Study: Older Vaccination Method May Be More Effective

New research out of Brigham and Women's Hospital shows that giving a vaccine through a scratch in the skin can be more effective than injecting a vaccine into the body.

The method, called scarification, is done by scratching the skin repeatedly with a sharp needle and then applying a solution that contains a virus.

It's actually an old-fashioned approach that was used to administer the smallpox vaccine nearly two centuries ago, according to Dr. Thomas Kupper, the study's senior researcher.

With certain vaccines, this scratching method gets a better immune response and requires a much smaller amount of vaccine, said Kupper, a professor at Harvard Medical School and chairman of the dermatology departments at Brigham and Women's and the Dana-Farber Cancer Institute.

Another advantage of scarification (pronounced SCAR-ification), Dr. Kupper added, is that it would be easy to do in the world's most remote places, where medical resources are scarce.

"This could be done in the Amazon jungle or the steppes of Mongolia or any place else," he said. "You simply don't need the sorts of things you need for the hypodermic syringe method. Nor do you need the same amount of equipment.

"So in terms of the expense and feasibility of doing this on a grand scale," he added, "I think it's got real promise."

Most vaccines today are administered by injecting a hypodermic needle into fat below the skin, or into muscle. This method is cleaner than earlier techniques, and it allows vaccine doses to be measured very precisely.

It isn't entirely clear why scarification can be more effective than an injection, according to the researchers.

But while it may seem counterintuitive that an older vaccination technique would be superior to a more modern one, there's an evolutionary logic to why the body would respond so well to a vaccine delivered through a scratch in the skin.

According to Dr. Kupper, in pre-modern times, the body's immune response was typically triggered by an injury to the skin's outer layer — such as a tearing bite by a wild animal that enabled a virus or bacteria to enter the body — and not by a syringe being plunged directly and deeply into muscle or subcutaneous tissue.

As a result, the human immune system "was built to respond beautifully to things that it sees through breaches and breaks in the skin," which closely mirrors the scarification method, Dr. Kupper said.

This older technique may not be more effective with all vaccines, he added, but "it certainly means we should rethink how we deliver some vaccines."

The study (PDF) appears in the current issue of Nature Medicine.