Just one year ago, a number of Midcoast residents were participating in a clinical study to help develop a vaccine against Lyme disease. This Pfizer Lyme vaccine study was coordinated locally by MaineHealth Pen Bay Hospital Clinical Research, in Rockport, and in conjunction with Tufts University.  But its reach was also international, and was being studied at sites in areas of high Lyme disease incidence in the United States, Canada and Europe.

The Midcoast and Penobscot Bay region, most prominently Knox, Lincoln, Waldo, and now Hancock, counties, continues to be Maine's epicenter for tick exposure and the five bacteria, tick parasite and virus that can cause grave illness in humans.

This particular study, lead by Pfizer and the French company Valneva, had been under way since 2023, and had a target completion date of December 31, 2025. 

In late March 2026, Pfizer said in a news release that the vaccine candidate, "PF-07307405 (LB6V) demonstrated more than 70% efficacy in preventing Lyme disease in individuals aged five years and above," and that, "the investigational vaccine candidate was well tolerated with no safety concerns identified at time of analysis."

According to the University of Minnesota's Center for Infectious Disease Research Policy: "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."

Pfizer said the study results strengthened confidence in the vaccine and the company would be planning submissions to regulatory authorities.

A year-long extension of that study is now in progress at MaineHealth Pen Bay Hospital. The extension is only open to participants who were enrolled in the first phase of the study.

Pfizer said: "This investigational multivalent protein subunit vaccine uses an established mechanism of action for a Lyme disease vaccine that targets the outer surface protein A (OspA) of Borrelia burgdorferi, the bacteria that cause Lyme disease. When a person is immunized with PF-07307405, their body creates antibodies against six Borrelia OspA serotypes. As the tick feeds on the vaccinated person, these antibodies are ingested by the tick as part of its blood meal. Binding of vaccine-induced antibodies to OspA on Borrelia inside the tick inhibits the bacterium’s ability to leave the tick, preventing it from being transmitted to the human host. The vaccine candidate covers the six most prevalent OspA serotypes expressed by the Borrelia burgdorferi sensu lato species in North America and Europe."

During the vaccine study, trial participants five years of age and older were randomized 1:1 into two trial groups and received four doses of either PF-07307405 or a saline placebo – one dose administered at months 0, 2, 5-9 followed by a fourth dose one year later, shortly before the start of the following Lyme disease season, said Pfizer.

The Pen Bay Hospital 2025 research included 78 participants, many of them local residents. Fifty percent of the participants received the Lyme vaccine while 50 percent received a placebo. Participants were to be informed sometime in 2026 if they were given the placebo or the investigational Lyme disease vaccine.

Pen Bay is the only MaineHealth hospital and one of only two sites in Maine participating in the study, which was open to healthy adults ages 18 and older who live in or regularly visit areas that may expose them to ticks.

According to Maine's Tick Lab, there are, "15 different tick species that have been found in Maine, though not all are permanent residents. Some may arrive in the state on wildlife hosts and do not establish viable populations. Other species have thrived in Maine and are now widespread throughout much of the state."

As of April 7, 2026, there were 393 cases of Lyme Disease in Maine, eight cases of Anaplasmosis, and nine cases of Babesiosis. The Knox/Lincoln/Waldo County area combined was reporting 103 cases and Hancock County reported 48 cases, according to the Maine Tracking Network, a division of the Maine Center for Disease Control and Prevention.

Despite the cold winter, ticks remained active, as local residents can attest. With Spring, the dog ticks are out, soon to be followed by the deer tick nymphs — little pin-head sized ticks that resemble a large grain of ground pepper.

The 2024 Tick Surveillance Program Annual Report notes that the Black legged tick (deer tick) life stage, "can be important in the disease transmission cycle, as adults are more likely to be infected with a pathogen, but the smaller immature nymphs can easily go unnoticed for long periods of time while feeding."

Maine tests the ticks that people send to the state lab (4,776 in 2024) for pathogens. Those pathogens include Lyme Disease, anaplasmosis, babesiosis, hard tick relapsing fever, and Powassan virus. In 2024, Lyme was the most prevalent in the 2,715 black-legged ticks and 629 nymphs that were tested, but the other pathogens were also present to a degree. The Powassan virus appeared in ticks that came from Knox, Lincoln, Waldo, Hancock and other coastal counties.

"People acquire Powassan through the bite of an infected deer or woodchuck tick," the Maine CDC said in 2024, when reporting a death from the rare tick-borne illness in York County. "Deer ticks can be active any time the temperature is above freezing, but are most active in the spring, summer, and fall. Powassan virus may spread from ticks to people in as little as 15 minutes after a bite."

Ticks are a regular part of life in Maine now, for humans and pets. While dogs are vaccinated and treated monthly with preventative medicine, they still can suffer from flare-ups if they were ever infected and despite doses of antibiotics. 

Humans are not, however, preventively treated, and there is no vaccine, yet, for Lyme. It falls on exposure management to keep ticks at bay. While medical research continues, so too will Mainers remain vigilant to reducing exposure to ticks.

Beef up personal protection

• Wear EPA-approved repellents.
• Avoid wooded and brushy areas with high grass and leaf litter. Walk in center of trails.
• Wear long-sleeved, light-colored clothing. Tuck pant legs into socks and shirts into pants.
• Check clothing and gear for ticks and do a full-body tick check when returning indoors. Pay special attention to under the arms, behind the knees, between the legs, in and around the ears, in the belly button, around the waist, and in the hair. 
• Take a shower within two hours after spending time outdoors, which will wash off unattached ticks. 

Repellents

• Use repellents that contain 20 percent DEET or greater to effectively repel ticks for several hours. Other EPA-approved tick repellents for use on skin include picaridin, oil of lemon eucalyptus, and IR3535.
• Products containing permethrin can treat clothing/gear and last for several washes. Permethrin treated clothing is shown to be highly effective at preventing tick bites.
• In general, products containing natural ingredients tend to be less effective at repelling ticks than other EPA-approved repellents.
• Follow label instructions.