Just about all of us appreciate the health benefits of vaccination, even if few enjoy the sensation of getting a jab. While children and animals are most notorious for expressing resistance to inoculation, adults don't exactly look forward to the experience either. Yet despite the considerable recent advances made in vaccine platform technology — including the development of smaller, less painful needles — the trypanophobic among us might feel that there will never be a future in which "vaccine" and "ouchie" don't automatically go together.
Yet for decades, a group of enterprising biomedical engineers have bene working to figure out the answer to this question: Can we design vaccines without needles, that still inoculate a patient with a serum that enters the bloodstream?
The idea has been a mainstay of science fiction for years: Think of the so-called "hyposprays" on "Star Trek," which inject with a quick hiss and without needles.
But the idea of a hypospray is no longer merely fiction. Indeed, needle-less vaccines do indeed exist, and they could be the future of vaccination.
"A needle-free injection is, especially when the machine has been developed appropriately, a very good way to deliver the vaccine."
Beyond inoculation, there are actually a wide range of vectors that can be used to administer vaccines in a needle-free manner. Drugs can be delivered through the skin using Lorentz force, which combines electric with magnetic forces to shoot through the vaccine into the body. Gas and electricity can be used to propel a vaccine through a patient's skin, or shock waves can figuratively blast it into the body. Known in short as NFJIs (needle-free jet injectors), these can be administered within the skin, underneath the scene or directly into the muscle. In addition to psychological helping trypanophobic patients, NFJIs also have value when doctors need to engage in dose-sparing, or administering less than the recommended amount of a vaccine (which can happen due to anything from shortages to potential health issues with a specific patient).
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Dr. William Haseltine, a biologist renowned for his work in confronting the HIV/AIDS epidemic, told Salon that the technologies at play here have "been around for quite some time." They can be broadly lumped into several categories, both of them depending on the underlying mechanical principle being utilized.
"The first one is to, under pressure, create a liquid stream that penetrates the surface of the skin," Haseltine explained, such as one that may use shock waves to propel a drug through the skin. He added that there are needleless COVID-19 vaccines in India and China of a somewhat different nature; a nasal COVID vaccine in India gets squirted through the nose, and a Chinese COVID vaccine is sprayed into the mouth — and, notably, it is unclear how effective either of those inoculations actually are. In the case of the Chinese version, they are only being given as boosters rather than as substitutes for an initial shot.
Similarly, Haseltine noted that when it comes to vaccines that use a machine to send the vaccine through the skin, there are questions about whether all of the drug winds up entering your body.
"People have worried under some circumstances that there is with a variety of different devices some leakage back into the machine once you blow the liquid into the arm," Haseltine explained, adding that now "there are new devices that get around that." He also noted that, when it comes to those NFJIs that propel a liquid into the user's dermis (or skin), there could be an advantage because it is not going into the muscle.
"The dermis is a good place for the vaccine to be because you have a very well-developed immune system there."
"The dermis is a good place for the vaccine to be because you have a very well-developed immune system there, rather than sticking into a muscle which doesn't really have a well-developed antigen-detection system," Haseltine pointed out. "It puts it right into the skin, which has probably one of the very, very best, if not the best protection, where you have them the most, with what are called dendritic and Langerhans cells."
While muscles may not be the best place to inject from an immunological standpoint, there are reasons that nurses prefer them. Indeed, vaccines that are not injected in the muscle run the risk of hitting a blood vessel, which can cause adverse reactions.
"A needle-free injection is, especially when the machine has been developed appropriately, a very good way to deliver the vaccine," Haseltine concluded.
Dr. Georges Benjamin, the executive director of the American Public Health Association, also told Salon by email that a lot of progress has been made in developing the technology behind NFJIs.
"Substantial progress has been made in animal (mouse) models," Benjamin noted. "The mucosal vaccine generates strong humoral and cellular responses. It possibly generates sterilizing protection meaning it may prevent reinfection of vaccinated people; which if this occurs in humans would be superior to the current intramuscular vaccine."
At the same time, Benjamin warned that there are still many hurdles that these vaccines will need to surmount, at least when it comes to the needleless COVID-19 vaccines.
"Substantial clinical trials in humans is needed with enough minorities, non-pregnant and pregnant women, and children included," Benjamin wrote to Salon. "The fact that so many people are vaccinated or previously infected reduces the pool of people eligible for such studies so different study designed will be needed. Also robust safety studies will still be needed. The impact on long COVID is unknown "
In addition, some of the supposedly needle-less vaccines are not, well, technically needless. In the latter case, however, that may not be such a big deal.
"The second one may not be exactly needle free, but it uses microneedles, so you'd never know there is a needle there," Haseltine told Salon. "It's like a skin patch, but it has a series of very tiny needles that you don't feel, and that goes also into the dermis. It's a dermal patch with microneedles. They can just be put on a Band-Aid and the needles would be coded with the vaccine."
Update: This article has been updated to use the correct version of the term "humoral."