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If you are 50 years or older, you are eligible for a second booster shot at least 4 months after your first booster. Regardless of which shots you initially received, your second booster must be an mRNA COVID-19 vaccine (Pfizer-BioTech or Moderna). The CDC is also suggesting a second booster for those who are moderately or severely immunocompromised.  Click here to read more about the CDC’s latest updates on COVID-19 vaccination and booster eligibility.

Who Is Moderately or Severely Immunocompromised?
Many conditions and treatments can cause a person to be immunocompromised (having a weakened immune system). People are considered to be moderately or severely immunocompromised if they have:

  • Been receiving active cancer treatment for tumors or cancers of the blood
  • Received an organ transplant and are taking medicine to suppress the immune system
  • Received a stem cell transplant within the last 2 years or are taking medicine to suppress the immune system
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids or other drugs that may suppress their immune response

All patients and visitors must have an appointment to enter the office. If you have a request or concern outside of your office visit, please call the office or use the Patient Portal. To read more about this policy, click here.


Starting 1/19/2022, residential households can order one set of 4 free at-home tests from USPS.com. Click here for more information.

Starting 1/15/2022, private insurers are required to reimburse up to 8 at-home test kits per month. The kits will either be covered at the time of purchase or reimbursed by submitting a claim to their insurer. Check with your insurance company for details and be sure you save your receipts. To read more about this, click here.


Currently, Greenhouse is not offering the COVID-19 vaccine.  Larger health systems and pharmacies that have the space to meet the storage requirements of the vaccine and monitor patients after the vaccine is administered are offering the vaccine. It is safe to go to your local pharmacy to receive your vaccine, which is administered by a pharmacist. To find a Vaccine site near you, you can also visit www.vaccines.gov. If you have received the vaccine, we recommend following the CDC’s guidelines for staying up to date with your vaccines.


Covid Testing Sites
Quarantine and Isolation Guidelines
Caring for Someone at Home
City of Philadelphia COVID-19
Information for Travelers
Vaccine Card Dos and Don’ts


Masks must be worn the entire time you are in the office.  If you don’t think you will be able to wear a mask correctly (covering your nose and mouth) the entire time you are in the office, you will need to schedule a telehealth appointment.


Since the beginning of the COVID-19  pandemic, Greenhouse Internists has strived to keep our patients and employees safe by implementing numerous safety measures, such as allowing more time between patient visits to ensure social distancing and time for disinfecting exam rooms, screening all patients before entering the office, offering telehealth appointments, and requiring an appointment to enter the office.  To review all COVID-19 – related office information and policies, click here.

Elizabeth Fabens

Dr. Elizabeth Fabens grew up in Ohio and went to college at Brown University, graduating in 1976. She worked in the health care field for several years and then started medical school at the University of Massachusetts Medical School in Worcester, Mass in 1981. She moved to Philadelphia in 1985 to start her residency in Internal Medicine at The Medical College of Pennsylvania Hospital. After residency, she worked for several years at one of the city health centers in Germantown.
Dr. Fabens previously worked as a medical consultant at the Abbottsford Health Center and has also worked at the Medical College of Pennsylvania AIDS Clinic.
Dr. Fabens has been at Greenhouse Internists since June, 1990.She is Board Certified in Internal Medicine and has an additional qualifying certificate in Geriatrics. 

Dan Peterson

Dr. Daniel Peterson graduated from Bucknell University and Penn State University School of Medicine. He completed his internship at Mary Imogene Bassett Hospital in Cooperstown, New York, and his residency at St. Luke’s-Roosevelt Hospital Center in Manhattan.
He remained at St. Luke’s-Roosevelt as teaching faculty and in a part-time private practice. He directed the resident curriculum in Evidence Based Medicine and was the director for the institution’s participation in the Academic Chronic Care Collaborative.
 Dr. Peterson is Board Certified in Internal Medicine. He enjoys riding his bike on the Wissahickon trails, reading biographies, and spending time with his family.

Tryphena Hsi, CRNP, joined Greenhouse in March 2020.  She has worked as a Nurse Practitioner for over 7 years and has much experience in primary care and women’s health.  Most recently she practiced at Covenant House Health Services, where she provided primary care services to adult and geriatric patients with multiple chronic illnesses. Tryphena is passionate about patient education and empowering patients to make positive health changes. Tryphena is available to see patients for urgent and follow up needs in the office or by virtual visit.

Suzannah Maynard, CRNP, joined Greenhouse in November 2021. Sue grew up on her family’s multigenerational family farm in Midcoast Maine. After undergraduate and graduate degrees in Engineering, and working in the field for almost a decade, she realized a lifelong interest in caring for people and transitioned into healthcare. Since receiving her undergraduate and graduate degrees in Nursing she has worked with patients across the lifespan from newborns to patients well into their post-retirement lives. She also serves as a clinical adjunct in the graduate nursing programs at Thomas Jefferson and the University of Pennsylvania. In her free time she can be found knitting, reading, traveling, or traveling via food.