A Lyme-disease vaccine candidate produced antibodies that lasted at least six months.
The vaccine is being created by the French biotech company Valneva in partnership with Pfizer.
If Pfizer and Valneva's vaccine gets approval, it'll be the first of its kind available in 20 years.
Valneva, a French vaccine maker, and Pfizer said Thursday in a follow-up to a phase 2 safety trial that the companies' vaccine candidate for Lyme disease had produced lasting immunity.
The phase 2 trial was completed in April, and six months later, the companies checked the antibody levels of children and adults who received either two or three shots of the vaccine. The companies found that antibody levels remained higher in the three-shot group compared with the two-shot group.
While these antibody levels did fall over time, they indicated some level of lasting protection against Lyme disease. The companies didn't report any serious side effects or safety problems and are now in the middle of phase 3 clinical trials.
Lyme disease is a bacterial illness spread by tick bites. The hallmark symptom is a rash resembling a bull's-eye around the bitten area, but symptoms can also include fever, chills, joint pain, and headache. If it isn't treated quickly, it can cause carditis - swelling of the heart - or arthritis. Some people can continue to have symptoms for a long time after treatment, a condition called post-treatment Lyme-disease syndrome.
A Lyme vaccine was pulled from the market 20 years ago
There's already been one US Food and Drug Administration-approved vaccine for Lyme disease. GSK - then called SmithKline Beecham - made a Lyme vaccine that was approved by the FDA in 1998. Called Lymerix, it was about 75% effective at preventing Lyme after three shots.
But at the time, the Centers for Disease Control and Prevention rarely recommended the vaccine because the disease was seen as easily treatable in early stages. In addition, patients were reluctant to take the vaccine because they found the dosage schedule inconvenient, and it was not approved for children because it had not been tested in that population.
It was removed from the market in 2002 after patients said it caused severe side effects like arthritis and filed a class-action lawsuit. The CDC and FDA didn't find a pattern with the vaccine causing these reactions, but this didn't save Lymerix. Sales fell so dramatically that GSK withdrew the drug from the market.
Valneva and Pfizer are hoping that the new Lyme vaccine gets a better public reception. If the phase 3 study results are positive, the companies are aiming to get FDA approval for the vaccine in 2025.
Lyme disease is a growing problem
Lyme disease has become much more of a concern since 2002. According to the CDC, about 30,000 cases are reported each year, though the agency says this is probably lower than the true number of cases because of undercounting. This is compared with about 24,000 cases that were reported in 2002. A study using private insurance-claims data estimated that about 476,000 patients were diagnosed with and treated for Lyme disease between 2010 and 2018.
In 2022, a study estimated that 15% of the global population had contracted Lyme disease at some point in their lifetimes.
One theory for increasing Lyme prevalence in the American Northeast involves the rise of patchy forests, which leads to more of a particular kind of mouse that's a great reservoir for Lyme-causing bacteria. Additionally, the climate crisis is expanding the range of disease-carrying ticks because warmer temperatures can speed up the life cycle of ticks and make winters more survivable.