Alissa R. Asks: Hi! I had a question which I’m not sure has been addressed. What’s the likelihood of developing some other way of administering vaccines? I keep hearing things about different methods and want to know how much truth there is in it and how close they are to developing another way if any?
Our Answer: That’s a great question! There are a number of methods being explored to create vaccines that are administered some other way besides injection. The challenges with these methods are to create an adequate immune response that is at *least* as good, or better, than what already exists. Briefly, injected vaccines work by recruiting immune cells to the site of the injection: it gets injected into the muscle, and the subsequent inflammation attracts the attention of immune cells, which then ramp up production of specialized cells to fight the particular pathogen the vaccine is designed to protect against. One of the reasons some vaccines contain alum (an adjuvant made with aluminum) is actually to increase the local inflammation to recruit more immune cells. (Think of the alum as the class bully saying, “Yo! Immune cells! You think you’re all that? Well, come and get a piece of this!”)
That’s one of the reasons injected vaccines are so effective and ingested vaccines are so rare. When you ingest the vaccine, the stomach acids can make short work of it before it has time to induce an inflammatory response. (The exceptions are the polio vaccine and rotavirus, who can hack it in the digestive system.) So, to develop additional vaccines that aren’t injected, they need to invoke the same local response. The aerosol flu vaccine does this well because we actually catch flu through the respiratory tract. Creating an immune response in the nose, at the site where we’d normally catch the disease, makes sense. Measles, another respiratory infection, can also have an aerosol-delivered vaccine, and in fact one has been used in Mexico for a number of years. The problem is that it’s not as effective as the injected one. (One of our admins recently wrote about a new study on the aerosol measles vaccine. Notice there that Dr. Poland points out the researchers didn’t measure the local response, which he thinks might have shown a stronger immune response. Both the local and the overall response are helpful to a vaccine’s effectiveness.)
Meanwhile, researchers are continuing to get better at overcoming the challenges of non-injected vaccines. The measles patch could be ready as early as two years from now. And Wired has a nice overview on a couple non-injected methods. Hopefully, we’ll have all sorts of options in the next decade for how we get our vaccines!