Compositions for coating microneedles with aluminum-adjuvanted vaccines are provided comprising an aluminum-containing wet gel suspension selected from aluminum hydroxide wet gel suspension and aluminum phosphate wet gel suspension; a vaccine in an amount effective to stimulate an immune response in a mammal; a sugar, sugar alcohol, or combinations thereof; and a thickener. Some embodiments of the compositions have a viscosity of 500 to 30,000 cps when measured at 100 s−1 and temperature of 25° C. Microneedle devices coated with the compositions, as well as methods of forming the compositions and coating the microneedles, and methods of maximizing the aluminum content of vaccine-coated microneedle arrays are also provided.