In focus: COVID-19 vaccines and the Delta variant

Dr. Purvi Parikh

Like medicine, the coronavirus disease (COVID-19) has shown to evolve over time, and it’s up to doctors like St. George’s University graduate Purvi Parikh, MD ’08, an allergist, immunologist, and vaccine researcher at New York University Langone Health, to guess where it’s going next.

Transmission of the Delta variant has contributed to a rising number of new coronavirus cases in recent weeks, including more than 100,000 cases each day in the United States this month according to the Centers of Disease Control and Prevention (CDC). Dr. Parikh explained what has made the Delta variant so difficult to contain, and how widespread vaccination would contribute to the health of everyone.

St. George’s University: We have seen a rise in the Delta variant in the US and worldwide. What makes it such a threat?

Dr. Purvi Parikh: The Delta variant is much more contagious than original strains of virus, even as contagious as chicken pox. Also, it is far more virulent—1,000 times more virus is found in people’s lungs with the Delta variant compared to previous forms of virus, and thus it can be more dangerous.

SGU: How does a virus mutate and why does the Delta variant present a different challenge than its predecessors?

Dr. Parikh: This is a normal part of viral life cycles. Viruses mutate when they pass from host to host and need to find new ways to survive as our immune systems become used to them. If a virus cannot replicate, it cannot mutate, thus it is much more likely to mutate in unvaccinated hosts rather than vaccinated. However, the challenge is that these mutations are making the virus more contagious and virulent and posing risks. Currently, our numbers of those in hospital and dying are quite high with Delta variant, and the majority of them are unvaccinated.

SGU: Are the symptoms different from earlier variants of COVID-19?

Dr. Parikh: Symptoms are similar; however, by sheer numbers of hospital and ICU admissions, it appears more severe. It is unfortunate because we are in worse shape in some areas of country compared to a year ago despite having the vaccine.

SGU: Do you expect there to be other variants in the future?

Dr. Parikh: If vaccination rates do not improve, yes. The Lambda variant, which is also very contagious and severe, is spreading through south America already.

SGU: How important is it for people to get vaccinated? How does the Delta variant affect the vaccinated versus the unvaccinated?

Dr. Parikh: Extremely important. If you are vaccinated, you have a significantly lower chance of hospitalization and death. Over 95 percent of those hospitalized are unvaccinated, and 99.5 percent of deaths are unvaccinated per the CDC.


“The Delta variant is much more contagious than original strains of virus, even as contagious as chicken pox. “

SGU: How are infectious disease and immunology specialists like yourself working to combat the Delta variant? 

Dr. Parikh: I am an immunologist and allergist—like Dr. Anthony Fauci—and I’m currently working on multiple COVID vaccine trials. I am involved with the initial trials with Pfizer, AstraZeneca, and Sanofi, which will be ongoing for next two years, and I’m also working on a booster study with Pfizer given the new variants. I also have a study with the NIH studying the vaccine in new moms and their babies (Momivax). These moms received the vaccine while pregnant. All of these studies are looking into Delta variant given it is the most common strain now.

SGU: What is the most exciting part about your job?

Dr. Parikh: I was attracted to the field for many reasons, but I saw immunology as the future for treatments in virtually every specialty. My father is an allergist and immunologist, and even between when he trained and I did, things have changed immensely. Our understanding of the immune system and its importance is so different.

I took care of a patient with a primary immune deficiency in residency, and I was so impressed at how important an immune system is not only in infections but in cancers and autoimmune conditions. I also realized how important immunology is in a pandemic as I helped with H1N1 vaccine trials when I was an internal medicine resident at the Cleveland Clinic. That was also the first time I came to know Dr. Fauci was an immunologist.

On the flip side of the field, allergies and asthma are also immune conditions on the rise, and being the doctor to effectively diagnose, manage and treat these disorders is so rewarding. Further, I enjoy building lifelong relationships with my patients and being able to treat both children and adults.

SGU: How did SGU set you up to be successful in your career?

Dr. Parikh: SGU gave me the opportunity to be a physician and embark on one of the most rewarding, humbling, and noble professions. Without being a physician, I would not be able to restore health and advocate for the health of others—both passions of mine. And as an investigator on the COVID vaccine trials, I would not have been able to step up when needed to help the world move one step closer to ending the worst pandemic we have seen in 100 years.

– Brett Mauser

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