The Johnson & Johnson COVID-19 Vaccine: What to Know

Published: March 04, 2021

Michael Parry, MD, Director, Department of Infectious Diseases and Asha K. Shah, MD, MS, Associate Director, Department of Infectious Diseases

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Stamford Health is dedicated to stopping the spread of COVID-19 and keeping you informed about the latest news regarding the vaccine.

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Important update about the Johnson & Johnson vaccine since original publication of this blog:
As of April 13 as per guidance from the CDC and FDA, we have paused administration of the Johnson & Johnson vaccine out of an abundance of caution. 

The Johnson & Johnson COVID-19 vaccine just became authorized for emergency use under the FDA for people 18 and older, and is currently being distributed and becoming available to those eligible in the greater Stamford, CT community.  

Infectious Diseases leadership at Stamford Health weighs in on this highly effective new vaccine and clears up some initial misconceptions.

The myth: There’s no difference in how the Johnson & Johnson vaccine is made or given vs. the Pfizer or Moderna.

The truth:

  • The Johnson & Johnson vaccine is the first of the three authorized COVID-19 vaccines that is offered in a single dose.
  • The vaccine does not need to be kept frozen.
  • The Johnson & Johnson vaccine is an adenovirus (or viral) vector vaccine while both the Pfizer and Moderna vaccines use mRNA technology. "Adenovirus" is the term for common viruses that cause a range of illnesses. 

  • Having an adenovirus vector vaccine means you are injecting a modified version of the adenovirus into your cells which delivers important information in the form of a gene. This results in our cells making a small fragment of the SARS-CoV-2 virus called the spike protein, which triggers an immune response.  Viral vector vaccines do not alter your DNA in any way.  The mRNA vaccines made by Moderna and Pfizer deliver mRNA in a lipid envelope which stimulates cells to make spike protein resulting in the same immune response.  

The bottom line:

The Johnson & Johnson vaccine is made differently and administered on a different timeline than the Pfizer and Moderna vaccines, but stimulates the same kind of immune response to protect you against SARS-CoV-2 infection.

The myth: The Johnson and Johnson vaccine is not as effective as the Pfizer or Moderna, so it’s best if I don’t get it and wait for the next “better ones” to become available. 

The truth:

  • All three vaccines are very effective, ranging from 66% to 95% depending on the population studied. 
  • To put things in perspective, the flu shot, in any given year is only 20% to 60% effective, and still strongly encouraged. 

The bottom line:

The Johnson & Johnson vaccine is a new and effective tool in the fight against the pandemic. It is strongly proven to protect against severe illness, hospitalization and death from COVID-19.  If available, you should definitely not hesitate to get it.

Supply and demand of COVID-19 vaccines in general unfortunately don’t allow for a preferred brand choice.  

The myth: The Johnson & Johnson vaccine is being saved for child care providers in the surrounding Stamford, CT area.

The truth:

  • The Johnson & Johnson vaccine is authorized for use in individuals age 18 and above. 
  • The extent to which it’s available will depend upon manufacturing capacity and federal mandates for its distribution.

The bottom line:

Regardless of the brand, it’s strongly advised to get any COVID-19 vaccine that’s available to you! 


Where can I learn more about the COVID-19 vaccine?

  • If you have specific questions or concerns about getting the COVID-19 vaccine, please have a conversation with your primary care physician.
  • For answers to more questions, and to see if you're eligible for the COVID-19 vaccine right now, visit this page.

Featured Expert/ Author

Infectious Disease, Internal Medicine

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