Pfizer’s Long-Awaited Lyme Vaccine Fails to Impress in Study (2)

Pfizer Inc. said its experimental Lyme disease vaccine was 73% effective against the tick-borne illness, a lackluster result as fewer-than-expected infections in the pivotal study made its potency hard to evaluate.

While the vaccine reduced cases of Lyme, it did not clearly meet expectations set before the trial began. The shot that’s being developed with the French biotechnology company Valneva SE was given to people in the US, Canada and Europe who were at high risk of exposure, but fewer than expected got infected, confounding the results.

The companies said they are confident about the vaccine’s potential and plan to ...