Emerging COVID 'Cicada' Subvariant Detected Across California as Experts Warn of Low Senior Vaccination Rates

A new strain of the coronavirus, scientifically designated as BA.3.2 and informally known as the “Cicada” subvariant, is now circulating in California, public health officials have confirmed. As of spring 2025, the strain has appeared in state wastewater samples and is being monitored for potential impacts on COVID-19 transmission as summer approaches.

The Cicada subvariant stands out due to its high number of mutations and ability to evade immunity from previous infection or vaccination, according to research published by the U.S. Centers for Disease Control and Prevention (CDC). While the statewide prevalence is currently low—comprising about 5% of U.S. wastewater samples in late March according to Stanford University scientists—experts caution that even a modest rise in circulation could pose additional risks, especially among older adults.

California has experienced stronger COVID-19 waves during recent summers compared to winters, diverging from the pattern seen earlier in the pandemic. State health data show that the 2024 and 2025 summer peaks outpaced winter surges, while influenza dominated among respiratory diseases during the last two winters.

Concerns are heightened by lagging COVID-19 vaccination rates among seniors. Only 28.7% of Californians aged 65 and older have received a dose of the updated vaccine released in September, according to the California Department of Public Health. Authorities continue to recommend updated vaccinations for everyone aged six months and older, with special emphasis on those at risk of severe illness such as older adults, pregnant women, young children, healthcare workers, and residents of long-term care facilities.

First detected in South Africa in November 2024, the Cicada subvariant was identified in the U.S. by June 2025, initially in a sample from an international traveler at San Francisco International Airport. The strain has since been reported in at least 23 countries and in roughly a third of surging coronavirus cases in parts of Europe in the past year.

Despite its increased ability to bypass immunity, current monitoring indicates that the Cicada subvariant has not triggered more severe illness or a major spike in cases in California. Wastewater concentrations of the virus remain relatively low, and experts do not anticipate the variant becoming dominant. California officials project only a modest wave of COVID-19 may materialize in late summer or early fall, but emphasize that the situation warrants close observation.

Health experts urge seniors and others at risk to get vaccinated if they have not done so within the last year, noting that COVID-19 continues to pose a significant risk of hospitalization, death, and complications such as long COVID. Authorities stress that vigilance remains necessary, even amid quieter winter seasons, as variant trends and immunity gaps can shift the pattern of outbreaks.