December 3, 2022

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Bay Area health officer on how much to worry about BA.5


The BA.5 subvariant of omicron is fueling an increase in COVID-19 transmission across the San Francisco Bay Area, spawning headlines warning that the coming surge could be the “biggest yet.”

Marin County Health Officer Dr. Matt Willis agrees that BA.5, which is more contagious and has a greater likelihood of causing reinfections than past omicron subvariants, could cause record-high transmission. However, he’s much less concerned that the surge will result in a wave of hospitalizations that put stress on the health care system or a wave of long COVID cases that constitute“mass disabling event.”

In January, SFGATE spoke to Willis about why the omicron variant was the end of how we approached the pandemic in 2020 and much of 2021. At the time, Willis said that omicron was causing less severe disease, and that hospitalization numbers were misleading because many reported “hospitalizations” were for other causes. That trend is holding: Of the 19 reported hospitalizations in Marin County on July 14, only eight are “for COVID” hospitalizations; the other 11 are patients being treated for other conditions that happened to test positive for COVID-19 after admission.

SFGATE spoke with Willis again Monday to talk BA.5 and the future of policies such as mask mandates and quarantines. The interview has been lightly edited and condensed for clarity.


SFGATE: Let’s start with what we know about BA.5 itself. What’s different about it when compared to past omicron variants? When we last talked, you said original omicron was more of an upper respiratory disease than a lower respiratory disease, and that was leading to more mild symptoms. Is that holding?

Willis: Yes, that’s still holding. The most important difference between BA.5 and variants like BA.2 [an omicron subvariant] is BA.5 is more contagious, which comes in two parts. One, the likelihood that if we sit down together, I’ll infect you if I have the virus. Two is how fast it can move through the community, which is related to one but not the same. One of the reasons BA.5 moves through the community easily is because it’s able to evade the immune system more effectively, meaning it cares less if you’ve been vaccinated or previously infected. 

It can also move through the community easier because it keeps people infected for longer. If someone is infectious for, say, five days, you’ll have a certain number of additional infections. If someone is infected for twice as long, that’s twice as many additional infections. The length of how long people are infected for is an important determinant, and with BA.5, people are infected a little longer.

SFGATE: A little longer?

Willis: About two days longer.

SFGATE: Anything new with symptoms?

Willis: We’re not seeing big differences in Marin with symptoms from BA.5. The literature from abroad suggests it’s not more virulent than other strains of omicron, so we’re fortunate.

SFGATE: What’s there to know about BA.5’s reinfection powers? As someone who was infected in mid-May, presumably with BA.2, how much protection do I have against infection? How does that protection compare to people who got original omicron in the winter?

Willis: We don’t have a great answer yet because we’re still in the early days of the BA.5 experience here. We’re hearing from elsewhere that people can be reinfected more quickly. In Australia, they switched their definition for reinfection to anything after 28 days. We used to use 90 days as the interval, so any positive test within 90 days wasn’t considered a reinfection.

That interval gets shorter and shorter with new variants that are able to evade the immune system more easily. Right now it looks like it’s possible to be reinfected even within a month of past infection, but we will need a couple more weeks of data to see what’s happening. The evidence is clear that the reinfection risk is high enough to where people should get the protection of the second booster if eligible. Some people were holding off especially if they were infected more recently, and knowing there may be another omicron-specific vaccine in the fall. But now we see the reinfection risk of BA.5 is high, so that’s an argument to get the second booster if you’re eligible.

SFGATE: When we talked last about omicron, you said it’s important to contextualize its risk relative to other diseases like the flu. Your hospitalization numbers are still low and cases are being dramatically underreported because of at-home tests, so the case-to-hospitalization ratio is extremely low right now. Where is BA.5 when compared to past COVID variants, as well as the flu?

Willis: BA.5 is really fresh for us. We’ll have better answers in a couple weeks when we’re confident everything we’re seeing in hospitals is BA.5. Right now, it’s a mix of BA.2 and BA.5.

It is worth noting that we have never seen this long an interval of high transmission in the region. We’ve had three months of over 100 cases per day day. That’s the longest interval of high transmission since the start of the pandemic, and our hospitalizations are still low. We also know that our cases have never been more undercounted than they are now. We know that because wastewater figures are similar to the first omicron wave in the winter, but our measured case counts are one-third of what they were then.

Another sign of underreporting is 5% of people coming into the hospital for all causes are testing positive, which is a good sign of community prevalence. Around 1 in 20 people in Marin County have the virus right now.

We’re confident that the risk of being hospitalized due to COVID-19 is diminishing relative to earlier stages of pandemic. The virus is just not as damaging to us as a community as it has been despite us seeing more cases. And that’s because the virus itself has evolved to being less virulent, and also because our immunity as community is better than it was in previous waves. You would be hard pressed to find someone in Marin who doesn’t have some type of immunity — over 95% of us are vaccinated — so it’s hard to find someone who hasn’t been vaccinated, infected or both. We’re also better able to treat people who do get hospitalized. All three are factors changing the game of consequence of infection.

The one wild card is long COVID, which is still something we don’t know enough about. If we could just look at hospitals and say that determines our policies, I’m pretty sure we’re OK in not having things like mask mandates. However, if some fraction of people develop long COVID that’s going to add up, even if it’s a small fraction of cases. But the latest data on long COVID is reassuring. Your risk of getting it is connected to how sick you were originally. People who are hospitalized are the most likely to get it. People with mild symptoms getting long COVID is very rare.

Things that reduce disease severity like vaccination, age, and whether you get omicron as opposed to an earlier strain of the virus will reduce the risk of long COVID. Rates of long COVID are lower with omicron than they were with delta. All the latest evidence reassures us that going forward, long COVID won’t be as significant to the long-term impact of pandemic as we thought it might be.

SFGATE: If the consequences of infection have changed dramatically, are you sticking by the rule that if Marin has five hospitalizations per 100,000 residents a mask mandate comes back? Alameda brought back a mask mandate last month and its trends mirrored neighboring counties without mask mandates.

Willis: Los Angeles County is doing a mask mandate on July 29, but we are not planning on imposing a mask mandate here. The only scenario I see in which we’d bring back a mask mandate is if there’s a surge caused by a variant that is both more infectious and more virulent. A variant of that type would lead to more people coming into the hospital, which is the only reason for a mandate: relieving stress on the health care system. If BA.5 had the risk of creating a surge that’d overwhelm hospitals, we could consider a mandate, but as of now, I’m pretty confident BA.5 is not more virulent than past strains — though I don’t want to be overconfident. We’ll know more soon.

For the long term, this virus is going to be with us for years. Our long-term strategy needs to be for people to understand risk in the context of their own lives, and make decisions to protect themselves and those around them. Our approach is to provide that knowledge, so if one in 20 people are walking around positive, that means if you’re in a grocery store, there’s a 92% chance someone in there is infected.

A well-fit high quality mask like an N95 is very protective against being infected. We strongly recommend wearing masks indoors in Marin given the high rates of transmission, but we’re not going to institute policies that require people wear masks at this point. Our hope is that by understanding risk, people will able to take that agency and make the decisions best for them.

SFGATE: What do you see happening when schools reopen in August?

Willis: It will be a challenging fall for schools because there will be transmission. We will have cases of BA.5 still moving through the community in August because it’s just starting to crank up regionally now.

We won’t move to mandate in schools at the county level, but individual schools may adopt policies to encourage face coverings. School closures are really harmful to kids, so we should do whatever it takes to keep them in schools. What will be disruptive is kids staying out of class if they test positive. We need to make sure the curriculum is flexible to ensure they don’t fall behind. Those are the biggest concerns schools will be dealing with.

SFGATE: How much longer do you think people will need to quarantine as we have been over COVID?

Willis: I think that’s a great question and I don’t know the answer. A lot will depend of the severity of illness. If the virus continues to evolve to cause less severe illness, that will be important factor. SARS-CoV-2 is a coronavirus, which is in the family of common colds. We don’t take the same precautions and have an expectation of isolation for those with colds.

We could shift to where the social harm of isolation is worse than the harm of severe illness, but we’re not there yet. We’re at the mercy of the mutations of the virus as it moves across the globe. The likelihood is we’ll continue to move in the direction of more infectious, less virulent versions of the virus, and from there we’ll have important conversations about changing the guidance on isolation. But that wouldn’t be done at the local level, it’d be CDC. The length of isolation may change, as might the criteria for ending isolation.

SFGATE: How do your general worries for this wave regionally compare to the original omicron and delta waves?

Willis: The most damaging period of the pandemic is behind us. The early signs are that collective immunity levels are strong in the Bay Area thanks to very high vaccination rates and the more recent experience of infection and the natural immunity that results from that. There’s also the protection of the second booster, as well as a potentially new vaccine in the fall that may have some omicron in it. These are all factors I find reassuring that we won’t see the damage from those earlier waves, even if there are more cases.

SFGATE: So when compared to the winter omicron wave, there will be more virus out there but fewer hospitalizations?

Willis: I think that sounds right. BA.5 is more infectious, and I know more people in my social circle that have been infected in the last two weeks than at any other point in the pandemic. But none of them are ending up in the hospital and I expect that pattern will continue.



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