Microneedle: Effective Means for Vaccination

Vaccines have greatly contributed to the prevention of infectious diseases. Most current vaccines are inoculated by intramuscular or subcutaneous injection using syringes. These inoculation methods involve pain, bleeding, fear, needlestick accidents. One promising method that can overcome these disadvantages is vaccination using microneedles. MN materials are already FDA-approved for implantation or parenteral delivery for other applications. MNs can increase the transdermal permeability and deliver vaccine compounds including proteins, genetic materials and so on. There are several types of microneedles. Among them, a number of research and development has been carried out on coated MN and dissolving MN. The surface of coated MN is coated with the vaccine. On inserting into the skin, the vaccine is directly deposited into the epidermis or the upper dermis layer. Dissolving MNs are fabricated with biodegradable polymers by encapsulating the vaccine into the polymer. After inserting dissolving MN into the skin, dissolution takes place which releases the vaccine. Conventional influenza vaccines and universal vaccine candidates have been shown to be delivered to the body using MN and to have effective immunogenicity. DNA vaccines are simple to induce both of cellular and humoral immune response that make them attractive vaccine candidates. A disadvantage of DNA vaccines is their poor immunogenicity in intramuscular administration. Hepatitis B virus DNA has been shown to induce effective immunity by administration using MN with an adjuvant. This review introduces concrete works for microneedle vaccines against influenza and hepatitis B.