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%.
An extensive study conducted on school children in Western Canada has proved that immunizing kids and adolescents goes a long way towards protecting the entire community from communicable diseases like the flu, thanks to a phenomenon known as “herd immunity.”
The findings come at a time when vaccine phobia is one of our largest public health concerns, with many parents worrying that immunizing kids can lead to adverse side affects. A recent survey revealed that one in four U.S. parents think that vaccines might cause autism, probably due in part to a 1998 paper published in the journal The Lancet that wrongly linked autism to vaccines–that paper has since been refuted, and fully retracted by the journal.
Now, scientists have more evidence that vaccines provide a public health benefit. Researchers studying youngsters in 49 remote Hutterite farming colonies in Canada found that giving flu shots to almost 80 percent of a community’s children created a herd immunity that helped protect unvaccinated older people from illness. As children often transfer viruses to each other first and then pass them along to grown-ups, the study provided solid proof that the best way to contain epidemics like the recent H1N1 outbreak is to first vaccinate all the kids. By immunizing the most germ-friendly part of the herd first, you indirectly protect the rest of the community, scientists say.