COVID-19 Surge in California Driven by New ‘Stratus’ Variant Linked to Omicron

Rising Cases and Hospitalizations

COVID-19 cases are climbing in California, with public health officials noting a significant uptick in Los Angeles and Santa Clara counties. Wastewater surveillance shows increased coronavirus levels, and Los Angeles County has reported a slight rise in COVID-related hospitalizations. For the week ending August 16, 2025, L.A. County’s test positivity rate reached 12.6%, up from 7.6% a month prior, while Orange County’s rate hit 14.4%, up from 8.1%.

Dr. Elizabeth Hudson, regional infectious disease chief at Kaiser Permanente Southern California, noted an increase in outpatient cases, particularly as the back-to-school season drives infections, including among children. Dr. Matt Willis, former Marin County health officer, stated that California’s COVID-19 rates are among the highest in the U.S., with the Southwest region reporting a 12.5% positivity rate, the nation’s highest.

The Stratus Subvariant

The surge is largely attributed to the XFG subvariant, dubbed “Stratus,” an Omicron offshoot dominating wastewater samples. Dr. Hudson explained that prior Omicron infections may provide some protection, but reinfections remain possible. Despite the rise, this summer’s wave is less severe than last year’s, with L.A. County hospitalizations at half the level of August 2024 and Orange County emergency room visits for COVID-like illness significantly lower than last summer.

Vaccine Delays and Policy Shifts

The Trump administration’s policies have delayed the rollout of updated COVID-19 vaccines for fall 2025. Unlike previous years, when vaccines were approved by June for a September rollout, decisions under Health and Human Services Secretary Robert F. Kennedy Jr., a vaccine skeptic, have created uncertainty. The FDA may further restrict eligibility for the updated shots, though current evidence supports their safety and efficacy across all ages. The California Department of Public Health warned that vaccine availability may be limited and delayed due to federal indecision.

Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, described the delay as “unusual,” urging high-risk individuals—those over 65, immunocompromised, pregnant, or infants aged 6 to 23 months—to get vaccinated now if they haven’t in over a year. He noted that the 2025-2026 vaccine formula is similar to last year’s, making immediate vaccination a practical choice.

Diverging Recommendations

The federal government’s stance, influenced by Kennedy’s skepticism of mRNA vaccines, has led to significant changes. Kennedy dismissed all 17 members of the CDC’s vaccine advisory committee and appointed a vaccine critic to lead a safety review. The CDC now advises parents to consult healthcare providers before vaccinating healthy children, a step that could hinder access. It also provided no guidance on vaccinating healthy pregnant women.

In contrast, the American Academy of Pediatrics recommends updated COVID-19 vaccines for infants and children aged 6 months to 23 months, citing their high risk. It also supports offering the vaccine to children over 2 at parental discretion. The American College of Obstetricians and Gynecologists recommends vaccination for pregnant, postpartum, or lactating individuals, citing reduced risks of severe complications, preterm birth, and stillbirth.

Public Health Challenges

The conflicting guidance between federal agencies and medical organizations has created confusion. Orange County’s health officials noted that navigating these differences will be challenging for the public. Despite the less intense summer wave, the rise in cases, driven by the Stratus variant and compounded by vaccine delays, underscores the ongoing need for vigilance as California grapples with this evolving public health challenge.