evidence: The effectiveness of the vaccines declined from about 92% to 80% in reducing cases, the study, which was published by the CDC, showed. [...] Another study, conducted by the Mayo Clinic, analyzed vaccine effectiveness for both the Pfizer and Moderna vaccines among more than 80,000 people across all ages using data through July 16, Walensky said, adding, "Like we saw in the New York data, vaccine effectiveness against infection declined over time." The Mayo Clinic study found that effectiveness fell from 76% to 42% among those who received the Pfizer vaccine and from 86% to 76% among those who received the Moderna vaccine. "These data are currently available on a pre-print server," Walensky said.