Get answers to some frequently asked questions about the Delta variant

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The Delta variant (B.1.617.2) has become the dominant form of SARS-CoV-2 spreading in the United States.

According to the Centers for Disease Control and Prevention (CDC), Delta made up more than 93% of new COVID-19 cases in the U.S. in the final two weeks of July.

With Delta spreading, it’s as important as ever to protect yourself against COVID-19. Below are answers to some frequently asked questions about the Delta variant and how to protect yourself.

Where Did the Delta Variant Come From?

Viruses change and mutate over time, causing variants. The Delta variant is just one of many variants of SARS-CoV-2.

The variant first emerged in India in late 2020 and quickly spread worldwide. It became the dominant variant in the U.S. in the summer of 2021. The CDC classifies Delta as a variant of concern, along with these other variants:

  • The Alpha variant (B.1.1.7).
  • The Beta variant (B.1.351).
  • The Gamma variant (P.1).

Graham Snyder, MD, medical director, Infection Prevention and Hospital Epidemiology, UPMC, says variants are common. The number of cases may vary because of factors like vaccination rates. And although Delta may fade over time, another variant could emerge.

“A future that I think is easy to predict, with most of the world unvaccinated by a long shot and with a lot of transmissions occurring, more variants are going to emerge,” Dr. Snyder says. “Delta won’t be the last.”

Is the Delta Variant More Contagious?

The Delta variant appears to be the most contagious variant yet.

A report by the Scientific Pandemic Influenza Group on Modelling, Operational (SPI-MO) sub-group said Delta was 40% to 60% more contagious than the Alpha variant. Delta is about twice as contagious as the original strain of SARS-CoV-2.

Along with Delta’s increased transmissibility, lowering of COVID-19 prevention tactics could be a factor in how quickly Delta is spreading.

“How much of this emergence is Delta being more contagious, and how much is human behavior giving it more opportunities?” Dr. Snyder says. “The answer is both.”

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Does the Delta Variant Make You Sicker?

Some data suggests the Delta variant may cause more severe cases of COVID-19. However, scientists are still studying it.

“The verdict is still out on how much more likely it is to make people sick, including requiring hospitalization or death,” Dr. Snyder says.

Do Vaccines Work Against the Delta Variant?

Yes, vaccines still work. The vaccines are safe and effective against SARS-CoV-2 and its variants. They are especially effective in preventing severe illness, hospitalization, and death.

The best way to prevent COVID-19 infection is by getting vaccinated.

Can I Still Get COVID-19 After Getting Vaccinated?


No vaccine is 100% effective, meaning breakthrough infections are possible. Fully vaccinated people can still get COVID-19 and spread it to others.

Breakthrough infections are rare. The vaccines are still very effective against COVID-19, especially in preventing severe illness, hospitalization, and death.

“The vaccine is really safe. It’s highly effective,” Dr. Snyder says. “But that doesn’t mean it’s perfect protection. We’re going to see people get sick.”

Some people may not have a robust immune response to the vaccine. That includes people with immune systems compromised by medical conditions or organ transplants. However, anyone can get sick with COVID-19.

Some data suggests that people infected with the Delta variant may carry high viral loads, even if they’ve been vaccinated. That makes them highly contagious. But the vaccine may make you contagious for a shorter amount of time.

Dr. Snyder says if you start to feel symptoms of COVID-19, you should get tested as soon as possible. Also, treatments like monoclonal antibodies can help if you do get COVID-19.

Why Should I Get Vaccinated if I Can Still Get COVID-19?

Because the COVID-19 vaccine is still the best way to prevent COVID-19.

Although breakthrough infections are possible, they are rare. The vaccines are especially important in preventing severe illness, hospitalization, and death. Unvaccinated people account for the high majority of COVID-19 infections, severe cases, and deaths. If you are not fully vaccinated, you are more vulnerable to COVID-19.

“The vaccine doesn’t make you invincible, but the vaccine is effective and safe,” Dr. Snyder says. “It does really reduce your chances of becoming sick, and particularly it does well at preventing you from being hospitalized or potentially dying of COVID-19. That’s an important risk difference, even if you’re young and healthy.”

By getting vaccinated, you also can protect vulnerable people around you. That includes people with compromised immune systems and people who are not eligible yet for the vaccine.

Do I Need to Wear a Mask After I’m Fully Vaccinated?

In July 2021, the CDC updated its guidance for fully vaccinated people.

The CDC recommends people wear masks indoors in public in regions with high levels of COVID-19 transmission, even if they are fully vaccinated.

The CDC also recommends teachers, students, and visitors in K-12 schools wear facemasks, even if they’ve been fully vaccinated.  On Aug. 31, 2021, the Pennsylvania Department of Health mandated K-12 students, teachers, and staff wear masks inside schools beginning Sept. 7. 

You should wear a mask if required by law, rules, regulations, or local guidance, even once you’re fully vaccinated. Everyone who comes to a UPMC facility must wear a mask.

People who are not fully vaccinated should wear a mask in public indoors and in crowded outdoor areas. People who are immunocompromised, or who live with or care for someone who is, may want to consider wearing a mask in some situations.

The COVID-19 vaccine reduces the risk of serious complications of COVID-19 if you are exposed to the virus. And while the vaccine helps reduce the risk of person-to-person transmission, that’s not what it does best. Masking and physical distancing provide an important layer of protection from being exposed to the virus. Wearing a mask can lower the risk of COVID-19 spread significantly.

“Masking and distancing is a good layer of protection, just like the vaccine is a good layer of protection,” Dr. Snyder says. “Neither of them are perfect, but together, they’re really, really, really effective.”

Is It Safe to Travel With the Delta Variant Spreading?

Many people are taking part in activities that they didn’t do for the first year or so of the pandemic. That may include travel, gathering with family and friends, going to the movies, or attending sports games or concerts.

Dr. Snyder says you should consider the risk to you and your loved ones. There may be ways you can make your experience safer. Getting the vaccine is one important step, and masking and physical distancing is another.

Before taking part in an activity, consider factors like:

  • Air circulation. Outdoor activities are generally safer.
  • Who’s attending. Is everyone fully vaccinated?
  • How many people are attending. Generally speaking, more crowded activities are riskier.
  • How close people are. Is it possible to physically distance?
  • What the activity is. Are you expending a lot of air?

For activities that are riskier, taking extra precautions like masking and physical distancing can help lower your risk.

When Will the Vaccines Be Approved?

On Aug. 23, 2021, the Food and Drug Administration (FDA) approved the Pfizer-BioNTech COVID-19 vaccine for Americans 16 and older. The vaccine had previously been distributed under emergency use authorization (EUA). The Pfizer vaccine also is available to children aged 5-15 under EUA.

On Jan. 31, 2022, the FDA granted full approval to a COVID-19 vaccine developed by Moderna for Americans 18 and older. The vaccine had previously been available under EUA.

A third COVID-19 vaccine, developed by Johnson & Johnson/Janssen (J&J), also is being distributed under EUA.

An EUA is not the same as a full approval. But to receive an EUA, the vaccines must meet FDA standards for safety and effectiveness. The COVID-19 vaccines have exceeded those standards, Dr. Snyder says.

“We’re confident in the vaccines, even if we’re just now giving them under emergency use authorization, because we have so much experience and scrutiny of them,” Dr. Snyder says. “I think approval is just a matter of time. I think it’ll be affirmation that we’re all confident these are safe and effective.”

Will We Need a COVID-19 Booster Shot?

Many Americans are now eligible for an additional dose or a booster dose of the COVID-19 vaccine.

Immunocompromised people who received one of the mRNA vaccines — Moderna or Pfizer — are eligible for an additional dose of those vaccines. Pfizer recipients must be 5 and older, while Moderna recipients must be 18 and older.

Scheduling an additional dose? Don’t forget to bring your COVID-19 vaccine card with you to your appointment.

People with compromised immune systems, such as from a solid organ transplant or other medical condition or treatment, may not have a strong response to the initial two doses of the vaccine.

Additionally, the CDC and FDA have authorized booster doses for other COVID-19 vaccine recipients:

  • Pfizer vaccine recipients who are 12 and older are eligible for a booster five months after their second dose.
  • Moderna vaccine recipients who are 18 and older are eligible for a booster six months after their second dose.
  • Johnson & Johnson vaccine recipients who are 18 and older are eligible for a booster two months after their first dose.

Additional and booster doses provide extra protection against COVID-19 and its variants like Delta.

For more information on additional dose eligibility, or to schedule an appointment, visit our COVID-19 vaccines page.

Editor's Note: This article was originally published on , and was last reviewed on .

American Society for Microbiology, How Dangerous Is the Delta Variant (B.1.617.2)? Link

Centers for Disease Control and Prevention, Delta Variant: What We Know About the Science. Link

Centers for Disease Control and Prevention, Understanding Variants. Link

Centers for Disease Control and Prevention, Variant Proportions. Link

Centers for Disease Control and Prevention, What You Need to Know About Variants. Link

Centers for Disease Control and Prevention, When You've Been Fully Vaccinated. Link

Scientific Pandemic Influenza Group on Modelling, Operational, SPI-M-O: Consensus Statement on COVID-19. Link

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