Protesters are reportedly calling for Golden Gate Fields' race track to be shut down, citing dozens of horse deaths over the past year as well as widespread COVID-19 outbreaks among workers at the track.
The protesters were seen locked together between PVC pipes, lighting flares that sent purple smoke into the sky.
VIDEO: SKY7 over horse racing protests at Golden Gate Fields
Golden Gate Fields released a statement saying: "Golden Gate Fields is a firm believer in the right to protest. However, the current actions of the protesters have forced the closure of the onsite COVID vaccination clinic, and hundreds of people have already had their vaccinations canceled."
A spokesperson for the City of Berkeley estimated about 200 appointments will have to be rescheduled.
The site was closed for three hours as Albany Police assessed the safety of the vaccination site, according to Captain Colin Arnold with the Berkeley Fire Department which helps run the site.
"The recommendation from Albany Police was that we close down the site out of an abundance of caution until they could figure out what was going on," said Arnold.
While four activists made it onto the track, Arnold said the rest of the group was on the other side of the facility and never got closer than 300 yards from where the vaccinations were occurring.
Albany City Councilmember Aaron Tiedemann said he came down after he heard the vaccinations had been paused due to a protest.
"I figured it must be a big one, I was surprised it was smaller than I expected," he said.
He had not been in contact with Albany Police but said he would be reaching out to get more information on the decision.
"I'm hoping to find out exactly why we couldn't keep the vaccination site running while we had this going," he said, pointing to the small group of protesters outside the facility.
"We're locked down on the track today in order to prevent any more horse deaths. 5 horses have been killed at Golden Gate Fields this year," said Samantha Eachus, a member of the group Direct Action Everywhere.
She said they intended to stop races at the track but did not expect their protest would disrupt the vaccination event.
"The choice to shut down the vaccination site is entirely within the Albany Police Department and the Golden Gate Fields Track," she said.
Protester Almira Tanner said she felt sorry for the people who missed their vaccine appointment, but deflected blame to Albany Police.
"We pose no hazard to the vaccination site," she argued. "But I encourage them to submit complaints to the Albany Police Department," she said.
The Albany Police Department did not respond to requests for comment.
According to their Twitter account, Golden Gate Fields resumed races at 7 p.m.