Aside from the “ouch factor,” vaccines delivered through a needle in the arm—or elsewhere—have some shortcomings. The needles used to inject vaccines must be kept sterile, for example, which is difficult in some settings. Also, injections usually must be administered by trained personnel, and injecting many people quickly—as would be necessary in case of a widespread outbreak—is not easy. For these reasons, scientists are investigating new ways to deliver vaccines.
Although still a long way off, edible vaccines would make it cheaper and easier to immunize people against diseases, especially in developing countries where storing and administering vaccines is often difficult. Scientists have shown that potatoes genetically engineered to produce an E. coli antigen safely triggered an immune response to this bacterium in people who ate small pieces of the potatoes. Similarly, a potato-based vaccine against hepatitis B virus yielded promising results in an early stage of human testing.
Researchers have also modified bananas to protect against norovirus, a common cause of diarrhea, and have created a food-based vaccine containing a protein from respiratory syncytial virus, which can cause serious respiratory illness, especially in young children.
Recently, research into plant-based vaccines has focused less on food crops and more on genetically modifying plants that are not normally eaten. Vaccine components are produced in the leaves, which are then freeze-dried, ground up, and placed in gelatin capsules.
Patches and Nasal Mist
Another novel way being investigated to deliver vaccines simply is through a thin skin patch. Skin is one of our best defenses against infection. But it also includes large numbers of certain immune system cells, called dendritic cells, which can react to a vaccine placed on the skin. Skin patch vaccines are being tested for a range of diseases, including travelers’ diarrhea, tetanus, anthrax, and seasonal flu.
In 2003, the Food and Drug Administration (FDA) licensed a new vaccine for seasonal influenza that’s delivered as spray into the nose. The vaccine, created with NIAID support, is made from a live, attenuated flu virus. FDA has approved it for healthy people 2 to 49 years old. The vaccine is being tested to see if it can eventually be approved for use in older people and in children under 2 as well. Delivering this vaccine as a nasal mist not only eliminates the needle—making it easier to give to children—but it also closely mimics how the flu virus actually enters your body, which may produce a better immune response.
Universal and Therapeutic Vaccines
A nasal flu vaccine eliminates the dreaded needle, but people must still get the vaccine every year because the circulating influenza virus strains change. The annual flu shot may become a thing of the past, however, if researchers working on a so-called universal flu vaccine succeed. To make a universal flu vaccine that would work for more than a year, scientists incorporate parts of the flu virus that do not change very much.
Typically, vaccines prevent infection or disease. More recently, researchers also have been creating therapeutic vaccines designed to battle an existing infection or illness. Several such vaccines are in various stages of development, including ones against some cancers, HIV, certain allergies, and multiple sclerosis.