Some experts believe that San Francisco is approaching herd immunity, which is a milestone in California's efforts to control the COVID-19 pandemic.
San Francisco has one of the highest vaccination rates in California, with 72% of residents receiving at least one dose. Another county in California—Marin County north of San Francisco—has a higher vaccination rate, where 75% of residents are at least partially vaccinated. The vaccination rates in San Francisco and Marin County are significantly higher than the 56% statewide vaccination rate.
Herd immunity, also known as community immunity, occurs when a large part of the general population is vaccinated or survives a previous infection. People who are not immune to diseases are indirectly protected by herd immunity.
There is no clear percentage that can achieve herd immunity to the coronavirus. It can only be tested when basically all restrictions are relaxed and officials observe whether the spread of the disease has increased.
Previous guesses about when to achieve herd immunity to the virus ranged from 70% to 85% of community members who are immune. Although the parameters for achieving herd immunity are ambiguous, approaching it by maximizing vaccination rates remains the primary goal of public health experts.