We could be close to a first in decades: the development and adoption of a vaccine against tick-borne Lyme disease.

Summer is a time for enjoying the great outdoors, especially shaded grassy areas where you can lie down and enjoy the weather. But it’s also the time of the year where pesky yet very dangerous critters hide in that very grass: blacklegged ticks.

Not only is their bite highly yiky and these insects supremely annoying to remove, but they also carry a very dangerous pathogen they spread through bites that can cause Lyme disease. Although it can be treated with antibiotics if detected, some cases of Lyme disease are antibiotic resistant and others go undiagnosed. For these patients or for those whose infection goes untreated, the disease can cause severe symptoms, including loss of facial mobility.

The incidence of this infection is on the rise around the world, and having access to a vaccine against the disease could help dramatically lower its incidence and protect public health. Pfizer and the French pharmaceutical company Valneva are looking to bring just one such vaccine to the market.

No to Lyme

“With increasing global rates of Lyme disease, providing a new option for people to help protect themselves from the disease is more important,” Annaliesa Anderson, the head of vaccine development at Pfizer, said in a news release. “We’re really looking at something that’s a seasonal vaccine”.

The two companies are embarking on a late-stage pharmaceutical trial with 6,000 participants. This will test the vaccine’s ability to protect individuals from the disease and, if successful, could lead to the first approved inoculation option against Lyme since 2002. It would also be our only available such option: the previous vaccine, Lymerix, was pulled off the market by its producer due to poor sales, despite being hailed as a great advancement for public health.

Participants in this trial will include adults and children aged 5 and older. These will be recruited among 50 sites where Lyme disease is endemic, such as Finland, Germany, the Netherlands, Poland, Sweden, and the United States. Each will receive three doses of the vaccine candidate VLA15 or a placebo, followed by one booster shot or another placebo.

Small, early-stage studies showed no safety problems caused by the vaccine candidate, and that it produces a good immune response in participants. If successful, the current trials would pave the way for the vaccine to be approved by regulators in both Europe and the U.S. by 2025.

Today, cases of Lyme disease have been recorded throughout all U.S. states, with about 476,000 of its citizens receiving treatment for the disease annually, according to the CDC.

Early symptoms of this include rashes, fever, chills, headache, fatigue, muscle, and joint aches, as well as swollen lymph nodes. If detected, the disease can be treated rapidly and quite effectively with antibiotics. Despite this, infections can result in permanent damage to joints or cause facial palsy, or drooping. Between 10 and 20% of treated patients still experience joint pains, memory problems, and tiredness for at least six months. Around 1% of cases can lead to Lyme carditis, caused by the bacteria reaching the heart. And although rare, Lyme can be fatal — the CDC explains that 11 fatal cases of Lyme carditis were reported between 1985 and 2019.

The disease spreads through the bite of black-legged ticks. These insects burrow head-first into the skin in hard-to-see areas such as the groin, armpits, or scalp. Although the bacteria is transmitted through their bites, a tick must stay attached to the body for 36 to 48 hours or more before the bacteria can be transmitted. There is no data to show that it can then spread from person to person or from pets to individuals — although pets can bring ticks carrying the pathogen into the yard or home.

Lyme disease is a growing problem. Warming climates are allowing ticks to expand their habitat and cases are surging as a result. Veterinary vaccines against Lyme are already in use, but so far, people must rely on bug spray and their own vigilance to ward off ticks.

The Pfizer study will span two tick seasons. Meanwhile, University of Massachusetts scientists are also working on a vaccine alternative, shots of pre-made Lyme-fighting antibodies.