Pfizer and Valneva have added another plank of evidence in support of their Lyme disease vaccine candidate, revealing antibody levels remained elevated six months after the completion of dosing in a phase 2 clinical trial.
The study randomized 585 people aged between 5 and 65 years to take a two- or three-dose course of the vaccine, VLA15, or placebo. Pfizer and Valneva reported immunogenicity and safety data from the clinical trial earlier this year and continued to track participants after the initial period to gather more information about the persistence of the antibody response.
Antibody levels fell over the six months of follow-up but remained above baseline. Durability was best in the 177 people who received the three-dose regimen. Across all age groups, the geometric mean fold rises compared to baseline were 1.9-fold and 3.2-fold for two serotypes of the bacterial infection.
Almost half, 81, of the subjects in the three-dose cohort were aged 5 years to 17 years. Antibody levels after six months were highest in the youngest subpopulation, 5 to 11 years, with rises against the two serotypes clocking in at 2.8-fold and 6.6-fold. Pfizer and Valneva said the six-month update is the first antibody persistence data on VLA15 in pediatric populations.
The update supports the decision to use the three-dose schedule in the phase 3 trial, which is assessing the effect of the vaccine on confirmed cases in Lyme disease season. With the season extending deeper into spring and fall as the climate changes, durability could be an important attribute for the vaccine if it comes to market.
Pfizer and Valneva are still some way off revealing data from the 18,000-subject, placebo-controlled phase 3 study. Enrollment in the trial got underway earlier this year, putting the partners on track to seek approval for the vaccine in 2025 if the data support submission. Pfizer and Valneva plan to start a second phase 3 trial to gather more safety data in children this month.