The United States is experiencing a spike in COVID-19 cases, specifically in areas with low vaccination rates. A major reason for this spike is an emerging variant known as Delta, which was first seen in India in December 2020. The variant has quickly moved across the globe, and it is now circulating in the United States as the dominant variant, accounting for 83.2% of COVID-19 cases, according to recent data from the Centers for Disease Control and Prevention (CDC).

This article discusses what Delta is, how it differs from the original COVID-19 variant and what it means for vaccinations.

What Is the Delta Variant?

As an increasingly dominant variant of the coronavirus, Delta has spread to at least 100 countries. Here’s what health experts have discovered about Delta:

  • Delta is about 40% to 60% more contagious and transmissible than the other virus variants, according to U.K. pandemic experts.
  • Unvaccinated people are at risk. Based on a U.K. study, unvaccinated children and adults under 50 years were 2.5 times more likely to become infected with Delta than other variants.
  • Delta could lead to hyperlocal outbreaks in areas with low vaccination rates that are surrounded by highly vaccinated areas.

There is still much to learn about Delta, so experts continue to study the variant in real-world conditions —specifically in the United States.

How Is This Variant Different?

So far, experts have shared the following general ways that Delta affects people differently than the original COVID-19 variant:

  • Delta is more transmissible than other variants.
  • A Delta infection can result in higher hospitalization rates for unvaccinated people.
  • Cough and loss of smell are less common symptoms of Delta.

Because of these significant differences, health experts agree that the Delta variant is concerning and will further impact the COVID-19 pandemic.

What Does This Mean for Vaccinations?

The good news is that COVID-19 vaccines authorized for use in the United States seem to work well against the Delta variant—drastically reducing the likelihood of severe illness, hospitalization and death for vaccinated individuals.

Additionally, research suggests that people who have recovered from COVID-19 still need to be vaccinated to fend off any coronavirus variants.

As new variants test the protections of the available vaccines, vaccine manufacturers are researching and developing booster shots. However, the CDC says fully-vaccinated Americans do not need a booster dose at this time.


The pandemic is an ongoing risk assessment, so health experts and the CDC will continue to monitor, research and update their recommendations to account for implications related to Delta. Vaccination offers the best protection against all coronavirus variants.