An adult female deer tick. Credit: Courtesy of Griffin Dill

Mainers will be able to participate in clinical trials for a Lyme disease vaccine later this year, as the Brewer-based Northern Light Health system partners with Pfizer to help it run the next round.

Northern Light estimates about 100 patients age 5 and older will participate in the trial to test the efficacy of the vaccine developed by Pfizer and the French company Valneva, though Pfizer would welcome as many participants as possible, said Dr. Rung-chi Li of Northern Light Allergy and Immunology.

Most people in Maine will be eligible for the trial, especially those who engage in outdoor activities such as hiking or gardening that put them at a higher risk for contracting Lyme disease, Li said.

It’s been 20 years since a Lyme disease vaccine has been on the market, and the infection’s prevalence has grown steadily in Maine ever since. Pfizer approached Northern Light about participating in the third round of clinical trials because Maine has one of the highest rates of Lyme in the country, Li said.

The clinical trial will take 13 months and include two shots two months apart, then a booster in March before next summer’s “peak season” for ticks, the doctor said. After participants receive the vaccine, Northern Light clinicians will assess its efficacy over two summers when the chances of people contracting Lyme are highest.

Participants cannot have been diagnosed with Lyme disease within three months of enrolling in the trial, or have been bitten by a tick within four weeks of the trial beginning, Li said. People with preexisting conditions such as rheumatoid arthritis, lupus, multiple sclerosis or other chronic pain are also ineligible because their conditions can interfere with the trial assessment.

Northern Light will release information on how patients can volunteer for the trial next month. Registration opens in July.

Northern Light was the sole Maine health care organization agency playing a role in the vaccine’s clinical trial as of Thursday, according to Li.

As of Tuesday, 414 cases of Lyme disease had been reported in Maine so far this year, according to state data. The state has averaged about 1,600 cases annually between 2016 and 2020, the most recent years for which data are available. Maine and Vermont have seen the largest jumps in Lyme disease infections in the nation since 1991, according to the U.S. Centers for Disease Control and Prevention.

Most cases of Lyme can be treated successfully with a few weeks of antibiotics, according to the CDC. If left untreated, the infection can spread to a person’s joints, heart and nervous system.

If the Pfizer-Valneva vaccine receives FDA licensing, it will be the first Lyme vaccine on the market in the U.S. in two decades.

SmithKline Beecham Biologicals, a Belgian pharmaceutical company, developed a Lyme disease vaccine for humans called LYMErix that the FDA licensed in 1998.

Clinical trials showed that the vaccine reduced Lyme infections in vaccinated adults by nearly 80 percent. However, reports of side effects such as arthritis were common following the vaccine’s release, and a class-action lawsuit against SmithKline Beecham accused the manufacturer of concealing potential risks.

The FDA found in 2001, after 1.4 million doses had been distributed, that vaccine recipients experienced arthritis at the same rate as non-recipients. However, the manufacturer voluntarily withdrew the vaccine from the market in 2002, citing insufficient consumer demand following negative press coverage on potential side effects, according to a 2007 article on the vaccine by a pair of researchers from Children’s Hospital Boston.

Pfizer and Valneva’s vaccine is the only Lyme disease vaccine candidate currently in development, according to Pfizer’s website.

In the first round of clinical trials, 246 healthy adults ages 18 to 65 received the vaccine. Pfizer reported it was “safe and well-tolerated across all doses and age groups tested” and “no serious adverse events were observed in any treatment group.” The vaccine is now in the second phase of clinical trials, which expanded the subject group to include pediatric patients ages 5 through 17.

Should the vaccine receive approval for widespread use, Li said it would allow Mainers to enjoy outdoor activities without the risk of being infected with Lyme. However, people should still check themselves for ticks after being outdoors because they can transmit other diseases.

Kathleen O'Brien is a reporter covering the Bangor area. Born and raised in Portland, she joined the Bangor Daily News in 2022 after working as a Bath-area reporter at The Times Record. She graduated from...