Immunocompromised people have a reduced ability to fight infections and are more vulnerable to severe COVID-19. That is why the U.S. Centers for Disease Control and Prevention (CDC) is recommending that people with moderately to severely compromised immune systems receive an additional dose of the Pfizer-BioNTech or Moderna vaccine.

In this Q&A, Meenakshi Rana, MD, Associate Professor of Medicine (Infectious Diseases) at the Icahn School of Medicine at Mount Sinai, and the Director of Transplant Infectious Disease, explains why immunocompromised people, who make up almost three percent of the U.S. population, should get this third vaccine dose and why it is important to take other protective measures.

What did the CDC recommend?

The CDC and the Advisory Committee on Immunization Practices took an important action to prevent COVID-19 infection in our immunocompromised population and among transplant recipients. They now recommend that people who are moderately to severely immunocompromised receive an additional dose of an mRNA COVID-19 vaccine, either Pfizer or Moderna, at least 28 days after the completion of the initial series. The Food and Drug Administration (FDA) now allows for the additional dose for these people as well.

To be clear, this is not considered a booster dose. A booster dose is given to a patient whose immunity to the vaccine may have waned over time. This is considered an additional dose, given to immunocompromised patients to improve their initial response to the vaccine series. These patients are essentially receiving a three-dose mRNA vaccine series instead of a two-dose series.

Who is considered immunocompromised and should get the third dose?

Meenakshi Rana, MD

Immunocompromised patients are a very large and heterogeneous group. For the purposes of an additional COVID-19 vaccine, the CDC has defined a specific moderately to severely immunocompromised group, which includes:

• Patients who have been receiving active cancer treatment for tumors or cancers of the blood
• Patients who had a solid organ transplant, such as a heart, lung, liver or a kidney, and currently take immunosuppressive medications
• Patients who had a bone marrow transplant within two years or had a bone marrow transplant and are currently taking immunosuppressive therapy, or patients who receive CAR T-cell therapy.
• Patients who have advanced or untreated HIV
• Patients who have another medical condition that require high-dose steroids or immunosuppressive therapy for that medical condition

If you think you fall within this category, it’s important that you speak to your physician to determine if you are eligible for an additional dose of mRNA COVID-19 vaccine.

Why is the CDC taking this action?

Patients who are considered moderately to severely immunocompromised are more vulnerable to COVID-19. They are more likely to have severe disease, and more likely to be hospitalized with COVID-19. In addition, there has been data suggesting that moderately to severely immunocompromised patients may not have as strong an immune response to the initial COVID-19 vaccine series, and we have seen breakthrough infections in vaccinated immunocompromised patients, occasionally requiring hospitalization. The CDC also now has data suggesting that a third vaccine would be safe.

What should I do if I think I am affected by this action by the CDC?

If you think you are considered moderately to severely immunocompromised, talk to your doctor to see if you are eligible for an additional dose of COVID-19 vaccine. The CDC recommends that you receive a third dose with the same mRNA vaccine. For example, if you received an initial Moderna vaccine series, then you should complete your series with an additional third dose of the Moderna vaccine.

What if I am immunocompromised and I received the Johnson & Johnson vaccine?

When the CDC made this recommendation, they did not have enough data on whether immunocompromised patients who received the J&J vaccine would have an improved response after receiving an additional dose of the same vaccine. For this reason, we are currently awaiting more guidance from the CDC on what to recommend for these patients.

If I am immunocompromised, what else should I do to protect myself?

In addition to receiving an additional dose of an mRNA vaccine, you should continue to practice all those protective precautions that we’ve been discussing: social distancing, hand hygiene, and masking. It’s also very important that all of those around you, your family and your friends, are all vaccinated.

The FDA has also authorized the use of a medication, known as a monoclonal antibody, for what is termed “post- exposure prophylaxis.” That means, if you are exposed to a loved one or family member with COVID-19, this medication can be given to you to prevent COVID-19 and progression to severe disease or hospitalization with COVID-19. You should call your physician to see if you are eligible.

Should I get an antibody test to see if I am eligible for the third dose?

We are not recommending that you get an antibody test for this purpose, because we don’t know what level of antibodies is considered protective. We recommend that if you are considered immunocompromised, you should receive an additional vaccine dose, regardless of antibody response.

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.