reveal a problem at an early treatable stage, as has been evidenced by a significant decline in cases since the technique was introduced. But of course it is preferable to prevent infection in the first place, which is what Gardasil can do. However, not without some issues being raised.
While it is true that almost all cases of cervical cancer are caused by the human papilloma virus, Gardasil will prevent only about 70% of cases. Why? Because there are as many as thirty variations of the virus and the vaccine only protects against four types. Two of these are linked to cancer, and two to genital warts. And so far, there is actually no evidence that Gardasil prevents cervical cancer, all we know is that it prevents precancerous lesions. We will have to wait twenty to thirty years before we know whether or not the number of cases decline. It is a pretty good guess though that they will. But at what cost? Any decision about being vaccinated or not comes down to a risk-benefit analysis. Allergic reactions to the vaccine, particularly among women who have yeast allergies, are possible. Acquiring an infection from the vaccine is not possible as it contains no live virus that can multiply in the body. The active component is a protein normally produced by the virus that can trigger the formation of antibodies. Should a subsequent exposure to live virus occur, these antibodies can prevent the virus from getting a foothold and multiplying. Of course, there is no chance for absolute protection, so Gardasil is certainly no substitute for regular Pap smears.
While the vaccine cannot cause an HPV infection, pain and redness at the injection site can occur, and headaches, fever, nausea, dizziness and fainting have been noted after a jab. There have also been anecdotal reports of blood clots and neurogical diseases such as Guillan Barre Syndrome and Amyotropic Lateral Scleroisis being triggered by Gardasil. The evidence for any cause and effect relationship here though is very weak. When you have millions of women receiving the vaccine, some of course will develop various health problems after being vaccinated, but not as a result of being vaccinated. The question is whether or not the incidence of such diseases is greater among those who have been vaccinated than among girls and women who have not. So far, epidemiological evidence does not show a link. Then of course Gardasil also raises some ethical questions. Does it encourage precocious sexual activity by removing some of the fear of acquiring a sexually transmitted disease?
If the vaccine is to be used, the current opinion is that it should be administered before sexual activity has begun. However, it can still be useful later, because even if exposure to the virus has occurred, it may not have been to all four varieties against which Gardasil is effective. How long the antibody protection lasts is not known, since studies have not exceeded five years. It is possible that booster shots may be necessary. Whether or not middle aged women can benefit from the vaccine is also an open question, but some physicians offer the vaccine to women in their thirties and forties who re-enter the dating scene. There is also some evidence that Gardasil can prevent HPV infection in men, which is of particular interest in the gay community because of a known link between the HPV virus and anal cancer. The vaccine , however, is not commonly used in men and is targeted only to women in the nine to twenty six age range. Although the vaccine is expensive, projections suggest that it is cost-effective. The savings in cancer treatment should more than offset the cost. Given that no surprising side effects are encountered. And on that, all we can do is make an educated guess. There are no hard facts here. Except maybe for one. If you abstain from sexual activity, your chance of cervical cancer will be close to zero.
