I was hopeful that with widespread availability of vaccinations that I would be able to move onto other blog topics than COVID-19. However, I have had an increasing number of questions regarding the Delta variant  (B.1.617.2 first identified in India). To add a confusing wrinkle, the Los Angeles County Health Department is now “recommending” or “strongly recommending” (or even “urging” which is in the linked article title) that residents wear masks indoors – even if vaccinated (link: https://www.latimes.com/california/story/2021-06-28/as-delta-variant-spreads-l-a-county-recommends-everyone-mask-indoors).

The crux of the issue – probably best summarized by Jennifer Gould of the Associated Press:

“The L.A. County recommendation — which is not a mandate — in the nation’s most populous county does not match what the state government and the Centers for Disease Control and Prevention say, which is that vaccinated people in certain public indoor settings do not need to be masked.”

So why would the County make this recommendation?  Their justification is that the delta variant is more transmissible.This is, in fact, TRUE. The delta variant has primarily been linked to  a resurgence of COVID-19 in Nepal, southeast Asia and elsewhere. According to Public Health England, delta seems to be around 60% more transmissible than the already highly infectious Alpha variant (remember B.1.1.7? That’s now alpha) identified in the United Kingdom in late 2020. 

Another justification is that the delta variant is “spreading rapidly” in Los Angeles. According to County Health officials, “in the week ending June 12, it comprised nearly half of all variants genetically sequenced.”

 A third justification could be that the delta variant may be associated with more severe disease when compared to the Alpha variant.  In fact, Preliminary evidence from England and Scotland suggests that people infected with Delta are about twice as likely to end up in hospital, compared with those infected with Alpha. The County does not use this, however, as a rationale for indoors masking for vaccinated individuals.

Here is what is left out, however.  An excellent study by Public Health England (link: https://www.gov.uk/government/news/vaccines-highly-effective-against-b-1-617-2-variant-after-2-doses) has shown that 2 doses of the COVID-19 vaccines are highly effective against the Delta (B.1.617.2) variant.  Most germane to the United States,

“The Pfizer-BioNTech vaccine was 88% effective against symptomatic disease from the B.1.617.2 variant 2 weeks after the second dose, compared to 93% effectiveness against the B.1.1.7 variant”

Based on prior experience, we would reasonably expect that the Moderna 2 dose vaccination protocol would display similar efficacy to Pfizer-BioNTech and the Johnson & Johnson single dose vaccine somewhat less.

But let’s look at some actual data.  If the Delta variant comprised 50% of the cases in Los Angeles County by June 12th and is more transmissible, we should start to see an uptick in cases.  Figure 1 below shows the last 15 weeks of incident case rates in Los Angeles County (note: viral containment is defined as <1 new daily case per 100,000 population).