25 July 2022 Blog Post: On The Return of Masking, Summer 2022 Edition
Headlines this weekend across print and television media in Los Angeles essentially had the same message – COVID cases in the County while plateauing are high enough to bring back a mask mandate. The current threshold on mask mandate return has been set to an average daily rate of COVID-19 related hospital admissions exceeding 10 per 100,000 population. Measurements last week were 10.5 and 11.4 per the County Health Department.
So how do we evaluate this news? LA County Health makes it exceedingly difficult to double check their numbers as they do not actually publish raw data on hospitalization. Further, there is the very reasonable critique regarding classification of hospitalizations – are those patients admitted for COVID primarily or was the virus isolated as part of standard hospital screening protocol as is tangential to their admission diagnosis?
Before delving into that, let’s try to piece together what is actually happening in the community. First, whatever we can look at is about 2 weeks behind as, inexplicably, LA County Health has only published case data until 7/12/2022.
Cases are clearly increasing and are now at a rate almost double of what was seen in the Summer of 2020 and five times what we saw in Summer 2021 (Figure 1). This upwards trend began in May and clear separation from prior years was achieved by mid May (this would have been the time for mask mandates, if the Health Department was seriously concerned). I find it helpful to plot year over year as it provides some context both numerically and historically. In Summer 2020 we were all in our homes and not permitted to go to the beach. During Summer 2021, Delta began its slow breakout.
Many will argue (with some rationale), that with widespread vaccination and treatment that case rates no longer matter. And, to some extent, that is true. But what vaccination and treatment allow is a rise of the threshold of protection at the community level against mortality. For those that are unvaccinated, undervaccinated, immunocompromised or lack access to health care, mortality remains a risk. This is demonstrated in the Figure below which shows the mortality rate in 2022 which achieved a near historic low at the end of April (0.03 daily deaths per 100,000) beginning a steady rise, crossing over 2021’s rates (note that at the end of 2021’s graph we are just beginning to see the higher mortality rate associated the Delta variant beginning to creep in). The daily mortality rate is now 0.07 deaths per 100,000 (Figure 2 below). We are nowhere near pre-vaccination mortality rates however.
So clearly, more cases do lead to more deaths. Prevalence rate – which is a function of the number of tests and positivity rate is an attempt by me to account for home testing – is also clearly rising although is still dwarfed by the Omicron surge of December/January (Figure 3 below).
Now to the crux of the issue here – given that more cases in the community is now leading to more deaths in the community, can we identify those individuals among whom this is occurring? Of course we can and the answer isn’t terribly surprising – those that are older and unvaccinated (Figure 4 below, taken directly from the LA County Health website).
To what extent will community wide masking modify this risk? Not as much as one might think. In December of 2021, Abaluck et al. published in Science their results on community masking in Bangladesh showing an 11.9% decrease in COVID-19 symptoms and a 9.5% reduction in symptomatic seropositivity (those with COVID-like symptoms who also had antibody evidence of infection).
At this point in time, we are looking at a community-wide prevalence of at least 8%, so a decrease to 7.2% makes little impact. Far more effective from an interventional aspect would have been employing this mandate when prevalence rates were lower. At this point in time, a mask mandate is too little, too late. To say nothing of adherence, enforcement and pandemic fatigue amongst all of us.
Instead of a community-wide effort, I would advocate for situational masking (with an N95 or KN95) particularly among those who are unvaccinated or did not garner an immune response to a vaccination series (although Evushield, a long acting monoclonal antibody is a reasonable choice here and among those patients of mine who received such and subsequently contracted COVID-19, their symptoms were very mild). We continue to wear masks in our medical office with the assumption that patients coming in are, by definition, at higher risk than those in the general population. We also have an adult practice with a higher proportion of patients over the age 65 than most general practices. For this reason, you will see us with masks on in the office at all times.
In the future, Dr. Ferrar and the County Health Department need to be more aware of community case rates. Relying on hospitalization rates to determine policy is inherently flawed, as hospitalizations are a lagging marker and may be confounded by access to care and mis-assignment (hospitalized due to COVID versus hospitalized with COVID). This current increase in cases began in May and to have a discussion in late July about how to intervene is significantly flawed.
𝗦𝗶𝗴𝗻 𝗨𝗽 𝗳𝗼𝗿 𝗢𝘂𝗿 𝗡𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿
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