SACRAMENTO (CBS13) — The COVID-19 vaccine has been widely available for about a month.

State leaders are collecting data that shows the percentage of people who are fully vaccinated by zip code, revealing cities that are building immunity faster than others. But does that mean those communities are safer?

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According to the state’s vaccine data map, in one Rancho Cordova neighborhood, about 63% of people are fully vaccinated. Good progress, doctors say, but not on a big enough scale.

“I think there’s enough mixing around, that it’s not just by zip code, that we can really achieve that herd immunity,” said Dr. Dean Blumberg with UC Davis Health.

People live, work and shop all over the place.

Dr. Blumberg said a population needs to be at least 75% vaccinated to really limit COVID-19 transmission and create herd immunity. So could a city achieve that?

“The answer is ‘kind of.’ You can’t really be definitive about that,” Dr. Blumberg said.

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At the very least, people living in cities with high rates of full vaccination would be safer. Elk Grove Mayor Bobbie Singh-Allen said that’s what keeps her motivated.

“We have the largest school district in Northern California here,” she said.

According to state data, Elk Grove is about 46% fully vaccinated. For comparison, nearby West Sacramento is at 34% and Lincoln is close to 60%.

“The more vaccination there is within the city, then it’s going to be safer for everybody there. People who live there and people who visit there,” Dr. Blumberg said.

Mayor Singh-Allen said success in one city like Elk Grove depends on people in the entire county getting fully vaccinated.

“This is also a plea to the rest of the county we must really get our messages out there, particularly to low-income families and our communities of color,” she said.

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Dr. Blumberg said the one wildcard with all of this is the variants that have been spreading. They are highly transmissible and even large populations of vaccinated people wouldn’t fight them off as easily.