Riverside County aims for COVID-19 herd immunity by mid-June

A health worker measures a dose of the Moderna vaccine.
A health worker measures a dose of the Moderna vaccine at a vaccination site in the parking lot of the Riverside Convention Center in February.
(Gina Ferazzi / Los Angeles Times)

Riverside County could reach herd immunity against COVID-19 before June 15, the date California is aiming to fully reopen its economy, public health officials said.

“We do believe we have the capacity and the vaccine supply to be able to do that,” Public Health Officer Dr. Geoffrey Leung said at a Board of Supervisors meeting this week.

Herd immunity occurs when enough of a population is immune to an infectious disease that it is unable to spread readily. That provides an indirect form of protection to those who can’t be vaccinated. It’s usually achieved through vaccination but also can occur through natural infection.

Reaching that critical juncture in Riverside County will likely occur by administering as many vaccines as possible over the next eight to 10 weeks, Leung said.


“We do believe vaccination is the easiest way for us to return to a more normal life,” Leung said, referring to school and workplace reopenings.

The county’s optimistic prediction arrived Tuesday, just after California announced it would pause the use of the Johnson & Johnson vaccine at the recommendation of federal health officials. The decision followed reports of six serious blood clots in women nationwide. One woman died and another was hospitalized in critical condition.

Nearly 1.3 million doses of all vaccines — J&J, Moderna and Pfizer-BioNTech — had been administered across Riverside County as of Tuesday, according to Kim Saruwatari, the county’s director of public health. About one in three residents have received at least one dose, Leung said.

Reaching that milestone “would dramatically change the trajectory of the pandemic,” Public Health Director Barbara Ferrer said

Just under 53% of county residents 65 and older are fully vaccinated, and 69% have received at least one dose. Roughly 22% of those 16 and older are fully vaccinated, and nearly 39% are at the halfway mark.

On Thursday, all Californians 16 and older became eligible for the vaccine.

Other parts of the state are making strides in their vaccination efforts, as well. Los Angeles County officials said they could hit an 80% vaccination rate for residents 16 and older by the end of June — if supply holds up.

“Reaching such a milestone is possible with increased allocations, and it would dramatically change the trajectory of the pandemic here in L.A. County,” Public Health Director Barbara Ferrer said during a briefing in late March.

That’s good news for places like Riverside County. According to Leung, residents will likely still need to rely on masks until case rates drop statewide and nationally.

Herd immunity, however, could make a large immediate impact on local gatherings as well as capacity for indoor and outdoor events.

“When you have individuals that are fully vaccinated, that are together, that’s really considered a safe environment,” Leung said.