One of the handy things about vaccines is that once a sufficient proportion of the population has been vaccinated, even people who haven’t been have lower rates of whatever disease the vaccine protects against. That’s because the virus, now facing a housing shortage of sorts, cannot spread as widely. Think of it this way: if you are not vaccinated against it, you might catch the flu from a person on the subway and then pass it on to your roommate. But if you are vaccinated against it, the virus can’t spread to you and from you to your roommate. Even if she is not vaccinated, your roommate is protected from catching the flu (at least from you). The phenomenon is called herd immunity.
Now, researchers are reporting that the HPV vaccine, which protects people from a strain of human papilloma virus that causes cervical cancer, may already be helping lower the rate of infection even in people who aren’t vaccinated. The study looked at rates of HPV infection in teens and young women at two primary care clinics before the vaccine went on the market and several years afterwards, and found that infections from the cancer-causing HPV strain were down, from more than 30% to around 13%. What was interesting was that the drop wasn’t just due to vaccinated women not having the disease; even when the researchers just looked at women who hadn’t been vaccinated, their rates were down to 15%.
Where viruses and bacteria cause cancer
Strictly speaking, cancer is not contagious. But a fair number of cancers are clearly caused by viral or bacterial infections: lymphomas can be triggered by the Epstein-Barr virus, which also causes mononucleosis. Liver cancers can be caused by Hepatitis B and C. Cervical cancers can be caused by human papillomavirus, the major reason behind the development of a vaccine against it. For some of these cancers, nearly 100% of the cases have an infectious link—when researchers check to see if a virus or bacterium is working in the tumor or has left signs of its presence in a patient’s blood, the answer is nearly always yes.
A new paper in The Lancet takes a look at the very best data on the prevalence of infection-caused cancers and comes up with some striking numbers. Overall, they estimate that 16% of cancer cases worldwide in 2008 had an infectious cause—2 million out of 12.7 million.
Over the past four years, a controversy has erupted over whether to routinely give girls the new vaccine against the human papillomavirus (HPV), a sexually transmitted virus that can cause genital warts and cervical cancer. Now we can have the debate all over again–but this time, with boys. An advisory panel of the Food and Drug Administration has recommended that the vaccine be made available for boys as well. While boys are obviously not at risk for cervical cancer, HPV can give them genital warts and, in very rare cases, can lead to anal or penile cancer.
The pharmaceutical giant Merck makes the first HPV vaccine available in the United States, Gardasil, which is considered most effective when given to young people who aren’t yet sexually active and therefore haven’t yet encountered the virus. But analyst Tim Anderson says that the regime of three shots over six months may deter some customers. “You are asking a healthy teen to come to the doctor three times in six months,” Mr. Anderson said…. “Pretty much no healthy teen would ever do that, let alone to come back and get a shot” [The New York Times]. It may be a particularly hard sell because most cases of genital warts clear up naturally, and because anal and penile cancers are so rare–each year they’re diagnosed in about 2,100 and 1,300 American men respectively.
Related Content:DISCOVER: How We Got the Controversial HPV Vaccine
DISCOVER: The Battle Over the Cervical Cancer Vaccine Heats Up
80beats: Male Circumcision Cuts Risk of HIV, Herpes, and HPV Transmission
80beats: Nobel Prize for Medicine Awarded to Virus Hunters
Image: flickr / lu_lu
Researchers now have solid evidence that male circumcision protects against three viral sexually transmitted diseases (STDs), and say their findings should encourage parents around the world to circumcise their infant boys. A large study in Uganda involving 5,534 men found that those who underwent circumcision as adults were 25 percent less likely to become infected with herpes and more than 30 percent less likely to catch human papillomavirus (HPV) than their uncircumcised peers…. Previous research has shown that circumcision reduces a man’s risk of acquiring HIV by as much as 60 percent [Scientific American].
Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, says that the area beneath the foreskin of an uncircumcised male provides the “perfect breeding ground for viruses and bacteria.” It can tear and develop sores easily, and if it becomes inflamed, he said, “it gives you much more fertile ground for HIV to be transmitted” [Scientific American], as well as the herpes and HPV viruses. However, the study did not show protection against syphilis, a bacterial STD.
Three researchers who discovered viruses that cause serious diseases have been awarded the Nobel Prize in medicine, the Nobel Foundation announced today. The prize was awarded jointly to France’s Francoise Barre-Sinoussi and Luc Montagnier, who worked together to identify the HIV virus that causes AIDS, and also to the German scientist Harald zur Hausen who discovered the human papilloma viruses (HPV) that can cause cervical cancer.
Barre-Sinoussi, who is the eighth woman to win the medicine prize since the first Nobel Prizes were handed out in 1901, worked with Montagnier to discover the HIV virus. Shortly after reports in the early 1980s of a new immunodeficiency syndrome, researchers all over the world raced to find the cause. The two [researchers] cultured cells from lymph nodes of patients. They first detected the enzyme reverse transcriptase, which meant that a retrovirus was active. Further searching turned up retroviral particles, which could kill white blood cells and which also reacted with antibodies from infected patients [Scientific American].