One of the latest terms to emerge from the pandemic is the Delta variant. This variant appears to be more contagious than previous variants and has become more common in the United States.
In this Q&A, Sean Liu, MD, PhD, an Assistant Professor of Medicine (Infectious Diseases) at the Icahn School of Medicine, says the spread of this variant is concerning because of the number of people who remain unvaccinated. Those who become infected with this variant pose an elevated risk to household members who are not vaccinated and to others they come in contact with, such as those with compromised immune systems—which includes those with chronic medical conditions and the elderly—who are not able to fight infections as easily as most. Dr. Liu is part of the team of experts at Mount Sinai who are at the forefront of research into vaccines and who are also on the front lines treating patients and helping to limit the spread of the virus in the New York metropolitan area.
Sean Liu, MD, PhD
What is the Delta variant?
All viruses, including the SARS-CoV-2 virus that causes COVID-19, will evolve over time. It is normal for a virus to change a little bit when it makes copies of itself, or replicates. These changes are called mutations. The virus with one or more new mutations is referred to as a variant. Genetic variants of SARS-CoV-2 have been emerging and circulating around the world throughout the COVID 19 pandemic. There are six variants of concern circulating in the United States; the Delta variant is one of these circulating variants. The Delta variant was first detected in December 2020, and recently this variant has been detected in more than 80 countries, and in all 50 states.
Why is there a concern over this variant?
The variants of concern show evidence of at least one of the following five properties:
- The variant may spread more easily from person to person.
- The variant may lead to more severe disease, including increased hospitalizations or deaths.
- The variant may be significantly harder to combat by antibodies generated during a previous infection or vaccination.
- Treatments or vaccines may show reduced effectiveness against the variant.
- The variant may evade diagnostic detection.
The Delta variant, specifically, has three of these properties, one being increased transmissibility. There is a 1.6-fold increase in the odds of household transmissions for the Delta variant compared with the Alpha variant, also known as the UK variant.
Why is the issue of transmissibility so important?
The fact that this strain can spread so quickly means is that you have a higher likelihood of spreading the Delta variant if infected. As clinicians, we see a lot of COVID-19 spread throughout families. It’s very devastating among households, and this variant specifically has this increased transmissibility within a household. People who are unvaccinated are really putting their family members, or those in their household, at increased risk for severe disease, especially if they too are unvaccinated.
For those who are fully vaccinated, does the Delta variant pose a risk?
It is important to remember that the goal of the COVID-19 vaccines is to prevent severe infections, hospitalizations, and deaths. The mRNA-based vaccines are about 95 percent effective against hospitalization for COVID-19, with either one or two doses. Studies suggest that the Pfizer-BioNTech vaccine reduced the odds of symptomatic disease from the Delta variant, which means getting mildly sick, by 36 percent after one dose and 88 percent after two doses. There is, however, no available data about asymptomatic or mild infections with the Delta variant in fully vaccinated people, which means that people can get infected but not show any symptoms. Also, we know that people with underlying medical conditions have died from COVID-19, even after being fully vaccinated. As a result, the Delta variant creates a major concern if there are fully vaccinated people who are in close contact with family or household members or with people who are immunocompromised or have not been vaccinated, including children.
What about those who are not vaccinated?
If you have not been vaccinated yet, you should seriously consider doing so now. People who have not been vaccinated have a much greater risk of getting seriously ill or dying from COVID-19, especially the Delta variant. Meanwhile, people who are not vaccinated, or who are immunocompromised, should continue to use masks, socially distance to avoid infection especially if you don’t know the status of the individuals around you. If you’re unsure of getting vaccinated, I would encourage you to have discussions with medical professionals who may provide reliable information about the benefits of vaccination. Currently, 44 percent of New York City residents of all ages have not been vaccinated and 34 percent of adults have not been vaccinated in New York City. The distribution of people getting vaccinated is not even. Check out the New York City Department of Health website for the latest information about vaccine availability and vaccination rates.
Why are vaccines important?
The COVID 19 pandemic is a global problem. While vaccines are becoming readily available in the United States, the majority of the world remains unvaccinated. And the pandemic will persist for months, and likely years. Vaccination is our primary means of ending the pandemic. Vaccines are safe and effective. Please consider getting vaccinated, if you are eligible.