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A new shot to prevent Lyme disease is being tested in human trials and could be available within the next two years, according to a doctor involved in its development.

"We're getting there," Dr. Mark Klempner, who is working on the shot at MassBiologics, a nonprofit unit of the University of Massachusetts Medical School, told WBUR-Radio.

Lyme disease, a bacterial infection spread by certain ticks, is the most common illness in the U.S. transmitted by the bite of an infected insect.

Klempner said it "would not be out of the question" to see the shot distributed as soon as 2023.

The shot isn't a vaccine that triggers the immune system to make antibodies. Instead, it delivers the anti-Lyme antibody directly to the patient, Klempner wrote in an article for The Conversation. The process, known as Lyme PrEP, blocks the bacteria that cause the disease from entering the human body.

"Unlike a vaccine, Lyme PrEP uses a single human antibody, or blood protein, to kill the bacteria in the tick’s gut while it takes its blood drink, before the bacteria can get into the human host," Klempner said.

A new shot to prevent Lyme disease is being tested in human trials and could be available within the next two years, according to a doctor involved in its development.

"We're getting there," Dr. Mark Klempner, who is working on the shot at MassBiologics, a nonprofit unit of the University of Massachusetts Medical School, told WBUR-Radio.

Lyme disease, a bacterial infection spread by certain ticks, is the most common illness in the U.S. transmitted by the bite of an infected insect.

Klempner said it "would not be out of the question" to see the shot distributed as soon as 2023.

The shot isn't a vaccine that triggers the immune system to make antibodies. Instead, it delivers the anti-Lyme antibody directly to the patient, Klempner wrote in an article for The Conversation. The process, known as Lyme PrEP, blocks the bacteria that cause the disease from entering the human body.

"Unlike a vaccine, Lyme PrEP uses a single human antibody, or blood protein, to kill the bacteria in the tick’s gut while it takes its blood drink, before the bacteria can get into the human host," Klempner said.

It's designed to be a seasonal shot that people would get once a year before tick season.

Ticks are most active and most Lyme disease infections occur from May through August, with June and July being the peak months.

Clinical trials in humans started in February with 66 people, according to WBUR. Initial testing is expected to last the rest of the year to make sure that the antibodies stand up through an entire tick season. Further testing for the shot's effectiveness could start next year.

The shot isn't the only technique in development to prevent Lyme disease. Valneva, a French company, and Pfizer are conducting human trials of a vaccine, according to the U.S. Centers for Disease Control and Prevention.

The CDC says a previous vaccine was withdrawn from the market in 2002 due to lack of demand. Patients complained of side effects and some sued the vaccine maker, The New York Times reported.

Experts believe warmer and wetter winters are to blame for rising numbers of Lyme disease in recent years. The disease is heavily influenced by the weather, especially temperature, precipitation, and humidity.

Changing weather patterns also mean ticks are showing up in new geographical areas where more people might be exposed to them.

A CDC study released in January estimated that as many as 476,000 people nationwide are diagnosed with Lyme disease each year, a number far higher than the 35,000 or so that are typically reported to the agency by state health departments.

The CDC came up with the number after reviewing billing codes on health insurance claims from 2010 to 2018. While the agency notes the numbers are just an estimate, the number of actual cases reported to the CDC has risen in recent years.

Initial symptoms of Lyme disease can include fever, chills, headache, fatigue, muscle aches, and swollen lymph nodes. A bright red rash resembling a bullseye is a tell-tale sign of the disease. Later, patients might develop severe headaches and muscle stiffness, drooping on one side of the face, nerve pain, and pain in muscles, joints, bones, and tendons. More severe complications include heart palpitations and chest pain.