A comparison of two methods for delivering influenza vaccines has concluded that dissolvable microneedles perform at least as well as the traditional hypodermic. Microneedle patches could have advantages both in delivering vaccines to remote locations and in overcoming resistance to vaccination.

Microneedles replace a single large needle with numerous needles so small they can barely be seen or felt, each delivering a fraction of the dose required to induce an immune response in the patient. Attached to a patch, they can be placed on the skin to slowly deliver the vaccine.

However, early attempts at using microneedles ran into problems. These needles were made of hollow silicon or metal, often leaving the vaccine recipient with tiny fragments under the skin, which become the entry sites for secondary infections.

Professor Shinsaku Nakagawa of Osaka University has taken a different approach, creating microneedles out of hyaluronic acid, a substance the body produces to cushion joints from impact. Hyaluronic acid dissolves in water, or the skin for that matter, eventually leaving no trace.

In the journal Biomaterials, senior author Nakagawa reported on a trial of microneedle patches to deliver A/H1N1, A/H3N2 and B flu vaccines. The trial did not investigate how many of the people receiving the vaccination subsequently got sick, but it did measure their immune system response to each of the flu strains.

Blood samples were taken two, 7 and 21 days after vaccination. Immune responses were the same to A/H1N1 and A/H3N2 for both delivery mechanisms, but those using the patches had a stronger antibody response to B strain influenza than those who received an injection.

Influenza vaccines need to be given every year, because the viruses that cause the disease are constantly evolving. Vaccination is normally only given against the three most common strains at the time.

“Conventional vaccinations are administrated with subcutaneous or intramuscular injections, which require medical personnel with technical skills and is accompanied with the risk of needle-related diseases and injuries,” the paper notes. “Moreover, antigen solutions require cold chain storage and transportation systems. Therefore, the development of vaccines, which are easy-to-use in administration and superior in stability of formulations, is critically important.”

“We were excited to see that our new microneedle patch is just as effective as the needle-delivered flu vaccines, and in some cases even more effective," said Nakagawa. "We have shown that the patch is safe and that it works well. Since it is also painless and very easy for non-trained people to use, we think it could bring about a major change in the way we administer vaccines globally."

Familiarity, and confusion with the common cold, has taken away the fear of flu for many people. However, it continues to kill around 250,000 to 500,000 people in an ordinary year, and a pandemic such as those experienced in 1918, 1957 and 1968 is only a matter of time, so a mechanism that boosts vaccination rates is important, particularly if it can be rolled out quickly in an emergency.