Happy New Year! I hope everyone had a restful, if wet, holiday break. 2026 has started with bang for us in public health. We’re facing radical changes to federal vaccine policy, flooding from winter storms, and surges in seasonal viruses. Let’s start with flooding.
Flooding in California: Health impacts
We’ve had a very wet start to the new year in California, with atmospheric rivers, heavy rain, saturated ground, and king tides pushing water onto streets and into neighborhoods. The National Weather Service has already issued multiple flood advisories statewide in 2026.
I saw this play out close to our home in Marin County a few days ago. Highway 101 was closed for hours as heavy rain runoff met high tides. Some neighbors experienced flooding of homes and garages; we live up a hill and were spared. That uneven, block-by-block impact is common during flood events.
What happened in Marin isn’t isolated. More than 7 million Californians—about 1 in 5 of us—live in areas at risk of flooding from rivers, stormwater, or along the coastline. And climate change is amplifying that risk: climate models show flood risk increasing as storms become more intense and sea levels rise.
Slow, shallow flooding is often treated as an inconvenience more than a health risk. Water can rise with high tides or heavy rain, linger in streets and buildings, and then recede. When that happens, the health impacts may be less obvious—but they’re real. Here are the health issues we see most often with coastal flooding—and what you can do to protect yourself and the people you care about.
Contact with contaminated water. Floodwaters can carry sewage, agricultural runoff, and chemicals when storm drains and wastewater systems are overwhelmed. This is why after major floods, incidence of gastrointestinal illnesses rise.
Avoid contact with standing floodwater when possible.
If cleanup is necessary, wear gloves/boots and wash thoroughly afterward.
Follow boil-water advisories, and test private wells if flooding occurred nearby.
Mold and respiratory problems. When water enters buildings, mold can start to grow within 24–48 hours and persist for weeks, contributing to asthma flare-ups and respiratory symptoms, especially in children and people with lung disease. Rapid drying and removal of wet materials reduces risk.
Dry flooded areas quickly with fans and dehumidifiers.
Remove water-soaked materials that can’t be fully dried.
Use an N95 type mask during cleanup if respiratory issues are present.
Traffic injuries and drownings. A leading cause of flood-related injury and death is when people drive into rising waters and lose control of their vehicle or are swept off roads.
Never drive through flooded roads: “Turn around, don’t drown.”
Avoid unnecessary travel during and immediately after heavy rain or tide events.
Disruptions in care for chronic conditions. Flooding can interrupt access to medications, dialysis, oxygen, or refrigerated insulin, particularly when roads are closed or power is out. Recent studies show these factors are major contributors to hospitalizations and mortality during and after floods.
Keep at least a 7-day supply of medications on hand during storm seasons.
If you depend on electrically powered medical equipment, register with your utility provider’s priority power program. Here are links to programs at San Diego Gas and Electric, Southern California Edison, and Pacific Gas and Electric.
Stress and mental health strain. Flooding is stressful—not just while waters rise, but in the recovery that follows. Anxiety, sleep disruption, and symptoms of depression often emerge after flood events, particularly for those with property damage or repeated exposures. There’s abundant research showing that community connection improves disaster recovery and resilience.
Check in on neighbors, especially older adults.
Consider joining California Volunteers—a community-focused initiative in California that encourages neighbors to connect, prepare, and check in on each other before or during disasters.
Use resources like 988 in California for mental health support if distress persists.
Stay informed. One of the simplest ways to reduce flood harm is timely information. The National Weather Service Flood & Coastal Alerts and California Emergency Alerts provide alerts, advisories and real time updates. Check your city and county websites to sign up for local emergency alert systems—Nixle and Everbridge are common platforms.
Infectious disease “weather report”
As we head deeper into winter, the latest numbers show what many of us are already feeling: flu is seriously picking up across California.
Flu. Over the month of December, all state level indicators of flu activity increased dramatically. Emergency department visits jumped ten fold, hospitals increased five fold, and we saw our first pediatric influenza death in California.
Wastewater concentrations continue to rise, meaning that flu transmission is still increasing in our communities. We should expect upward trends in serious outcomes to continue through January.
The most recent national data shows that about 80 percent of flu cases are subclade K of the type A H3N2 flu strain. This variant is similar in severity to other common seasonal strains. In England, where the virus hit months ago, the vaccine was 70-75% effective at preventing hospitalization in children, and 30-40% effective for adults. Current flu treatments like Tamiflu also protect against serious outcomes in subclade K infections.
RSV activity is increasing across California, with the highest impact among children. Pediatric hospitalizations for RSV and flu are rising quickly, and at similar rates.
Covid rates remain at low levels statewide.
What this means for you
We’re in the thick of virus season. Masking up in crowded indoor places can help prevent infection.
If you’re sick, stay home. A flu test can help diagnose illness early enough to benefit from treatment— antivirals like oseltamivir (Tamiflu) can shorten duration of illness if started within a couple days of symptom onset.
Importantly, it’s not too late to get vaccinated! Vaccines are available across California. You can visit MyTurn to schedule a shot today.
Childhood vaccines schedule changes: What California parents should know
In my last post, “We’re not Denmark,” I described why the U.S. shouldn’t import vaccine policy wholesale from countries like Denmark that have universal health care, different disease prevalence, and fewer health care access barriers.
On Monday, federal health leadership announced they were doing just that: a radical and unprecedented change to adopt a childhood vaccine schedule similar to that of Denmark. Six of the 17 vaccines that had long been universally recommended for all children in the U.S., including flu, Covid-19, hepatitis A and B, RSV, rotavirus, and meningococcal disease, were moved into new categories such as “high-risk only” or “shared clinical decision-making.” Katelyn at YLE National offered an analysis of the new federal changes on Tuesday.
What this means for us in California
I want to hold two things at once. Yes, this decision is deeply troubling. This change wasn’t prompted by any new data or emerging scientific consensus. It was a unilateral, top-down decision that bypassed the usual advisory process to review evidence, weigh risks and benefits, and update recommendations transparently. There was no opportunity for public comment.
It undermines decades of evidence-based policymaking, weakens national coordination, and injects ambiguity into a system where clarity matters. This is how gaps open—and how preventable outbreaks happen. But it’s also important to recognize the limits of federal control in times like these.
For California families, this won’t impact our access to vaccines directly. California’s response has been steady, clear, and stabilizing. Our doctors and nurses still recommend routine childhood immunizations for all 17 diseases on the prior vaccine schedule, based on the same evidence that has guided care for decades. This week, medical societies and the West Coast Health Alliance were quick to reaffirm their commitment to those standards.
Shared decision-making
As a doctor, I find it especially misleading that RFK’s team is framing shared decision-making as a new concept. I always approached vaccines as an open conversation with patients. Despite the rhetoric, no new vaccine schedule was needed to give parents a voice in decisions about their children’s health. Vaccine decisions for your kids should always be made in partnership with your health care provider, in conversations grounded in evidence and trust.
The new recommendations don’t change that for patients. For providers, it’s a good reminder that we need to do a better job of having these conversations, especially as families get more confusing information.
Here’s what parents should know—and how to navigate this moment with clarity, not fear.
What parents should do now
Stick with your child’s recommended vaccine schedule still endorsed by the American Academy of Pediatrics and the California Department of Public Health. The science hasn’t changed, and California clinicians continue to recommend routine childhood immunizations.
Talk with your pediatrician—and ask questions. If you’re unsure about timing, risks, or benefits, your child’s clinician will help you weigh them based on your family’s circumstances. Pediatricians welcome questions and discussion—that’s part of their job, and it always has been.
Know that insurance coverage for vaccines hasn’t changed. In September California passed a law requiring insurers to cover all vaccines recommended by the California Department of Public Health, as a proactive step to protect our access when federal systems falter. And as another layer of reassurance, this week’s HHS announcement specifies that insurers must cover vaccines for the full 17 diseases on the prior vaccine schedule, at least through 2026.
Know that school requirements haven’t changed. States set their own school-entry vaccine requirements. California children will still be required by state law to be up to date with required vaccines before starting kindergarten, or have a medical exemption.
If your child is behind on vaccines, it’s not too late. Catch-up schedules are safe, effective, and commonly used—especially after disruptions from illness, moves, or the pandemic.
Bottom line
Stay out of floodwater. It’s not too late to get a flu shot. And follow the evidence-based vaccine guidance provided by your clinician and our regional public health leaders. We’ll see you next week.
Love,
Matt
Dr. Matt Willis is the author of Your Local Epidemiologist in California. A California native, he’s served as a primary care physician, CDC epidemiologist, and public health officer for Marin County, where he guided the pandemic response. He lives in Marin with his wife, children, and their dogs Teddy and Ramona.
Speaking as a family doc and public health epidemiologist, I find it to be subversive and dysfunctional to apply "shared decision making" to immunization policy. I hope you will discuss this in detail in future posts.
(1) "Informed consent" is always appropriate and the ubiquitous VIF forms and the attendant discussions have contributed greatly to educating families.
(2) "Shared decision making" is a concept beyond informed consent deviously borrowed from clinical medicine (not a public health concept) which is best applied to an individual ill patient's specific clinical circumstances where RX choices are unclear, multiple, risky, of concern to the patient or uncertain.
(3) In fact, as vaccines are intended to be given to healthy people and large populations, they must undergo heightened evaluation for safety. In fact this has been and has been an ongoing process for all vaccines in use. This has led to the (much criticized) delay for COVID vaccines for pregnant women and the discontinuation of some vaccine formulations. Current HHS policy makers have ignored all the evidence in this regard while providing distorted (mis)information. It has been more than unscientific and disingenuous for federal officials to emphasize 10 (as yet unproven) vaccine caused deaths among 130 million vaccine administrations. Even if there were 10 deaths, in the real world of inherent risks in all medical endeavors, this would be a highly regarded proof of excellent safety.
(4) Current policy makers have purposely chosen to avoid looking at immunization as inherently a population-based strategy striving for herd immunity. Sadly this has led to the lack of leadership in the appropriate and proven best response to the still expanding measles epidemic.
(5) It is human nature and unavoidable that during "shared decision making" any (or all) concerned moms would naturally discount the inherent increased value and benefit to the general community of vaccinating her child (even to accept the safe pain from the injection itself). This factor has been overcome in the past by public health policy educating the public on the community value of herd immunity. Current federal officials have deviously destroyed this dynamic.
RFK needs to be impeached for making decisions and policy without scientific data. The head of HHS needs to be qualified in the fields that he/ she runs.