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COVID-19 Vaccine Third Dose

September 1, 2021

As COVID-19 rates continue to rise throughout the country, we have a new tool in our arsenal to combat the spread: a third dose of vaccine for those with moderately to severely compromised immune systems, or “immunocompromised” individuals. On August 13, the Centers for Disease Control and Prevention (CDC) began recommending an additional dose of the Pfizer or Moderna vaccine for those in this category who had received an mRNA vaccine. Please note that additional vaccine doses are not recommended for any other group at this time.

Immunocompromised individuals are those who have a disease or are taking a drug that weakens their immune system and makes it harder for them to fight infections.

Those who fall into the category of moderately to severely immunocompromised make up about three percent of the U.S. population and are at high risk for severe illness if they contract COVID-19.

According to the CDC, the recommendation for an additional vaccine dose is based on studies showing that some people with medical conditions that weaken their immune systems do not respond as well to two doses of the mRNA vaccines when compared to those without these conditions. The idea, therefore, is that a third dose will increase the immune response.


To be eligible for a third dose, a person must:

  • Be at least 12 years old
  • Have received a second dose of either the Pfizer or Moderna vaccine at least four weeks (28 days) ago
  • Be considered moderately to severely immunocompromised

Moderately to severely immunocompromised individuals include those who:

  • Are undergoing active treatment for cancer
  • Have received an organ transplant and are taking immunosuppressive therapy
  • Have received a stem cell transplant within the past two years
  • Have a moderate or severe primary immunodeficiency syndrome
  • Have advanced or untreated HIV
  • Are undergoing active treatment with a high dose of corticosteroids or other drugs that weaken the immune system

While this is not a complete list, it should be noted that conditions such as diabetes, obesity and heart or lung disease do not automatically make someone eligible for a third dose. Anyone who has an immunocompromising condition or is taking drugs that weaken their immune system should discuss with their doctor whether they should get a third dose.

As a first step, we recommend checking out COVID-19 Vaccine Third Dose Eligibility Criteria, NYC Test & Trace’s “cheat sheet” for determining if you or a loved one qualifies for a third dose.

Frequently asked questions

With this situation evolving so rapidly, it’s understandable to have any number of questions. Answers to many of these question may be found in NYC Test & Trace’s What You Need to Know: COVID-19 Vaccine – Third Dose for Immunocompromised Individuals and the NYC Health Department’s COVID-19 Vaccines: Third Dose for People Who Are Immunocompromised, and below we addresses a few of the most commonly asked ones.

Is getting a third dose of the vaccines safe?

Yes. All of the authorized COVID-19 vaccines have been proven to be safe, and the Food and Drug Administration (FDA), CDC and independent experts have determined that the benefits of getting a third dose outweigh any known or potential risks for moderately to severely immunocompromised individuals.

What about people who got the Johnson & Johnson vaccine?

An additional dose for people who are immunocompromised and received the Johnson & Johnson COVID-19 vaccine has not been authorized by the FDA at this time. Additional information is expected to be available soon.

How does getting a third dose work?

Getting a third dose is largely similar to getting the first two. It is available wherever vaccinations are given, such as City-run vaccination sites, pharmacies, hospitals, community health centers and doctors’ offices.

You do not need to get your third dose at the same site you got your previous ones. Just visit nyc.gov/vaccinefinder or call 877-VAX-4-NYC (877-829-4692) and look for a site that offers the same vaccine brand (Pfizer or Moderna) as you had for your first two doses. You can also schedule a free in-home vaccination by visiting nyc.gov/homevaccine or calling the number above.

What is the difference between the third shot and a booster shot?

There has been some confusion as to whether to call the recommended third dose for immunocompromised individuals a booster shot. According to the CDC recommendation, the third mRNA vaccine dose is considered a continuation of the primary series, rather than a booster, and is intended to help immunocompromised individuals build up as much immunity as possible against the virus.

A booster shot is an additional dose of a vaccine administered periodically to help sustain the body’s immune response, i.e., to “boost” one’s immunity. An example is the tetanus shot that is recommended for adults to get every 10 years.

In terms of the COVID vaccine, at this time the CDC has not made any changes to the vaccination schedule or quarantine guidance for the general public, and this is true for New York City as well.

Staying informed

With the COVID-19 news seeming to change daily, it’s best to consult trusted, reliable sources for the most up-to-date scientific information, such as the below pages from the CDC, NYC Health Department, Kaiser Health News and Yale University School of Medicine, which are updated regularly

Staying safe

The NYC Test & Trace Corps is doing all it can to stop the spread of COVID-19 in New York City.

Our contact tracing workforce has served the city proudly and with distinction since June of 2020, and is one of the main reasons that NYC is not seeing the same kind of surges in COVID cases and hospitalizations that are overwhelming cities and states around the country.

Another critical reason behind New York City’s relative success in combatting the virus is its high vaccination rates. Each passing day brings more evidence that the COVID vaccines are extremely effective at preventing severe illness, hospitalization and death. In NYC, approximately 97 percent of those hospitalized with COVID are unvaccinated. The effectiveness of the vaccines along with the fact that a majority of New Yorkers are vaccinated are helping prevent us from returning to the dire situation we were in last year, when our ICUs were at capacity and every day was another immeasurable tragedy of lost loved ones.

Today, as we watch other parts of the country suffering these same tragedies, each and every one of us must be steadfast in our resolve to stay New York Strong by doing everything we can to stop the spread of COVID.

NYC Test & Trace therefore asks all New Yorkers to be our partners in fighting this pandemic by:

If you have been in close contact with someone who tests positive for COVID, they may provide Test & Trace with your information so a contact tracer can reach out to you to let you know you’ve been exposed and provide you with resources and information on what you should do next.

A call from an NYC contact tracer will come from one of the following: “NYC Test & Trace Corps,” “NYC COVID Test,” 212-540-#### or 212-242-####. If you want, you can ask to validate your tracer. They’ll give you a code to type into testandtrace.nyc to prove who they are.

Participating in the contact tracing process is one of the most important things you can do to help stop the spread of COVID in your community and your city. So please, if you see a call from one of the above caller IDs, answer the call!

And remember: The best and easiest way to protect you, your loved ones, your community and your fellow New Yorkers from COVID is to get vaccinated.

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