President Joe Biden’s goal of having 70 percent of American adults vaccinated against the virus that causes COVID-19 by July 4 is not the same as the threshold for herd immunity, the director of the Centers for Disease Control and Prevention said Thursday. “We know that the more and more people who get one vaccine and then two, get fully vaccinated, the more we as a nation are protected,” Dr. Rochelle Walensky, the director, said during an appearance on NBC’s “Today” show. “We know that the vaccine not only protects individuals, it protects communities, it protects their families, and so the more people who get vaccinated—as we all have talked about, there is no magic target for the herd immunity—but we believe that getting to 70 percent would go an extraordinarily long way to making sure we have community protection,” she added. Herd immunity refers to reaching immunity in a …