Pfizer and Valneva have ticked off another milestone in their Lyme disease vaccine program, showing that booster doses safely trigger immune responses in adolescents and younger children in a phase 2 clinical trial.
Since buying the rights to multivalent protein subunit vaccine VLA15 for $130 million upfront in 2020, Pfizer has worked with Valneva to guide the candidate through a series of data drops in both adults and children. The partners shared initial phase 2 data in people aged 5 to 17 years last year, encouraging them to include children in their pivotal study, and have now returned with updated results.
The latest readout covers what happened after participants in the phase 2 trial received booster shots. In the trial, participants received either two or three doses over six months for their primary vaccination course, followed by a booster shot or placebo in Month 18.
Participants developed antibodies against Lyme proteins after receiving their booster doses. Depending on whether a two- or three-dose primary course was given, the seroconversion rate was 95.3% or 94.6% for all outer surface protein A serotypes in all age groups.
Antibody titers were significantly higher after the booster shot than following the primary schedule. One month after the booster, Pfizer and Valneva saw 2.0- to 2.7-fold increases in antibody titers compared to the same period after the primary schedule. The increase is down on the 3.3- to 3.7-fold jump seen in the adult population. The safety and tolerability profile was consistent with previous studies.
Pfizer and Valneva are continuing to track participants in the phase 2 clinical trial and plan to administer another booster shot or placebo at Month 30 to assess the need for ongoing dosing. But the big test of the candidate will come from another study, namely the phase 3 trial that Pfizer and Valneva are running to support filings for approval on both sides of the Atlantic.
The study suffered a setback earlier this year when compliance failings at some study sites forced the collaborators to remove around half of the participants from the trial. The setback delayed the trial by one year, pushing back the targeted data for seeking approval from 2025 to 2026.