TOKYO Zika virus, Ebola, bird flu -- these infectious diseases have put the world on edge and underscored the importance of vaccine development. Yet even if researchers manage to produce vaccines, there is still the challenge of immunizing people on a massive scale.
So while scientists search for preventive agents, they are also chipping away at better ways to administer them. Better, in this case, means less painful, more efficient at getting vaccines into the body, and easy enough for even nonprofessionals to use.
Japan's Terumo has been honing its syringe needles since 1962. Currently, the company is focusing on intradermal injections -- something of a lost art in the medical field.
OUT OF PRACTICE When you get a flu shot, it is typically delivered in the form of a subcutaneous injection, which reaches tissue around 5mm below the surface of the skin.
An intradermal injection, in contrast, delivers a vaccine to shallower tissue between the epidermis and the underlying dermis layer of skin. The cells of the immune system are more plentiful in this shallower layer, so even a small dose has a better chance of achieving the intended results.
Studies suggest that an intradermal injection can be just as effective as a subcutaneous shot with just one-fifth of the vaccine dose, though the precise dosage depends on the vaccine. This is particularly advantageous when there is an outbreak of an infectious disease and vaccine stocks run low.
The downside is that intradermal injections are tricky to administer. The person giving the shot must insert the needle at an angle just below the surface of the skin. This takes skill.
In the past, intradermal injections were a routine procedure. They were used for the tuberculin skin test, used to check whether people are infected with tuberculosis bacteria. But tuberculosis has been largely eradicated, so there are fewer opportunities to administer intradermal injections.
Terumo, though, has a new intradermal syringe that allows the needle to be inserted straight down, rather than at an angle. In addition, the syringe grabs and raises the skin at the point of insertion, making it easier for the needle to penetrate.
"We recognized the need to make these injections safe and accurate so vaccines have their intended effect" regardless of the skill of the administrator, explained Tomokazu Kawase of Terumo's drug and device department.
THIN IS IN This new intradermal device, which Terumo expects to have ready for practical use next fall, stems from the company's efforts to develop a better needle for diabetics who need to give themselves daily insulin injections.
Diabetics who need three injections a day are subjecting themselves to pain more than 1,000 times a year. This constant stress can be mitigated by using thinner needles. Terumo's Nanopass 34G, released in 2012, is the world's thinnest disposable syringe needle. It measures just 0.18mm at the tip.
Naturally, a thinner needle has a smaller inner diameter, meaning more force is needed to push the medicine out of the syringe. To resolve this problem, Terumo designed the Nanopass 34G with a taper. The base of the needle is 0.24mm, so less force is required to plunge the syringe. In addition, the tip has an asymmetrical edge like a knife, so it slices smoothly into the skin rather than puncturing it.
While intradermal injections are gaining recognition as an effective way to deliver vaccines, an entirely new method of transdermal drug delivery is on the horizon: a patch of tiny needles placed on the skin.
PATCH ME UP One company developing this kind of microneedle array is Japan's MEDRx. Its device is a 1cm square that holds 100 microneedles made from biodegradable plastic, each 600 microns long and just 10 microns wide at the tip. The needles are dipped in a vaccine and the patch is placed on the skin. It must be left there long enough for the medicine to diffuse into the body -- from under an hour to several hours. Despite the high number of needles, they are so small that there is very little pain involved.
Microneedle arrays are easy to administer and perfect for individuals who cannot stand the sight of an old-fashioned needle. One caveat: The patch must be placed straight down, otherwise the microneedles will bend and the vaccine will not get into the body.
To solve this problem, MEDRx developed a special applicator that presses the patch onto the skin evenly.
"We wanted a system so vaccines could be administered reliably, even when there is a pandemic and there are not enough doctors to treat everyone," said Yonehiro Matsumura, the company's senior managing director.
Microneedle arrays cannot hold big doses, so they are best suited to vaccines and other medicines that can be delivered in small quantities.
Japan's Nipro and U.S.-based 3M are also developing microneedle array patches. Japan's Fujifilm Holdings is working on a variation of them -- a sheet covered in tiny needles that dissolve, injecting medicine into the body in the process.
Microneedle array patches from these and other companies should hit the market around 2020. Easy, virtually painless injections would smooth the way for large-scale vaccination programs, reducing the threat of pandemics.