Vaccines make a crucial contribution to public health, saving hundreds of millions of people from deadly or debilitating diseases every year, but it’s also fair to say that getting your shots is not the most pleasant of experiences. It’s not just a question of short term discomfort, many people suffer from needle phobias that can prevent them from getting necessary vaccination, and wherever you have used used hypodermic needles there is always the question of safe disposal of this biohazardous waste and the risk of needle stick injury. Now research conducted on mice and pigs at Emory University and the Georgia Institute of Technology shows that there may be a safer and less painful way to administer vaccines (1).
The new vaccine patch uses an array of one hundred tiny needles to deliver the vaccine painlessly into the skin, but the clever part is that having done so the needles, which are made from a polymer material known to be safe for clinical use, dissolve within a few minutes so there is no hazardous sharps waste to be disposed of. This is a significant advantage over previous microneedle patches that used metal or silicon needles. The vaccine is also injected in a solid form which makes it stable and less likely to break down in storage, an important consideration for clinics in developing nations and remote areas of the world.
So how do they know it works? Well they first had to make sure that the needles could deliver the vaccine into skin without breaking, and then quickly dissolve. The team led by Sean Sullivan assessed this using skin obtained from freshly slaughtered pigs, because pig skin is very similar to human skin in thickness and structure, and found that the microneedles delivered the vaccine successfully and then quickly dissolved.
Of course delivering a vaccine into the skin is not enough, you have to know if that vaccine will stimulate the desired response from the immune system. The team needed to assess whether the vaccine patch could provoke an immune response that is strong enough to protect against subsequent infection, and this is something that can only be properly done in a living animal. When the vaccine patch was used to immunize mice with an influenza virus vaccine it provoked a robust and sustained response from the immune system, one that was in fact better than that observed with traditional intramuscular injection. Furthermore the vaccine patch immunized mice survived when infected with influenza virus three months after immunization, whereas all non-immunized control mice died.
Vaccine patches promise a safe, painless and cheap alternative to vaccination via hypodermic needle, and as someone who likes to keep their shots up to date I’m hoping that this new method will succeed in human trials and soon be available in the clinic.
1) Sullivan S.P. et al. “Dissolving polymer microneedle patches for influenza vaccination” Nature Medicine, Published Online 18 July 2010 DOI:10.1038/nm.2182