11 May 2021 Blog Post: On Containment and “Go For Zero”
If you missed it yesterday, a Bengal Tiger was on the loose in a Houston neighborhood. I found it interesting that somebody would keep on in their backyard, but also sort of terrifying (link: https://www.nbcdfw.com/news/local/video-shows-tiger-in-front-yard-of-houston-neighborhood/2628266/)
So what does a loose Bengal tiger in a Houston neighborhood have to do with COVID-19? I’m glad you asked. And while it isn’t customary to respond to a question, I’ll ask one. What, if you were a neighborhood resident, would be the first thing you’d ask after hearing about the tiger?
Most would say – was it caught? Or, in epidemiologic terms, was it contained?
An even better question would be “do I have to worry about it again?”
These are the same questions we should be asking as a community, a county and a country. Not “when will we reach herd immunity?” but instead, “when will we reach containment?” and then, “when will we eliminate COVID-19 entirely?”
So how do we know when we reach containment and what does it mean in practical terms? Lucky for us, the Harvard Global Health Initiative has defined containment as fewer than 1 new daily case per 100,000. As Figure 1 shows below, we are slowly approaching that goal here in Los Angeles County. We are now at 2.5 new daily cases per 100,000 population
The last two months have brought very slow (but steady) declines in incident case rates but more rapid decrease in mortality rates (Figure 2). The more steep decline in mortality indicates that vaccines (which provide essentially 100% protection against hospitalization and death) are indeed working.
So now that we have defined containment, and find ourselves at a caseload that only needs to drop by 1.5 new daily cases per 100,000 population – what’s next?
To find that answer, we need to turn to a country that has been successful in not just containing the virus but eliminating it – Australia. How did they do it? Quite simply, they moved past “flattening the curve”and “slowing the spread” but instead insisted upon “zero community transmission.” And they accomplished it without one very powerful tool which we have here in the US – they did it without vaccines.
- “A strong test-trace-isolate system is crucial in getting case numbers under control and preventing further outbreaks.” This takes an army of contact tracers – a reasonable estimate is 30 per 100,000 population which would mean 3,000 full time tracers in Los Angeles County. Further, at least 90% of identified contacts would need to be traced and it is here that we fall far short with 47% traced in the last 7 days, and 44% cumulatively (link: http://publichealth.lacounty.gov/media/coronavirus/data/contact-tracing.htm)
- “Be explicit about the goal and what should be done to achieve it.” This is also a point at which our US and County public health messaging has become muddled. The focus on ‘herd immunity’ and masking/unmasking obscures our overall goal which is to eliminate community transmission.
- “Be clear about when restrictions will be phased out (and in).” Again, this is another core issue, in California particularly where our tier system is being phased out. Without a structure, we are left to guess what we may be able to do and when we may be able to do it.
Let’s be very clear here, we have made tremendous strides in Los Angeles County and are approaching containment. A redoubled public health commitment from our County Health Department, most particularly when it comes to contact tracing, will get us to zero. Have you seen the pictures of Australians at concerts? Walking in crowds without masks? We are almost there – and with the huge advantage of protective, effective vaccines.
It is not enough to get to zero; one also has to plan to stay zero.
And, best of all, plan ways to celebrate it.
𝗦𝗶𝗴𝗻 𝗨𝗽 𝗳𝗼𝗿 𝗢𝘂𝗿 𝗡𝗲𝘄𝘀𝗹𝗲𝘁𝘁𝗲𝗿
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