Just when it felt like life was getting back to normal, masks have become an issue again. I have had quite a few of my patients asking why, so I thought I would share some of the data behind the shift in the CDCs recommendations.
Changes to the Spike.
Before Delta, COVID-19 variants gained an edge over our immune system by making changes to the viral core and viral binding sites. Delta is unique by making changes to the spike of the virus. Changes to the spike would be similar to cutting your hair or shaving your beard. It is still you, but most people would have to look twice to recognize you. The part of the virus that had been so stable and easily recognizable by our immune system is starting to disguise itself. Since all the vaccines have targeted the spike on the virus, our immune system has a more challenging time recognizing Delta. Look at the chart below from a recent study published in the Lancet Journal. On this chart, the lower the black dot in the pattern, the less protective our immune system is against the virus. Notice how the Delta (Light Blue pattern on the right of the chart) level is lower than the other variants.
Age does matter.
In the same study mentioned above, researchers measured how two doses of the Pfizer-BioN-Tech vaccine reacted in people age 40 and compared that response to people age 60. Like the last chart, the lower part of the chart represents a weaker response by the immune system.
Time does matter.
Finally, the study in Lancet measured antibody levels at 25 days after the second dose of the vaccine and compared them to the immune system at 100 days. It is clear that our immune system’s memory of the COVID virus is not as good we initially hoped. Note that with the Delta variant (B.1.617.2), a few of the results showed virtually no ability to Neutralize (kill) the virus at 100 days.
With changes to viral spike and the waning immune response with time, vaccinated people are at higher risk of catching the Delta variant, passing it along to others, and even feeling symptomatic. The good news is that in a recent publication by Public Health England, less than 5% of their hospitalized patients were fully vaccinated.
R naught (R 0) is a value used to describe the contagiousness of an infection. An R 0 of one means one infected person will infect one non-infected person. The R 0 of the original (wild-type) COVID-19 virus was 2.8. To put that into perspective, the Spanish Flu of 1918 had an R 0 of 1.8 and the annual flu we have today is usually less than one. The R 0 of the Delta variant is currently between 5-9.5 depending on the location and percent of that population that is fully vaccinated. This makes it one of the most contagious infections we have ever had in the world (only Measles, Mumps, and Chickenpox have a higher R 0).
When COVID-19 first spread around the world, medical providers did not know how to battle the virus. 33% of hospitalized people were dying. Over the past 18 months, medical providers have dramatically improved your odds of surviving COVID-19. Less than 5% of patients hospitalized are currently dying. Because of our advancing knowledge of treating infected COVID-19 patients, it is difficult to know if the Delta variant of the virus is truly more dangerous than the original virus. We do know that 1 out of 10 people who are not vaccinated are catching Delta. Compare that to 1 out of 1300 people who are fully vaccinated (breakthrough cases). Thank goodness for our advances in medical care, the effectiveness of the vaccine, and that the original virus was not as contagious as Delta.
With the changes to the COVID-19 spike, the waning levels of neutralizing antibodies, and the increased contagiousness of the Delta variant, masks once again become a great line of defense until we can get an effective booster. With only 43% of Texans fully vaccinated, you are more likely to encounter an unvaccinated person than a vaccinated one. As hard as it is, I am again wearing a mask when I go to the grocery store, trying to avoid high traffic areas, and trying to limit my social gatherings to people that I know are vaccinated. I hope the information above encourages you to do the same.
As always, please feel free to email me with any specific comments or questions.
Nelson X. Simmons, MD