evidence: They cited three new studies, released by the Centers for Disease Control and Prevention, that showed their protection against Covid diminished over several months. One study in New York from May 3 through July 25 showed that vaccine protection against infection dropped from around 92% to 80%. Another study by the Mayo Clinic showed that Pfizer's vaccine efficacy fell from around 76% to 42% while Moderna's declined from 86% to 76%. "Taken together, you can see that while the exact percentage of vaccine effectiveness over time differs depending on the cohort and settings study, the data consistently demonstrate a reduction of vaccine effectiveness against infection over time," Walensky told reporters during a White House Covid press briefing. [...] Israel, a country U.S. officials have also cited in their push for boosters, has begun giving out third doses to the elderly after new data showed a reduction in the effectiveness of Pfizer's Covid vaccine against severe illness among people 65 and older who were fully vaccinated in January or February.