Health Care Provider Resource Center

Last updated July 30, 2021

Since the COVID-19 pandemic began, several variants of the virus have emerged. But the one named delta is now the most severe of them all. This highly contagious variant was first identified in India in December 2020. Within six months, it spread to 85 countries. Now it's in all 50 of the United States, where it's become the dominant strain of COVID-19 .

Infectious disease expert David Tweardy, M.D., answers questions about this newest variant.

What is the delta coronavirus variant?

Originally known as B.1.617.2, the delta variant is the most infectious version of the COVID-19 virus to date. It was first identified in India in December 2020, where it quickly overwhelmed that country’s health care system.

How widespread is the delta variant in the U.S.?

It’s becoming more widespread every day. Infections nationwide tripled in July, from about 13,000 cases per day to more than 56,000. 

How contagious is this variant?

It’s extremely contagious, more than any other variant. Preliminary research suggests that the delta variant spreads from person to person more swiftly than the common cold or chickenpox.

SARS-CoV-2 is the original coronavirus that mushroomed out of Wuhan, China last year and led to the COVID-19 pandemic. Variants quickly emerged, including Alpha, which was first identified in the U.K. Alpha is estimated to be 50% more contagious than SARS-CoV-2. Delta is estimated to be 50% to 60% more contagious than Alpha.

What makes delta more contagious than other strains?

Delta infects people with a heavier virus load, which means they exhale more virus particles for others to catch. The delta variant’s mutations are also believed to make it more effective at attaching itself to cells in human airways.

Does it cause more severe illness than other variants?

Scientists are still investigating this, but a study published in The Lancet medical journal estimated that the risk of hospitalization after infection with delta could be 85% higher than with alpha.

In China, doctors are reporting that patients with the delta variant are sicker than those they treated early in the pandemic. And their condition seems to go downhill much faster. Recent Scottish studies suggest that people infected with the delta variant are almost twice as likely to be hospitalized as those infected with the alpha variant.

Does the Delta variant cause any unusual symptoms?

COVID-19 delta symptoms include headache, fever, sore throat – the same as those caused by other variants and the original SARS-CoV-2 virus. However, two typical COVID-19 symptoms are absent in delta patients – cough and loss of smell.

Who’s most at risk for the delta variant?

People who are unvaccinated.

In the United Kingdom, where delta is the dominant strain, studies showed that children and adults under age 50 are more than twice as likely to become infected. This is the age group with the lowest vaccination rate.

Will current COVID-19 vaccines work against the variant?

Yes, absolutely. We know that vaccines protect people against the delta variant. But a single dose doesn’t offer as much protection. It’s vitally important to follow up and get that second dose.

What about breakthrough infections?

It is possible that vaccinated people can still become infected with the delta variant, but those infections are infrequent. When they do occur, they're likely to be far less severe than infections in unvaccinted people. The vaccines have proven to be highly effective at preventing severe disease and death, but they are not 100% guaranteed to prevent you from getting the virus.

Can vaccinated people pass the delta variant to others?

New research suggests that vaccinated people who are infected with delta, even those who display no symptoms, may be able to transmit the virus as easily as those who are unvaccinated. Early studies show that infected vaccinated people have viral loads similar to infected unvaccinated people.

That's why the CDC has updated its mask-wearing guidelines and is now recommending that vaccinated people who live in high-transmission areas resume wearing maskes indoors.

Can we expect future delta mutations?

Viruses are built to mutate. With each mutation, a new and stronger variant can emerge. The best way to prevent this is to vaccinate as many people as possible. Variants are less likely to emerge when a pandemic is brought under control.

Do the COVID-19 vaccines protect immunocompromised cancer patients and survivors?

Yes, the COVID-19 vaccines are safe and recommended for cancer patients. Most people with cancer or a history of cancer are advised to get the COVID-19 vaccine. Some cancer treatments like chemotherapy, radiation, stem cell transplant, or immunotherapy can affect the immune system, which might make the vaccine less effective. People with cancers of the blood or lymph system can also have weakened immune systems which might lessen the vaccine’s effectiveness.

Despite this, we still recommend vaccination for cancer patients. Getting some protection from the vaccine is better than not having any protection. Every situation is different, so talk to your doctor about vaccine timing and the risks and benefits.

Young children can’t get vaccinated. What about them?

The FDA has not yet approved vaccines for children younger than 12 years. Children ages 12 and older are eligible for COVID-19 vaccines in the U.S. Parents should vaccinate their children as early as possible and, if they’re not eligible for vaccination yet, continue to take precautions, such as masking and social distancing. The Centers for Disease Control is now also recommending that all teachers, staff and students wear masks in schools, regardless of their vaccination status.

Request an appointment at MD Anderson online or by calling 1-877-632-6789.

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For many years, brachytherapy has been used to treat low-risk, intermediate-risk, and high-risk prostate cancer. But more recently, doctors have been using a more advanced form of brachytherapy called MRI-assisted radiosurgery (MARS), which enables them to deliver the radiation directly to the tumor while protecting the healthy tissues nearby.

We discussed the benefits of MRI-Assisted Radiosurgery used with brachytherapy treatment with Steven Frank, M.D., who developed the Food and Drug Administration-approved positive-contrast MRI marker technology at MD Anderson for prostate cancer treatment.

What is brachytherapy?

Brachytherapy is a type of internal radiation therapy where tiny radioactive seeds are implanted in the body to destroy cancer cells. These seeds are about the size of a grain of rice.

When treating prostate cancer with brachytherapy, the implant is placed directly in the prostate as close to the tumor as possible. This allows us to deliver high doses of radiation directly to the tumor while limiting radiation exposure to healthy tissue.

What is MRI-assisted radiosurgery (MARS)?

MARS is currently the most advanced form of brachytherapy. This modern technique, used for treating prostate cancer, provides more precise delivery of radiation and fewer radiation-related side effects.

MRI-assisted radiosurgery destroys the tumor within the prostate. Radiosurgery is a very precise form of therapeutic radiation therapy where the prostate is not removed.

Before MARS was developed, brachytherapy was done using CT scans and ultrasounds for imaging. However, because the implanted radioactive seeds are difficult to view with conventional imaging, it’s harder to ensure precise placement of the seed, which can influence the effectiveness of the therapy.

So, in 2009, a permanent implantable positive-contrast MRI marker was created for use in prostate brachytherapy to improve quality assurance of the treatment. This marker enabled the use of MRI in treatment planning, delivery, and post-implant assessment and the development of MRI-assisted radiosurgery, also known as MARS.

Now, with the use of MRI to assist in placing seeds in prostate cancer patients, our experts can better visualize the tumor during treatment so we can avoid radiation to surrounding healthy tissues near the prostate.

What is the difference between low-dose and high-dose rate brachytherapy?

Depending on the complexity of the tumor, brachytherapy treatment uses either:

• low-dose rate radioactive seeds, which are implanted permanently, or 
• high-dose rate radioactive seeds, which are temporary. 

Both are done as outpatient procedures, with little downtime for patients.

How does MARS work?

MRI is used at every step of the quality assurance process from diagnosis, treatment simulation, contouring, treatment planning, treatment delivery, and assessment afterward. MRI markers allow physicians to accurately locate the implanted seeds within the prostate. This helps make the delivery of the internal radiation treatment very precise.

Which cancer patients are most likely to benefit from MARS brachytherapy?

MARS brachytherapy has been used to treat low-risk, intermediate-risk, and high-risk localized prostate cancer for several years. Doctors will perform a physical exam and imaging exam to evaluate current urinary symptoms and determine if this is the best treatment approach for each patient.

What does the treatment regimen look like for patients who receive MARS?

Patients with early-stage disease are treated with MARS brachytherapy alone to deliver precisely targeted radiation to the tumor.  For patients with more advanced-stage disease, the MARS implant takes place after the patient completes four weeks of external beam radiation treatment with either proton therapy or intensity-modulated radiation therapy in combination with hormone therapy. This is done to increase the radiation dose to the tumor, with the goal of reducing the risk of the disease progressing.

What are the benefits of MARS?

By using MRI at each step of the MARS treatment process, our experts can better see the tumor and the surrounding organs to ensure very accurate placement of the seeds. This will help to optimize cure while minimizing both acute and long-term side effects after treatment. Without MARS, the external urethral sphincter cannot be seen with standard CT or ultrasound imaging.

What are the side effects associated with MARS?

Side effects from MARS are minimal. Most patients return to normal activities the day after the procedure. After treatment, patients can return to normal sexual activity. Incontinence is rare, but some patients may experience temporary urinary side effects. These include burning, frequent or urgent need to urinate. These side effects can be managed with medication and typically resolve a few months after treatment.

Disclosure: Steven Frank, M.D., and MD Anderson Cancer Center licensed IP related to MARS to C4 Imaging, LLC, and Dr. Frank holds equity in the company and currently serves as the Chairman of their board of directors.

Request an appointment at MD Anderson online or by calling 1-877-632-6789.