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The Janssen (Johnson & Johnson) COVID-19 Vaccine

On February 24, 2021, the Food and Drug Administration (FDA) found the third COVID-19 vaccine, developed by Johnson & Johnson pharmaceutical arm Janssen, to be safe and effective against the coronavirus. The Janssen vaccine was 85 percent effective in preventing severe illness and 100 percent effective in preventing hospitalization and death, according to the Washington Post.

Because the Janssen vaccine only requires a single shot and can be stored in a refrigerator instead of a freezer, the emergency use authorization of this vaccine, which was authorized for early use as of February 27, 2021, provides a viable alternative to the Pfizer and Moderna vaccines. In this blog, we’ll take a look at the Janssen vaccine and how it compares to the Pfizer and Moderna vaccines.


Vaccine Types


Both the Pfizer and Moderna vaccines are mRNA nucleic acid-based, while the Janssen vaccine is a non-replicating viral vector. The mRNA technology uses genetic instructions to tell a person’s cells to make a piece that looks like the spike protein unique to SARS-CoV-2 (the virus that causes COVID-19). Those proteins trigger an immune response and build immunity.

The Janssen vaccine uses a different vaccine technology than Pfizer’s or Moderna’s mRNA vaccines. The tough protein coat of the weakened cold virus (adenovirus) helps protect the DNA genetic instructions inside. Though the virus cannot do any harm in the body, once it enters a person’s cells, those cells read the genetic instructions to make a protein that looks like the spike protein. The immune system sees the proteins and makes antibodies against them to protect the person from the virus. Both vaccine technologies are safe and effective and cannot infect the person with COVID-19.


Storage and Dosage Considerations


While the Pfizer and Moderna vaccines must be stored frozen at ultralow temperatures, the Janssen vaccine can last three months when kept at normal refrigerator temperatures (2–8OC). The Janssen vaccine can be stored at -20OC for two years. After first use, the vaccine can be stored at 2–8OC for six hours and at room temperature for two hours.

While the Pfizer and Moderna vaccines require two injections administered several weeks apart, the Janssen vaccine requires only a single intramuscular (IM) dose. Each vial of the vaccine holds five doses. With only a single injection needed and the fact that the vaccine remains stable at higher temperatures, the Janssen vaccine offers a potentially more cost-effective vaccine option.


Clinical Trials


Two randomized, double-blind, placebo-controlled clinical studies launched in September and November 2020 compared the efficacy of a single-dose Janssen vaccine against a two-protocol (day 1 and day 57). The ENSEMBLE study was conducted in eight countries across three continents; the Janssen vaccine was tested in a diverse and broad population, including 34 percent of participants over the age of 60. In this trial, 41 percent of participants had comorbidities associated with an increased risk for progression to severe COVID-19, including:

  • Obesity – 28.5%
  • Type 2 Diabetes – 7.3%
  • Hypertension – 10.3%
  • HIV – 2.8%

Primary outcomes evaluated post-vaccinated COVID-19 cases (day 15 and day 29) and were counted if seropositive (PCR) plus evidence of:

  • Pneumonia; deep vein thrombosis; difficulty breathing; abnormal oxygen saturation or a respiratory rate equal to or greater than 20; or two or more signs or symptoms suggestive of COVID-19, such as cough, sore throat, fever, or chills (moderate disease)
  • Clinical signs at rest indicative of severe systemic illness, respiratory failure, shock, significant organ dysfunction, hospital intensive care unit admission or death (severe illness)



At day 29, the Janssen vaccine revealed the following:

  • 100% effectiveness against hospitalization and death
  • 85% effectiveness against severe disease
  • 66% overall effectiveness against moderate and severe disease
    • 72% in the United States
    • 66% in Latin America
    • 57% in South Africa

In addition, the Janssen vaccine displayed the following results:

  • Efficacy trends increased over time
  • No cases reported post day 49
  • Results consistent across age and race
  • B.1.351 lineage represented 95% of cases in South Africa
  • Fever rate 9% overall, grade 3 fever 0.2%
  • No anaphylaxis observed
  • Five deaths in placebo group related to COVID-19



With only one dose required and ability to be shipped and stored at higher temperatures, the Janssen vaccine offers a potentially more cost-effective solution in the vaccine toolbox for protecting more individuals around the world against COVID-19.

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[1] Ryan, Maggie. “FDA Finds the Johnson & Johnson Corona Virus Vaccine Safe and Effective Against COVID-19.” Pop Sugar. February 24, 2021. Accessed February 25, 2021.

Posted: Thursday, March 11, 2021

Tags: COVID-19, Blog