There are still a few unknowns, and it would be unwise to declare ourselves definitively out of the woods, but some often-quoted experts at UCSF are sounding pretty bullish about San Francisco's shot at herd immunity.

If the city can inoculate enough teens, tweens, and remaining reluctant adults in the next three weeks, herd immunity for the city may be possible, the epidemiologists say. This would make San Francisco the first California city to even approach this ever-elusive remission point for the pandemic.

"I'd say it's pretty close," says UCSF epidemiologist Dr. George Rutherford, speaking with ABC 7.

As of Monday, 624,528 San Franciscans had received at least one vaccine shot — that represents 79% of all city residents age 12 and up. 68% of residents have completed a vaccine series or received the one-dose Johnson & Johnson shot.

There have been a lot of mixed messages about herd immunity with this virus and whether it is even possible at the national level, given Americans' slow overall uptake with vaccinations. The answer seems to be no, that nationwide there will be no such broad safety, and unvaccinated people are going to keep getting infected and dying until the message finally gets through to them.

Experts believe that it may take 90% or even 95% of eligible people to get vaccinated (or to have been previously infected) to achieve herd immunity — at which point there are not enough people to infect let alone spread the virus if comes into the city from elsewhere.

But on the local level, herd immunity has always been possible, though we need the rest of the Bay Area to catch up to San Francisco and Marin counties in vaccination rates for this to work.

Rutherford and Dr. Monica Gandhi seem to agree that California might reach herd immunity as a state by September, if schoolkids continue to get vaccinated at a decent rate all summer and a greater dent is made in vaccine uptake in counties that have shown the most reluctance.

And, Gandhi says to ABC 7, we don't yet know what a herd immunity percentage is for COVID-19, and it's something that will need to be tested in a real-world setting, when masks come off, i.e. after June 15.

"There will be more mingling, there will be people around each other, we're going to watch those cases very carefully and if they don't go up which I suspect they won't, that's when you say, yeah, we've gotten to herd immunity," Dr. Gandhi says. "You have to test it with human interaction within the population."

We'll have to wait a week or more to see if the state's $116.5 million lottery ploy ends up netting some higher vaccine numbers.

In Los Angeles County, where mass-vaccination efforts seemed largely successful, 53% of the eligible population is now fully vaccinated. In San Diego County, it's 50%.