SAN FRANCISCO (CBS SF) — Ahead of the state’s official reopening on June 15, San Francisco has a reached milestone in COVID vaccine immunizations.

Mayor London Breed announced San Francisco is the first major American city with 80% of eligible residents having received a vaccine dose.

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San Francisco may be one of the first major cities to reach herd immunity. According to the San Francisco Department of Health COVID dashboard, the city is seeing only about 12 to 13 new cases a day.

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Many health experts believe the percentage of vaccinated needed to reach herd immunity has bumped up to 80-to-90 percent, a threshold some believe San Francisco has reached partly because of the high rate of infection during the winter.