Doctors say Pfizer's Lyme disease vaccine trial results 'encouraging' after more than 70% efficacy shown
Earlier this week, pharmaceutical company Pfizer and its partner Valneva announced that an experimental Lyme disease vaccine showed more than 70% efficacy in late-stage clinical trials.
The candidate, PF-07307405, showed 73.2% efficacy in reducing confirmed cases of Lyme disease cases after the fourth and final dose was administered when compared to a placebo.
However, the companies said there were fewer than anticipated cases of Lyme disease during the trial period and the study missed an important statistical benchmark that measures confidence, falling just short of the required 20% threshold at 15.8%.
Experts in tick-borne diseases told ABC News they still need to see the full data from the trials and that it's early to determine what kind of impact the vaccine will have -- but they add that results are "encouraging."
"There are many other companies that are trying to develop something, but those are years and years and years away from being anywhere close to being marketed," Dr. Gene Shapiro, a professor of pediatric infectious diseases and epidemiology of microbial diseases, told ABC News. "So, this vaccine was very similar to the vaccine that we know worked in the past. I think we have to pay attention to [this new one]."
Lyme disease is a bacterial infection that is spread through the bite of blacklegged ticks, also known as deer ticks, according to the Centers for Disease Control and Prevention (CDC).
Symptoms include fever, headache, fatigue and a skin rash known as erythema migrans, the CDC says. If left untreated, the infection can spread to joints, the heart and the nervous system.
More than 89,000 cases of Lyme disease were reported to the CDC by state health departments and the District of Columbia in 2023, according to the latest data available from the federal health agency. Estimates suggest about 476,000 Americans may be diagnosed and treated for Lyme disease annually.
Currently, no vaccine for Lyme disease is available in the U.S. Previously, a vaccine was available, but it was discontinued in 2002, according to the CDC.
"The uptake was poor. The sales were poor, and the company decided to stop selling it," Shapiro said. "The currently developed vaccine [by Pfizer and Valneva] is very, very similar to that vaccine, with very minor modifications."
Dr. Martin Becker, a clinical associate professor in the department of medicine at NYU Grossman Long Island School of Medicine, added that there were concerns raised, including about vaccine recipients having joint problems but several studies examining a link failed to find an association.
Becker said there have been many clinical trials underway "but this one that Pfizer just announced, I believe, is the one that's been most advanced," he told ABC News. "We were eagerly awaiting results from this large Phase III trial. Other previous trials were already published showing the safety and immunogenicity [of the vaccine]."
Pfizer and Valneva said they are planning to file for approval with the U.S. Food and Drug Administration, with Pfizer telling ABC News that the trial results show there is a level of protection against Lyme disease.
"It doesn't mean it doesn't work, but it does mean -- if we had higher numbers of incidence of infection -- we would be more confident about the degree of protection. It's very encouraging," Becker said of not meeting the primary endpoint.
Questions remain about whether the vaccine, if approved, will have higher uptake than the previous vaccine did decades earlier.
Shapiro said there might be more uptake with this vaccine if stronger recommendations are made. At the time the old vaccine was approved by federal regulators, Shapiro said the recommendation from the CDC's Advisory Committee on Immunization Practices was to consider the shot for those at higher risk, but it was not recommended for those at low or no risk.
"It was not a very strong recommendation," Shapiro said. "And I think there was less awareness of Lyme disease. So, most likely, [the newer vaccine] would get a stronger endorsement today."
