Why is COVID-19 rising in California during summer, and should people get the current vaccine or wait for the updated shot expected later this year?
COVID-19 is once again picking up across the United States, with California seeing a particularly clear rise in infections this summer. The latest increase is reinforcing a shift health officials have been watching for the past few years: COVID-19 is increasingly behaving like a summer illness rather than a virus that peaks mainly during the winter. ()
The rise is not being driven by the kind of widespread severe disease seen during earlier phases of the pandemic. Hospitalizations remain relatively low compared with previous major waves. But wastewater measurements, test positivity and other indicators show that the virus is circulating at higher levels, including in California.
California’s Summer COVID Wave is Becoming a Pattern
California has now seen COVID-19 activity rise through the summer for the second consecutive year. State data show infections beginning to climb in June, increasing sharply through July and continuing upward in August.
The Centers for Disease Control and Prevention says COVID-19 infections are growing or are likely growing in 43 states. California is also among a small group of states where wastewater activity is currently considered moderate or high.
That is a significant change from the earlier years of the pandemic, when winter was generally the period of greatest concern.
Health officials now expect the seasonal pattern to look different. California is forecasting lower COVID-19 activity this coming winter, while summer has emerged as the more prominent period of transmission.
COVID-19 Levels Rise Across the San Francisco Bay Area
The increase is particularly visible in the San Francisco Bay Area.
Wastewater data show elevated or rising COVID-19 levels in San Francisco, Marin County, Palo Alto, Sunnyvale and San Jose. San Francisco has also reported increases in positive tests and COVID-related hospitalizations.
Researchers are watching a heavily mutated variant known as BA.3.2, sometimes referred to as the “cicada” variant, which may be contributing to the current increase. The variant is being detected more frequently, although it is not yet clear how much of the summer rise can be attributed to it.
Despite the increase in infections, the Bay Area has not seen a comparable jump in hospitalizations. That may reflect stronger immunity from previous infections and vaccinations, as well as changes in the virus and the population’s exposure to it.
Should You Get a COVID-19 Vaccine Now or Wait for the Updated Shot?
The summer surge is also creating a timing question for people who have not received the current COVID-19 vaccine.
California health officials are advising people who skipped the 2025-26 vaccine not to automatically wait for the updated 2026-27 version expected later this year. The reason is straightforward: transmission is elevated now.
California Public Health Officer Dr. Erica Pan has urged people who remain unvaccinated with the current vaccine to consider getting it during the present surge rather than waiting for the next formulation.
Nationally, vaccine uptake remains low. Only about 18% of U.S. adults had received the 2025-26 COVID-19 vaccine as of February, according to CDC data reported by the San Francisco Chronicle.
The currently available vaccines were designed around earlier strains, including LP.8.1 and JN.1. The next vaccines are expected to target XFG, which is currently predominant in the United States. Existing vaccines can still provide protection against XFG even though they were not specifically formulated for it.
Why COVID is Shifting Toward Summer
The changing seasonal pattern does not mean COVID-19 has become predictable.
The virus continues to evolve, while immunity from previous infections and vaccinations declines over time. Changes in people’s behavior, indoor gatherings, travel and the emergence of new variants can also influence when transmission increases.
What has become clearer is that COVID-19 no longer follows the simple winter-surge pattern many people became accustomed to.
For California, the past two years suggest that summer may now be the period when residents need to pay closer attention to rising transmission. The state’s current experience, along with increases being reported elsewhere in the country, points to a virus that remains active even as its impact has become less disruptive than during the pandemic’s worst waves.
For people at higher risk of severe illness, the current rise is a reminder that COVID-19 has not disappeared. Wastewater levels can provide an early indication of increasing transmission, while hospitalizations offer a clearer picture of how much the surge is translating into serious disease.
The immediate picture is therefore mixed: COVID-19 is spreading more widely this summer, but the increase in infections has not produced a comparable return to the severe hospital burden seen during earlier waves.
References:
- Is there a summer COVID-19 surge this year? Yep, it’s ramping up again – (https://www.npr.org/2026/08/14/nx-s1-5927115/summer-vaccine-covid-19-surge)
Source-Medindia