A scanning electron microscope image of SARS-CoV-2 (in magenta) emerging from the surface of human cells grown in a lab. Each infected cell can release up to 100 new viruses. Every time the virus multiplies in a cell, mutations are possible.

What you need to know

Variety is the spice of life except when it comes to viral infections like COVID-19, which is caused by the SARS-CoV-2 virus. The more that SARS-CoV-2 spreads, the greater the chance that its genetic material will change, or mutate, creating new variants or strains. The virus builds up mutations as it passes from person to person, possibly becoming a variant of concern (VOC). VOCs may spread more quickly, cause more severe disease, or be resistant to treatments and vaccines.

The good news is that every person has the power to help stop VOCs by slowing the spread of SARS-CoV-2.

Variants taking over

VOCs pop up in one spot, spread rapidly, and eventually dominate in some areas. For example, VOC B.1.1.7 — otherwise known as the Alpha variant — first emerged in the United Kingdom in September 2020. As of June 2021, it has been found in 144 countries and is the most common variant circulating in the United States.

John Mascola, M.D., director of NIH’s Dale and Betty Bumpers Vaccine Research Center, has been keeping an eye on SARS-CoV-2 variants.

“We know that the virus mutates more rapidly than we expected. As the pandemic continues, there will be more variants,” Mascola said. “Vaccines are less effective against some viral variants, and some treatments may not work as well either.”

Examples of SARS-CoV-2 Variants of Concern

Variant name

Where it was first found


B.1.1.7 (Alpha)

United Kingdom

  • Spreads more easily than original SARS-CoV-2 strain
  • May cause more severe disease
  • Monoclonal antibody treatments are effective
  • Vaccines are effective

B.1.351 (Beta)

South Africa

  • Spreads more easily
  • Some monoclonal antibody treatments do not work as well
  • Vaccines are less effective

B.1.617.2 (Delta)


  • Spreads more easily
  • Some monoclonal antibody treatments may not work as well
  • Vaccines may be less effective

P.1 (Gamma)

Brazil and Japan

  • Some monoclonal antibody treatments do not work as well
  • Vaccines are less effective














Source: Centers for Disease Control and Prevention (CDC). Retrieved July 12, 2021, from https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-info.html

Stop VOCs to stop the pandemic

It is important to get vaccinated and maintain COVID-19 safeguards, whether you have already been vaccinated or haven’t been vaccinated yet. Limiting the spread of SARS-CoV-2 gives it fewer chances to mutate.

Mascola noted that current vaccines still provide protection against VOCs and are especially effective at preventing serious disease and hospitalization.

“We need to get people vaccinated as fast as we can,” Mascola said. “We need to keep immunity at high levels, possibly by giving booster shots in the future. Most important, we need a global approach to fighting SARS-CoV-2 as it spreads and mutates.”

Where can I go to learn more?

COVID Data Tracker: Variant Proportions

The CDC is monitoring new and emerging SARS-CoV-2 variants to understand the implications for COVID-19 diagnostics, treatments, and vaccines.

Find a COVID-19 Vaccine Near You

Answers to common questions about COVID-19 vaccines and guidance on scheduling vaccine appointments.

How COVID-19 Spreads

Information on SARS-CoV-2 transmission and guidance on how to protect yourself against getting COVID-19.

New Variants of Coronavirus: What You Should Know

Experts from Johns Hopkins Medicine answer common questions about COVID-19 variants and their effects.


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News and Stories

Read stories about the efforts underway to prevent, detect, and treat COVID-19 and its effects on our health.

NIH COVID-19 Resources by Topic

COVID-19 research information and resources by topic from NIH institutes and centers