An experimental six-strain Lyme vaccine has demonstrated more than 70% efficacy in preventing Lyme disease in people aged five years and older, according to a statement yesterday from Pfizer. 

Despite falling short of its primary statistical goal in a phase 3 randomized controlled clinical trial, in part because fewer than expected Lyme disease cases were reported during the study period, the vaccine showed about 70% to 73% efficacy in preventing confirmed Lyme disease after a four-dose series. In a secondary analysis, the vaccine did meet the statistical goal. 

The vaccine, being developed by Pfizer and Valneva, was studied at sites in areas of high Lyme disease incidence in the United States, Canada, and Europe.

Pfizer said the reduction in infections is “clinically meaningful” and indicated that the companies will submit the vaccine for regulatory approval. If approved, it would be the first Lyme vaccine available for humans in more than two decades.

Vaccine blocks bacteria from leaving the tick

The new vaccine candidate, known as PF-07307405 (LB6V), is a multivalent protein subunit vaccine that targets the outer surface protein A (OspA) of Borellia burgdorferi bacteria. When a person is vaccinated with LB6V, the body creates antibodies that are ingested by the tick as it feeds on the vaccinated person. 

When the antibodies bind to OspA inside the tick, it prevents the bacteria from leaving the tick and entering the human bloodstream. The vaccine is designed to protect against the six most common versions of OspA found in Lyme-causing bacteria in North America and Europe. 

The vaccine prevents the bacteria from leaving the tick and entering the human bloodstream.

“Lyme disease can cause potentially serious consequences—where individuals and families face symptoms that can disrupt daily life, work, and long-term health—and there is currently no vaccine available,” Pfizer Senior Vice President and Chief Vaccines Officer Annaliesa Anderson, PhD, said in a statement. “The efficacy shown in the VALOR study of more than 70% is highly encouraging and creates confidence in the vaccine’s potential to protect against this disease that can be debilitating.”

Rising vaccine skepticism may cast shadow

A previous vaccine, LYMERix, was approved for use in people in 1998. Research conducted at that time suggested LYMERix reduced infections by as much as 76%, and no causal link between the vaccine and adverse events was ever established. But reports of adverse reactions began to circulate in the press, and safety concerns tanked sales. GlaxoSmithKline (now GSK) pulled the vaccine from the market in 2002 because of low consumer demand.

The new Pfizer/Valneva vaccine is likely to face increased scrutiny. As head of the Department of Health and Human Services, Robert F. Kennedy Jr. has pushed an anti-vaccine agenda, dismantling federal immunization advisory boards and rebuilding them with vaccine skeptics and slashing the number of recommended childhood vaccines. (A federal judge recently blocked the Trump administration from implementing its proposed changes to the childhood vaccine schedule.)

Moderna is currently developing an mRNA-based Lyme vaccine candidate. Recruitment for the phase 1/2 trial is ongoing. 

A Lyme disease vaccine for dogs has been on the market since 2016. 

Roughly 476,000 patients are diagnosed as having Lyme disease each year in the United States. The condition is caused by B burgdorferi spirochetes, which are transmitted to humans by certain Ixodes species ticks known as black-legged or deer ticks. 

Infection can affect multiple organ systems and is usually treatable with antimicrobial drugs. When not caught early and treated, Lyme disease can cause serious, long-term health issues such as heart problems, chronic inflammation and joint pain, and neurologic problems.  

In the United States, most Lyme disease cases occur in the Upper Midwest and along the northeastern seaboard. Ticks carrying the B burgdorferi spirochetes are also found in parts of Central and Northern Europe. Lyme disease is considered the most common vector-borne illness in the Northern Hemisphere.