It's been two years since the U.S. Food and Drug Administration approved Gardasil, the first vaccine to help prevent cervical cancer and other conditions caused by particular types of genital human papillomavirus (HPV). HPV is the most common cause of new sexually transmitted diseases. According to the first national estimate of use, 25 percent of teenage girls received at least one dose of the Gardasil vaccine in 2007, with 20 million doses distributed in U.S. The HPV vaccine has made news frequently, as parents weigh the benefits, the high cost, claims of adverse reactions and unease about vaccinating their kids from a sexually transmitted disease. We talk to Lydia Shrier, MD, MPH, about these concerns, and the potential of Gardasil.
What is HPV and how prevalent is it in the U.S?
It is a group of more than 100 different types of viruses, more than 30 of which are sexually transmitted. Low-risk types of HPV can lead to benign, but bothersome, genital warts or abnormal changes in the cervix, but generally don't progress to serious disease. However, high-risk types can lead to cervical cancer and, rarely, cancers of the vulva, vagina, anus or penis. There is no cure for HPV and a person can have more than one type. The vast majority of sexually active people, by the end of their life, will have been exposed to the virus. Most people who have acquired HPV infection don't know that they have it because they don't have any symptoms. Pap smear screening is where we detect abnormalities that lead to cervical cancer.
Gardasil, a vaccine against HPV, was released in 2006. How effective is it at protecting women from HPV?
Gardasil is very effective in preventing acquisition of infection from four types of HPV--the two types that cause more than 70 percent of cervical cancer, and the two types that cause 90 percent of the cases of genital warts.
The CDC recently released statistics showing that 25 percent of teenage girls have received Gardasil to protect against cervical cancer. Is this a good start?
Currently I'm recommending Gardasil for all of my teenage patients. I would like it to be 100 percent. Every year in the United States, there are over 11,000 new cases of cervical cancer and more than 3,800 deaths from cervical cancer. With the vaccine, we have the opportunity to offer protection to young women before they've been exposed to HPV.
Why do you think it hasn't been more widely accepted and used?
There are lots of reasons. It's new. Some parents think they can wait until their daughters are older, because they don't think their daughter is going to be sexually active anytime soon. Some parents might be concerned that there are adverse reactions to the vaccine, as it has been in the news lately. Uptake of a new preventative behavior by both physicians and patients always takes time.
Is there a high rate of adverse reactions to Gardasil?
The rate of adverse effects is not any higher than other vaccines. Proportionally, there are actually fewer serious adverse events with the HPV vaccine than with other vaccines. As with any vaccine, new or otherwise, there's a reporting system of physical symptoms after receiving the shot. Those are reviewed and investigated to see whether there is any possibility of causality. Just because someone gets sick after the shot doesn't mean the shot caused them to be sick. This vaccine is not a live vaccine; it does not give you a little case of HPV. To date, the Centers for Disease Control and Prevention (CDC) has not found a causal relationship that would warrant any change in the recommendations.
Why do you believe it's so important for girls to get the vaccine?
It's very exciting to have a vaccine that has a potential to prevent cases of cervical cancer. Our ability to prevent cases before the availability of the HPV vaccine focused on counseling around sexual contact to limit exposure and, once exposure occurred, Pap smear screening to detect precancerous abnormalities. Those things still need to happen and are very important, but now we have a third prong to our approach. What we know about the vaccine at present suggests very little downside to getting it and I think the potential benefits outweigh that minimal risk.
What do you say to the parent who is worried that Gardasil hasn't been studied for long enough?
It has been studied for years, and the safety profile is very good. I tell my patient families that my understanding of the data gives me the confidence to recommend the vaccine.
Studies have shown that the vaccine works best in women who have not been exposed to HPV--does this mean that it is not worth getting if you are already sexually active?
It's important to try to immunize women early, before they have been exposed, to maximize the efficacy of the vaccine in preventing HPV infection. However, we absolutely still vaccinate sexually active young women. We don't know if these young women have acquired any or all of the types of HPV targeted by the vaccine; the vaccine will be effective against any one of the four types they haven't acquired.
There have also been questions raised about how long the protection lasts. How long are women are protected for, and will they need a booster shot to remain protected?
The five year data show women are still protected. There isn't any evidence to suggest waning immunity. The idea behind the vaccine is to buy some time. You want to vaccinate young women who haven't been exposed and protect them during the time in their lives when they are most likely to be having new sexual contacts.
Why is it important for women to have regular gynecologic exams?
There are precancerous stages of cervical abnormalities that can be treated before cancer develops. The only way we can pick up these abnormalities is with a Pap smear. We need to communicate to women that there's still a risk of getting cervical cancer, with or without the vaccine. Because of the internal location of the cervix, you don't necessarily know you have cancer, or abnormalities that could lead to cancer, unless you get a Pap smear.
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