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Delta Variant 

The Delta variant is more contagious: The Delta variant is highly contagious, much more so than previous variants. Preprint data estimates are 43% to 115% more transmissible. The CDC lists it as 2x more contagious.

Some data indicate that the Delta variant might cause more severe illness than previous strains in unvaccinated persons: In one peer reviewed study, patients infected with the Delta variant were approximately 1.85x more likely to be hospitalized than patients infected with other SARS-CoV-2 strains. However, other studies (not fully peer reviewed yet) have not found this effect.

Breakthrough infections (for those vaccinated with FDA EUA vaccines) are VERY rare, despite how the media portrays them. For example, the effectiveness of two doses of the Pfizer vaccine was 93.7% (95% CI, 91.6 to 95.3) among persons with the Alpha variant and 88.0% (95% CI, 85.3 to 90.1) among those with the Delta variant against symptomatic illness, as determined by a study that analyzed all COVID-19 tests over a 6 month period for all of England. (England has a central national health registry.) In Kentucky, while half of the population is fully vaccinated, vaccinated patients comprise only 1.1% of all hospitalizations for COVID-19.

Fully vaccinated people with Delta variant breakthrough infections can spread the virus to others. However, vaccinated people appear to be infectious for a shorter period: Previous variants typically produced less virus in the nasal cavities of infected fully vaccinated people (breakthrough infections) than in unvaccinated people. In contrast, the Delta variant seems to produce similar large amounts of virus in both unvaccinated and fully vaccinated people. However, just as with the other variants, the amount of virus produced by Delta breakthrough infections in fully vaccinated people decreases faster than infections in unvaccinated people. This means fully vaccinated people are likely infectious for less time than unvaccinated people, though data that quantify how much less time are not yet available.

Unvaccinated people remain the greatest concern: Although breakthrough infections happen much less often than infections in unvaccinated people, individuals infected with the Delta variant, including fully vaccinated people with symptomatic breakthrough infections, can transmit it to others. We do not definitively know whether fully vaccinated people with asymptomatic breakthrough infections are contagious. However, the greatest risk of transmission is among unvaccinated people who are much more likely to contract, and therefore transmit, the virus. Over 98% of all COVID-19 related deaths in Kentucky are in unvaccinated patients.

Masking protectivity is unchanged: The Delta variant is more contagious because it can bind more effectively to our cells and because our immune system is less effective against it. But its method of transmission from person to person remains the same.  While contagious individuals may shed more virus per unit time, if a person’s breath is appropriately filtered by a mask, then aerosol spread of SARS-COV-2 is stopped (or significantly mitigated, depending on mask type). However, it is important to remember that chin straps, mouth muffs, and ear dangles do absolutely nothing to prevent the spread of COVID-19.




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