DELTA Variant COVID: Delta Variant COVID, aka B.1.617.2, has been spreading across the globe. It will soon be the dominant form in the US.
Is it more contagious?
Will the vaccines work against it?
Is it a deadlier disease with worse symptoms?
In a study done in Scotland, which was published in The Lancet, researchers showed that the risk of being hospitalized with the COVID Delta variant is double that of the alpha variant. The covid delta variant has recently made its way to the US, constituting 10% of COVID cases. However, that figure is doubling every two weeks, and it’s only a matter of time before it becomes the dominant strain. It makes up about 25% of Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming in the Midwest.
DELTA Variant COVID
In a study done in the UK from May 20 to Jun 7th, the researchers, led by Steven Riley, looked at their data, which suggest that the covid delta variant is about 60% more transmissible than the alpha, which was the variant first identified in the UK, which was more contagious than the original strain that originally emerged from Wuhan. Furthermore, they showed a doubling time of 11 days with the delta variant and an estimated R (reproductive) number of 1.44. And those younger than age 50 were 2.5 times more likely to be infected than older people.
The data showed that the covid Delta variant’s affinity for the ACE2 receptor was slightly better than the original Wuhan strain. One of the delta’s mutations in its RBD is what allows for this. The virus uses its spike protein to bind to the ACE2 receptor in the body. It’s the key in the lock analogy. The virus then fuses with the cell membrane. This process relies on cleavage. Meaning enzymes on the cell membrane cut the spike protein at two different sites, triggering the cell to engulf the virus. A second delta mutation is in one of these cleavage sites. Better cleavage, better reproduction.
Another takeaway from this study is that the authors concluded that the neutralization of both viruses is reduced compared with the original Wuhan strains. Still, there is no evidence of widespread antibody escape. However, they said the data did suggest that those previously infected with COVID may be more susceptible to reinfection by the new delta variant. Also, it looks like monoclonal antibody treatments are ineffective at treating the delta variant.
The big concern is “vaccine escape,” meaning that the current vaccines will become far less effective as the virus evolved. So far, it hasn’t happened, but eventually, we will need new covid vaccines for the variants, likely a yearly thing. The good news? Covid Vaccines are still protective against the Delta variant.
According to research released by Public Health England: For the Pfizer vaccine, after both doses, it was 88% effective in preventing symptomatic disease, 96% effective at preventing hospitalization. The Oxford/AstraZeneca vaccine was 92% effective at preventing hospitalization if they had both shots. If you only get one shot of either of these covid vaccines, the effectiveness is pretty low, around 30-40%. More studies will soon be available when it comes to the Moderna and Johnson & Johnson vaccines.
Doctor Mike Hansen, MD
Internal Medicine | Pulmonary Disease | Critical Care Medicine