The Delta Variant and Boosters

COVID letter Aug 2021: The Delta Variant and Boosters

Hello again! I have put off writing this latest COVID update in part for 2 reasons: one, the strange sense of disbelief that there is still a need for these updates, and two, because a part of me hoped that vaccination rates would rise and things would start to get better. Unfortunately, that has not proven to be the case. Why is this Delta variant so significant? There are 3 parts to this. Among non-vaccinated (including children), it is looking like it is more virulent (harmful) in part because where the mutation is on the spike protein means it can destroy cell more easily. Second, nasal swab testing has shown us that the viral load that an infected person, including the vaccinated, can carry is approximately 1000x higher than the original strain. Finally, remember me talking about R0 (R naught) a year+ ago? This is, on average, the number of people an infected person will infect. The R0 of the Delta strain is somewhere in the 5-8 range, meaning that each person with the Delta variant will infect 5-8 more people. For comparison, the original COVID-19 strain had an R0 of 2.3-2.7. Influenza has an R0 of 2. The R0 of SARS in 2002 was 3. Chickenpox has an R0 of 10, and for measles, that number is 18.

How did we get a mutation like this? Simply put, our vaccination rates as a country (and obviously as a world) are not high enough. If a virus can replicate (ie infect people) it can mutate. The entire goal of a virus is to survive and it will naturally develop changes that allow it to survive the easiest.

Luckily, our vaccinations are doing their job. They have been very effective at preventing severe disease (ie hospitalization and deaths). Those that do get infected may only have mild symptoms (although they still carry high viral loads and are still contagious).

In general, why are vaccinated people now getting COVID at significantly higher rates than even 3 months ago? It appears to be a perfect storm of events:

1. Delta is so much easier to catch and to spread, as discussed above.

2. The spread of Delta has coincided with the relaxation of our social distancing and mask wearing.

3. And finally, the effectiveness of the vaccine does seem to be lessening the further away we get from the time the vaccine was given. A recent study showed that the Delta infection rate is higher in people who were vaccinated early, vs those vaccinated more recently. This is not a surprise. Almost all vaccinations require a booster for long-term effectiveness. In the US, the decision was made to give a second shot quickly to provide higher protection immediately. This likely prevented many deaths in the spring that would likely have occurred had we just had a single shot. However, the downside is that now our immunity is starting to wane, especially in those with compromised immune systems who may not have had as much of a robust response initially.

This leads me to my next topic: boosters. Last week, the FDA authorized an additional dose of an mRNA COVID-19 vaccine for those who are immunocompromised (see end for the list of qualifying immunocompromised criteria). This week, the US also announced that everyone who is vaccinated should receive a booster dose 8 months after they were given their second dose. The FDA is still conducting a review but it is likely that the boosters will start with those 65 and older, those in chronic care facilities, and health care workers.

So what next?

If you are vaccinated, you are fairly well protected from severe illness due to COVID-19. However, you are still at risk for mild to moderate symptoms. Especially if you are around those who are high risk, or have children who are not yet vaccinated, take precautions so you don’t spread the disease to them. What are these precautions? It’s the simple things we were doing a year ago: wear a mask, especially in crowded situations and indoors, follow social distancing guidelines, and wash your hands regularly. Although in general our vaccination rates in Colorado are fairly good, there are still 606 people hospitalized with COVID-19 in our state. I anticipate that this will get worse before it gets better.

We have ordered Pfizer vaccine and will let you know when/if it arrives. As always, we are available for questions and concerns about the Delta variant, boosters, and COVID-19 in general.

Stay healthy and safe,

Dr. Husney

CDC definition of immunocompromised who now qualify for an mRNA COVID-19 booster: those receiving active cancer treatment for tumors or cancers of the blood, organ transplant recipients who are taking immunosuppressants, those with a stem cell transplant in the last 2 years, those with a moderate or severe primary immunodeficiency, those with advanced or untreated HIV infection, and those currently being treated with high-dose steroids or other drugs that can suppress the immune response

For reference: https://www.nationalgeographic.com/science/article/why-is-delta-more-infectious-and-deadly-new-research-holds-answers