The coronavirus Delta strain is responsible for over 80% of new Covid-19 cases in the United States. This was stated by top U.S. infectious disease expert Anthony Fauci at a hearing in the U.S. Senate on July 20, according to Reuters.
Moreover, U.S. Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky said during the hearing that an average of 239 people per day have died in the United States over the past week, nearly 48% higher than the previous week.
However, the authorized vaccines remain more than 90% effective in preventing hospitalizations and deaths, according to Fauci.
"The CDC is reviewing data from multiple groups of vaccinated people to determine how long protection from COVID-19 shots lasts and will use that information to make a determination on the potential role of additional booster shots," the statement reads.
As it was reported earlier, Pfizer company had previously planned to announce the necessity for a third dose of the coronavirus vaccine. Studies have shown that a booster dose increases antibodies by 5-10 times.