Lyme disease affects nearly half a million Americans annually. Pfizer and Valneva are developing the VLA15 vaccine against Lyme disease, which is the most advanced in clinical development. In the phase 2 study VLA15-221, 560 healthy participants were randomized to receive the vaccine in two vaccination schedules or placebo. After the third booster dose at month 42, participants achieved 100% seroconversion against all six outer surface protein A serotypes in all age groups – children, adolescents and adults. Antibody levels and safety profile were similar to previous booster doses, with no problems noted. The vaccine is intended for annual booster doses before the Lyme disease season. Two phase 3 trials are nearing completion, with US and EU registration applications expected in 2026. There is currently no Lyme disease vaccine approved in the US.[1][2][3][4][6]