Pfizer-Valneva Lyme vaccine shows more than 70% efficacy but misses key goal

March 23 (Reuters) – Pfizer and Valneva said on Monday their Lyme disease vaccine showed more than 70% efficacy in a late-stage study, even as it missed its main goal.

Despite falling short of a key statistical requirement meant to ensure reliability, Pfizer said the overall results give it confidence in the vaccine’s potential and it plans to move ahead with regulatory submissions.

U.S.-listed shares of the French drugmaker tumbled nearly 37% following the update, while Pfizer was marginally down.

The vaccine demonstrated 73.2% efficacy starting 28 days after the fourth dose in reducing confirmed Lyme disease cases, compared to the placebo.

However, the companies said the trial was designed to show that this benefit had a confidence interval of at least 20%. In the first analysis, that figure came in slightly lower at 15.8%, largely because fewer Lyme cases than expected were recorded during the study, limiting the data.

A second planned analysis a day after the fourth dose, not 28 days, met the bar, the companies said.

RBC Capital Markets analyst Trung Huynh said regulators could take a “sympathetic” view given there is no approved vaccine for Lyme disease, which is spread by infected black-legged ticks and affects about 476,000 people annually in the United States.

GSK discontinued its Lymerix shot in 2002, citing insufficient demand.

Cantor analyst Carter Gould struck a more cautious note and said that while the data are “directionally supportive” of approval, they are not as strong as “some bulls” had hoped for.

Lyme disease can cause fever, headache, fatigue and a characteristic skin rash, and if left untreated, can spread to the joints, heart and nervous system. Most cases can be treated with a few weeks of antibiotics.

Last year, Valneva said it expects Pfizer to launch the vaccine in the second half of 2027 following approval.

(Reporting by Puyaan Singh in Bengaluru; Editing by Sriraj Kalluvila and Maju Samuel)