A third dose of the Pfizer-BioNTech vaccine significantly increased neutralizing antibody levels against SARS-CoV-2, the virus that causes COVID-19, according to new research. Pfizer, BioNTech, and University of Texas Medical Branch scientists tracked the immune response of participants in clinical trials for the vaccine. They found that neutralizing antibody levels, the key protective immunity, dropped significantly over seven to nine months after the two-dose vaccination. This drop of neutralizing antibody levels correlates to the observation...