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Lambda, Gamma, Delta: What to Know About the COVID Variants Making Headlines

Current headlines featuring words like “delta,” “gamma,” and “lambda” might conjure images of sororities and fraternities, but they are instead reports on the COVID variants that have been appearing worldwide. Viral variants are a natural part of viral evolution, and the proliferation of variants alone should not be cause for alarm. Dr. Inci Yildirim, MD, PhD, a Yale Medicine pediatric infectious diseases specialist and a vaccinologist, confirmed this natural course of events in a Yale Medicine online article updated July 22 by acknowledging, “All viruses evolve over time and undergo changes as they spread and replicate.” Although many variants or viral changes can be inconsequential, some changes can elicit cause for concern if those changes make a disease more potent. Thus, while there are actually many variants of COVID, 5 key variants have earned spots on experts’ watch lists: Alpha, Beta, Delta, Gamma, and Lambda (with Alpha, Beta, Delta, and Gamma being the variants most notable in the U.S.). Much is still unknown about some of these variants, but the following information may be useful in understanding the variants currently making headlines.

What are the most common COVID variants, and when were they first detected?

The most common COVID variants currently in the news are Alpha, Beta, Delta, Gamma, and Lambda. The below graphic pulls from data shared by the CDC and NPR to track initial detection, by variant, both globally and in the U.S.:

First detection of COVID variants Alpha, Beta, Delta, Gamma, and Lambda (by location and month)

What is the dominant COVID variant in the U.S. today?

As reported by multiple news outlets including the Wall Street Journal, the CDC has confirmed that the Delta variant is now the most common COVID strain here in the U.S., accounting for 83% of analyzed infections as of July 2021. However, it is worth noting that there have been “hyperlocal” outbreaks of other variants within the U.S. Per The Hill, the state of Illinois “is reporting six times as many gamma variant cases of the coronavirus than delta variant ones.” By contrast, NPR reports that less than 1% of U.S. cases in the past 4 weeks have been identified as Lambda variant, with the first case having been reported at a Houston, Texas, hospital this past week. Commenting on the Lambda cases reported in Texas, Dr. S. Wesley Long, medical director of diagnostic biology at Houston Methodist, said that while aspects of the Lambda variant may be cause for concern, the Delta variant remains a greater threat. In an article from USA Today, he cautioned, “I know there’s great interest in lambda, but I think people really need to be focused on delta.”

What is different about the COVID Delta variant?

The most notable attribute of the COVID Delta variant is how highly contagious it is, with experts saying that this variant spreads 50+% faster than earlier strains. Speaking to CNN, Ashish Jha, dean of the Brown University School of Public Health, commented, “This is the most contagious version of the virus we have seen throughout the whole pandemic.” What makes the Delta variant so much more contagious and capable of rapid spread?

A group of Chinese researchers from the Guangdong Provincial Center for Disease Control and Prevention recently published a study examining the Delta variant. In their article entitled “Viral infection and transmission in a large well-traced outbreak caused by the Delta SARS-CoV-2 variant,” the co-authors shared their findings of a “higher viral replication rate” for the Delta variant, resulting in viral loads “~1000 times higher” than other COVID strains. They also noted that this increased infectiousness of the Delta variant can occur in early, pre-symptomatic stages of infection, contributing further to the variant’s high transmissibility. 

In addition to this increased degree of contagion, the Delta variant has also exhibited some differences in symptoms. According to Dr. Yildirim of Yale Medicine, “It seems like cough and loss of smell are less common [with the Delta variant]. And headache, sore throat, runny nose, and fever are present based on the most recent surveys in the U.K., where more than 90% of the cases are due to the Delta strain.”

Are the existing COVID vaccines effective against the Delta and other COVID variants?

The short answer is yes, they should be – thanks to how the existing COVID vaccines were designed. A recent Wall Street Journal article explained that COVID vaccines target the spike protein – a “distinguishing feature of the pathogen” that sticks out from the surface of the virus. Although the spike protein can change as the virus spawns new variants, the vaccines target a large enough portion of the protein such that none of the variants identified this far (including Delta) can elude the immune defenses that the vaccines trigger. These defenses cause vaccine-generated antibodies to bind to the spike protein and neutralize the virus.

The efficacy of existing COVID vaccines in fighting COVID variants (including Delta) comes with two caveats. The first caveat centers on vaccine dosage. In the same Wall Street Journal article mentioned above, researchers emphasized that two doses are needed to ensure a higher level of antibodies to offset the mutations inherent in COVID variants and trigger a stronger immune response. Dr. Akiko Iwasaki, an immunologist at Yale University, explained, “The second dose is going above that threshold of protection, whereas the first dose alone is inducing a suboptimal level of antibody that is just not enough to protect you from infection.” 

The second caveat is that having received a COVID vaccine is not a guarantee you won’t catch COVID – Delta variant or otherwise. This type of COVID case is called a “breakthrough infection,” and can be attributed to the significant variety in how human immune systems respond to pathogenic threats even with vaccine-enabled antibodies. However, the possibility of a breakthrough infection should not be a cause for alarm among those who are vaccinated. As NPR recently reported, “Though it’s still possible to get infected, the vaccines dramatically reduce the risk of serious illness” thanks to the pre-infection presence of antibodies from the vaccine. When describing to the Wall Street Journal how a vaccine works against a COVID variant, Dr. Saad Omer of the Yale Institute for Global Health used the following analogy: “It’s like you are training a pilot on one kind of a plane and a slightly different model shows up for the actual flight.” To extend that metaphor within the context of a breakthrough infection, some pilots (vaccine antibodies) may need some time to adjust to the slightly different airplane model (COVID Delta variant) before successfully taking control of the plane, but thanks to the “pilot,” the journey to health should involve minimal “turbulence” and a lower viral load. In fact, Dr. Anthony Fauci, chief medical adviser to the White House, has said that a vaccinated person with a breakthrough infection would be unlikely to transmit the virus due to a lower viral load. Speaking in a recent press conference, Dr. Fauci assured reporters that “When you look at the level of virus to be lower, that would mean you could make a reasonable assumption that those individuals would be less likely to transmit the infection to someone else.”

What is the best protection against current and future COVID variants?

Experts unanimously agree that the best protection is to receive a COVID vaccine. Speaking to USA Today, Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security, said, “If you’re a fully vaccinated individual and you’re meeting with somebody who has COVID, you really don’t have much to fear from the virus. The vaccines are very robust.” He then observed, “What we’re seeing now in the United States, as the CDC director said, is a pandemic of the unvaccinated. That’s where the risk is.” Epidemiologist Jennifer Nuzzo from the Center for Health Security at Johns Hopkins University shared a similar sentiment in a recent interview. She succinctly observed, “The safest way to protect yourself is to get vaccinated.” She then added this plea: “Please, not only get yourself vaccinated, but talk to your loved ones, friends, and neighbors and encourage them. It helps everybody.”

While the risk to vaccinated individuals posed by the COVID Delta variant (and other COVID variants) remains low, widespread vaccination still eludes the U.S. population. According to data updated on July 20,2021, by, 57% of the U.S. population has received at least one COVID vaccine dose, and 48% of the population has been fully vaccinated. This percentage falls short of the goal set by President Biden that 70% of U.S. adults would be at least partially vaccinated by July 4, 2021. However, in the face of increasing COVID variants, the gaps to close on vaccination underscore the importance of taking this step in mitigating the risk of COVID for individuals.

What other risk mitigation measures are available to combat COVID variants?

Given the variability in willingness to receive vaccination and the decreased willingness to engage in recommended behaviors like mask wearing, strategies that do not rely on human compliance are also available. These strategies include disciplined disinfection of shared spaces. While many disinfection methods are available, disinfection via UV-C light has emerged as a method that reduces waste, labor, and cost without the use of chemicals. UV-C destroys or inactivates bacteria, molds, and viruses — including SARS-CoV-2, E. coli, and influenza — by disrupting the molecular bonds of these microorganisms’ DNA and RNA. UV-C is the gold standard for disinfection in hospitals, and there are over 100 years of established clinical trials proving its efficacy in destroying virtually all known pathogens on surfaces and in the air. To date, there are no known UV-resistant microorganisms (viruses and bacteria) on the planet. To learn more about this sustainable disinfection solution, visit and discover the science behind disinfection enabled by UV-C light.

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