Thanks!  And about the data we use for our decision-making…

Benicia Mayor and Council Members:

Thank you for continuing the mask mandate at your meeting last night. I really appreciate the time and attention you have been devoting to this issue. And I’m sorry to keep writing you, because I know you are all very busy. But I hope you can take a few minutes to read this email.

I am writing to express my concern with using only one metric — and a problematic metric at that — as the basis to decide to lift the mask mandate. And I also feel that the mask mandate should not be automatically lifted without further discussion at a meeting of the city council, even if one or more metrics are met.

Problems with case rate metric. There are two problems limiting the use of the case rate as a metric for measuring community transmission of covid-19. As Councilmember Largaespada has pointed out, the case rate depends on how many people are being tested. The second flaw is that increasing numbers of people are doing at home covid tests, and data from these tests does not get captured in the official case rate numbers. The use of at-home testing will continue increasing in the weeks and months ahead for obvious reasons. The case rate should be looked at, but is not in and of itself an adequate measure of covid in our city.

Other metrics can help. Eight of the nine Bay Area counties are using 3 metrics, as has been discussed previously. City data is available on two of the three, and county data is available for hospitalization rates. Using 3 metrics in combination would provide more clarity about the extent of the virus’ presence in Benicia. If only one metric is going to be used, either the vaccination rate or the (county) hospitalization rate would be less subject to sampling bias than the case rate. But since all three data points are available, why not use them? Each metric has some validity issues, so using all 3 together provides a more accurate picture.

Vaccination rate. There was some discussion at your meeting last night over how to view the vaccination rate. The specific issues were whether to use a numerator of people who have gotten at least one shot or those who are fully-vaccinated, should the denominator be the entire population or those eligible for vaccines, and differing vaccination rates by age.

(a) The fully-vaccinated rate is most meaningful. Data shows that a single shot (Pfizer) reduces risk of infection by 52%, while the second shot reduces risk by 95%. Similar date is available for Moderna. But immunity wanes over time. At 6 months after the second vaccine dose, people’s immunity is roughly the same as if they had only gotten one shot. Far fewer than half of fully-vaccinated people have received boosters yet, so the fully-vaccinated percentage overstates the proportion of the population who are well-protected. As far as what denominator to use, while I feel the best denominator is the entire population, it is reasonable to use a denominator of those eligible for vaccination, i.e. five years of age and up. According to California’s Department of Health and Human Services, 73.3% of Benicia’s population over age 4 is fully vaccinated as of November 30. (My statement last night that 67.7% were fully vaccinated was based on numbers from early November and using the entire population as the denominator). While 73.3% is a good number, we are still lower than the fully-vaccinated rate of most Bay Area counties.

(b) Vaccination rates by age. While older people are more vaccinated than younger, it is still important to try to safeguard younger people from this virus. Though the risk of death for younger people is lower, there is growing data on the prevalence of long-lasting symptoms among young people after covid infection. So, even though most of our city’s elderly are fully-vaccinated, we should not relinquish our efforts to protect all age groups. The virus is having a serious impact beyond hospitalizations and deaths.

Hospitalization rate. This metric is less subject to the vagaries of the officially measured case-rate data, but is not specifically available for our city. Another factor with this metric is that as treatment options improve, hospitalization rates will likely decline even if actual cases were to be increasing. Nonetheless, this metric can be helpful in combination with the other two metrics. As was noted at your meeting last night, hospitalizations for south county residents may well be lower than for north county residents. Nonetheless, the county’s hospitalization rate is a proxy for Benicia’s hospitalization rate, even if the actual number for Benicia is lower than the county’s. Solano’s current hospitalization rate is 10/100K. This is much higher than any other Bay Area county, and is also higher than the state’s hospitalization rate (9/100K). Even if Benicia’s residents are being hospitalized at a lower rate than the county, it is still most likely a higher number than in many other Bay Area communities.

Looking to the future. As was clearly articulated by several speakers at last night’s meeting, we need to not only look at the past, but try to anticipate the future. Looking at our hospitalization and local case rates trending down and vaccination rates trending up is indeed reassuring. As several of you said at last night’s meeting, the susceptible population in Benicia is shrinking. This bodes well for the future. But please take note of and keep in mind the following — even though all other Bay Area counties are much better vaccinated than we are, the case rates are trending up significantly in 7 of those 8 counties. Hospitalizations are also trending up in 5 of those 8 counties. Vaccination status is protective, yes, but recent trend lines in those counties point to a problem, likely due to cooler weather, holiday activities, and some degree of waning immunity.

Based on the above, I strongly urge you to do two things:

1. Switch to using 3 metrics to make decisions about public health safety measures to confront covid-19. Three metrics will provide a more accurate picture of the pandemic’s status in Benicia.

2. Do not lift public health measures based on auto-pilot, certainly not using one metric, but even if you decide to use 3 metrics. Instead, when the metrics are met, I urge you to then discuss the issue at your next city council meeting. There are so many other factors which may be at play even if the metrics are met, and a decision which can have such an impact on so many people’s health and welfare should be carefully thought through and discussed.

Thank you,

Richard Fleming, MD
Benicia, CA