Health and Disease

Johnson & Johnson Vaccine Update

On February 27, the Food and Drug Administration approved Johnson & Johnson’s single dose COVID-19 vaccine. Johnson & Johnson now plans to ship approximately 20 million doses by the end of March. What do we know about this vaccine?

By Afifa Zahid

Published 9:49 PM EST, Thurs March 18, 2021


As vaccine distribution ramps up  in the United States, the end of the COVID-19 pandemic becomes more feasible to imagine. Additionally, President Joe Biden’s goal to vaccinate the entire country within his first 100-days becomes much easier, as this J&J will alleviate the distribution pressure and help many American’s get off the vaccine waitlist.

Perhaps one of the most notable differences between the Johnson & Johnson vaccine and the vaccines currently available (Pfizer and Moderna) is Johnson & Johnson’s lower efficacy rate. In the latest clinical trial, the vaccine had a 72% efficacy rate, a notable difference from both  the Pfizer and Moderna vaccines that had a 95% efficacy rate. However, this statistic does not tell the whole story. The Johnson & Johnson vaccine demonstrated an overall 85% efficacy rate against severe forms of COVID-19 cases and a 100% efficacy rate against hospitalization and death, just like the Pfizer and Moderna vaccines.

Regardless, this isn’t a numbers game. It’s more important to acknowledge the fact that we now have three vaccines. In response to the FDA approval of the new vaccine, Dr. Anthony Fauci stated “ ‘Rather than parsing the difference between 94 and 72, accept the fact that now you have three highly effective vaccines. Period.’ “. 

The Johnson & Johnson Vaccine Mechanism of Action 

A significant differentiator for the Johnson & Johnson vaccine is that it is a single dose; while both vaccines currently available are double dose vaccines. Furthermore, the Johnson & Johnson can be refrigerated for up to three months, between temperatures of 36°F and 46°F. The Pfizer and Moderna vaccines, on the other hand, have to be used shortly after it comes out of refrigeration. Further complicating vaccine storage, the Pfizer vaccine must be stored in dry ice for up to only 5 days. The Moderna vaccine has to be stored at -94°F . 

Now that the key differences between the J&J vaccine and double doses have been discussed, the J&J vaccine’s mechanism of action can be better understood. The coronavirus is covered with spiky protein structures, that the virus uses to latch onto cells inside the body. Specifically, the virus attaches to receptors on healthy cells, especially those in our lungs. Once inside, the coronavirus hijacks healthy cells and takes command, eventually killing healthy spells.

The Johnson & Johnson vaccine is based on the virus’s genetic code for building proteins. While the Pfizer and Moderna vaccines focus on single-stranded RNA, the site of protein development, the Johnson & Johnson vaccine uses a double-stranded DNA mechanism. 

The coronavirus spike protein was added to another virus, Adenovirus 26. Adenoviruses cause flu-like symptoms or colds. However, by using a modified version of this virus, it could enter the cells but not replicate or cause an illness. Immediately after the vaccine is injected into one’s arm, the adenovirus latches onto proteins found on the surface of healthy cells. As the cell completely engulfs the virus and pulls it inside, the adenovirus then travels into the nucleus. Here, the cell reads the gene for the coronavirus spike protein and its copied into a molecule called mRNA, messenger RNA.

The mRNA then leaves the nucleus and begins to assemble spike proteins. The spiked proteins produced by the cell travels to the surface of the cell where the either cling to the surface or are broken up into fragments. The spikes and spike fragments are then recognized by the immune system, programming the immune system to attack spiked proteins – like those on the surface of the coronavirus. 

Additionally, the adenovirus also triggers the cell’s alarm systems, sending out a warning to nearby cells to activate immune cells. Allowing the immune system to initiate a stronger response against spike proteins, such as those found on the coronavirus. 

Further, B cells, a type of immune cell found in the body, can also bump into the coronavirus spikes on the surface of vaccinated cells or free-floating fragments. These B cells then attach themselves to the spike proteins. Once they’re activated by helper cells, like T cells, the start to introduce antibodies that target the spike protein. These antibodies latch onto coronavirus spikes and mark the virus for destruction as well as prohibit the spikes from attaching to other cells. 

It’s also important to become familiar with the effects associated with the J&J vaccine. The most common effects are pain at the injection site, headaches, and flu-like symptoms. While these side effects are also common in people who received either the Pfizer and Moderna vaccines., it’s notable that in clinical trials fewer people experienced side effects, relative to those who took one of the mRNA vaccines. These side effects are common; approximately 55% of people who participated in J&J clinical trials experienced these symptoms. Though, these side effects resolve in an average of two days. 


While the effectiveness and efficacy of the vaccine is questioned, due to its expedited development process, one must remember that these vaccines are the result of decades of research on adenovirus and SARS. And they’ve been proven effective after several clinical trials. They’re safe. So, as soon as you become eligible to take the vaccine, do it. You’d not only be helping yourself, but helping the United States overcome the COVID-19 pandemic.  

Afifa Zahid, Youth Medical Journal 2021


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  2. Press, The Associated. Johnson & Johnson Begins Covid-19 Vaccine Distribution. 1 Mar. 2021,
  3. “We Thought It Was Just a Respiratory Virus.” We Thought It Was Just a Respiratory Virus | UC San Francisco, 2 Mar. 2021, 
  4. Weiland, Noah, and Sharon Lafraniere. F.D.A. Clears Johnson & Johnson’s Shot, the Third Vaccine for U.S. 27 Feb. 2021, 
  5. Corum, Jonathan, and Carl Zimmer. “How the Johnson & Johnson Vaccine Works.” The New York Times, The New York Times, 18 Dec. 2020,
  6. Johnson & Johnson.
  7. Kollewe, Julia. “From Pfizer to Moderna: Who’s Making Billions from Covid-19 Vaccines?” The Guardian, Guardian News and Media, 6 Mar. 2021,
  8. Piper, Kelsey. “We’re Not Looking at the Most Important Vaccine Statistic.” Vox, Vox, 11 Feb. 2021, 

By Afifa Zahid

Hi my name is Afifa Zahid and I am a senior at Bard High School Early College Manhattan and I'm interested in neurology .

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