If you're signing up to get the COVID-19 vaccine in Santa Clara County, chances are you're headed to San Jose. That's because smaller vaccination centers elsewhere in the county, including Mountain View, are still overloaded and fully booked with appointments through this week.

Santa Clara County health officials have shifted gears over the last month from having pent-up demand and too few vaccines to an abundance of shots and not enough people showing up. The reversal has fueled concerns that younger residents and those reluctant to get the vaccine may not get vaccinated, threatening the county's goal of reaching herd immunity.

Yet perplexingly, that abundance doesn't appear to be reaching all county vaccination sites. At a Health and Hospital Committee meeting Wednesday, county Supervisor Joe Simitian said he was told by county health officials more than once not to encourage people to get a vaccine from the Mountain View site and instead seek a shot from other facilities.

Simitian noted that the alternative sites are hardly convenient for North County residents, with 11 of the 13 sites taking new appointments located in San Jose. The other two were located in Gilroy and Sunnyvale.

"I am concerned, frankly, that we have folks who both need to get the vaccine and are willing to get the vaccine if we would only make it easy for them to do that," Simitian said. "And by not having a walk-in facility available these last few weeks, we have lost an opportunity."

The county converted the Mountain View Community Center on Rengstorff Avenue into a mass vaccination site in late January, making it one of the first county-operated sites north of Santa Clara. Hastily renovated in a partnership with the city of Mountain View, the site is capable of providing up to 1,000 vaccinations per day.

County Health Officer Sara Cody said the Mountain View site has been at full capacity for the last few weeks due to a combination of second-dose appointments and a surge in first-dose appointments for teens who are now newly eligible to receive the Pfizer vaccine. She said the site's capacity is constrained by limited parking and other factors that make it tough to scale up, which is why most residents seeking an appointment are going to be directed elsewhere.

The good news, Cody said, is that the site will have drop-in appointments available starting Monday.

Despite the assurances, Simitian said he was concerned that the Mountain View site -- a convenient location for North County residents -- is being under-used and could ramp up appointments. He insisted that close and easy-to-access vaccination sites are a crucial way to encourage those who are hesitant or indifferent about getting the vaccine to finally get the shot.

"I understand the concerns about parking, but it's a global pandemic -- at some point we need to be clear about priorities," Simitian said. "I want to make sure if the site has the capacity to provide more shots over the last couple of months that we not scale it down."