Johnson & Johnson COVID Vaccine Review

It is the end of February, cases seem to be plateauing in many areas, and we now have approval for a third COVID vaccine.  As I did in my previous articles on the Pfizer and Moderna vaccines, I will discuss the use of this specific vaccine, dosing, efficacy, and side effect profiles.  I will NOT be getting into the design of the study used to get this data, as that may be a little boring.

How Is This One Different From the Others?

It seemed like mRNA vaccines were all the rage when it came to managing COVID vaccinations.  However, this vaccine utilizes an altered virus (in this case one called Adenovirus) in which the virus can stimulate an immune response, however it can NOT replicate within cells, thus preventing illness.  The virus is encoded with the spike protein found on SARS-CoV-2, and expression of this allows for an appropriate immune response. 

Of note, this specific altered Adenovirus strain has NOT been used in other mainstream vaccines.  However, it has been used in other vaccines not accustomed to are geographical area.  Its use in the Ebola vaccine as well as those currently in ongoing vaccine trials not related to COVID has shown a favorable side effect profile in using this vehicle for inoculation. 

Photo by Karolina Grabowska on


The mRNA vaccines are currently a 2-dose series, whereas this vaccine is a single shot.  The benefit to this is that you have a quicker route to being protected, usually 2 weeks after this inoculation.  The mRNA vaccines are not considered fully active until 2 weeks after the 2nd shot.  They are currently doing studies on the Johnson & Johnson vaccine as a 2-dose series to see if its efficacy/effectiveness improves.


One thing to remember with this trial compared to the two mRNA trials is that the study data and design were performed when COVID rates were higher.  Thus, this could influence the efficacy due to the higher exposure potential of the trial participants in the J&J trial when compared to Moderna or Pfizer’s vaccine trials.  The other difference is that J&J’s vaccine studies were looking at preventing moderate-to-severe infections of COVID, where the designs for the mRNA vaccines were looking at all infection types.

Overall, the J&J vaccine trials (performed in the US, South Africa, and South America) compiled together showed an efficacy of around 66% with no difference in age groups.  The study performed in the United States showed an efficacy of 72%, whereas the one in South America was 66% and South Africa was 57%.  This may be due to the variants in these regions at the time. 

Components of the Vaccine

I forgot to mention this in the previous vaccine articles, but all of these vaccines have very minimal components outside of the spike protein vector. There are NO animal protein products within this vaccine to react to. The other components include citric acid monohydrate, trisodium citrate dihydrate, ethanol, 2-hydroxypropyl-Beta-cyclodextrin, polysorbate 80, sodium chloride, sodium hydroxide, and hydrochloric acid.

Deaths During the Trial

Let’s cover this first.  As I mentioned in previous articles, deaths occur all the time in everyday life.  This continues during vaccine trials, regardless if the participants received the vaccine or placebo.  In the J&J trials, there were 19 total deaths (3 in the vaccine group, 16 in the placebo group). 

  • Seven of those patients were in the PLACEBO group, all were in the South Africa trial, their ages ranged from 49-68, and these deaths were all attributed to being a COVID related death. 
  • Other placebo group deaths consisted of pneumonia (2), suicide (1), accidental overdose (1), heart attack (1), malaise (1), unknown causes (3)
  • 2 vaccine trial deaths were related to respiratory infections not related to COVID, and the other was also unrelated to the vaccine
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Severe Adverse Events

  • These are events that occur during the trial that are considered severe but not fatal.  These MAY or MAY NOT be associated with the vaccine
  • 0.4% of the vaccine group and 0.4% of the trial group reported this
  • Most common complaint was appendicitis (6 in the vaccine group, 5 in the placebo group)
  • Of the other SAE’s, 3 were seen as related or likely related, 2 as possible, and 1 as indeterminate in regards to the vaccine
    • Related events consisted of one case of radiculitis brachial (injection site pain), one case of post vaccine syndrome (reactogenicity) that resolved, and 1 likely case of hypersensitivity reaction post vaccination
    • 1 possible cause of Guillain-Barre Syndrome and 1 possible cause of pericarditis (could not be excluded that vaccine was the cause)
    • 1 indeterminate case of deep vein thrombosis
  • There was a balanced report of Bells Palsy on both the vaccine and placebo group (2 in each group), but I wanted to mention this as I know this has been covered in other COVID vaccine trials as well

Side Effects

 When reporting side effects, there are several categories to consider.  These consist of local adverse reactions, related to the shot into the arm itself and how the body reacts; Systemic Adverse reactions like fevers, body aches, and fatigue are the other category. 

Localized Adverse Events

  • 50.2% in vaccine group vs 19.4% in the placebo group. 
    • Most common in order were injection site pain, erythema (redness), and swelling.
  •  More common to be found in the younger age range (18-59 years old) when compared to the older group (60+ years).
  • Median time for symptoms to occur was 2 days
  • Median duration of symptoms was 2 days for pain and erythema and 3 days for swelling
  • Rates of localized adverse reactions were similar in those who had a negative COVID test prior to trial when compared to those with a positive test prior to the trial

Systemic Adverse Reactions

  • 55.1 % in vaccine group vs 35.1% in placebo group
    • Headache, fatigue, muscle aches, nausea, and fever were the main symptoms in order of occurence
  • More common in the younger are range (18-59 years old) than the older age range (60+ years old)
  • Median duration for symptom onset was 2 days. 
  • Median duration of symptoms was 2 days for fatigue and headache, 1 day for nausea and fever. 
  • ~1% of patients with fatigue and body aches lasted more than 7 days, 0.7% for headaches, and 0.3% for nausea.  No fevers lasted longer than 7 days after vaccination
  • Rates of systemic adverse reactions were similar in those who had a negative COVID test prior to trial when compared to those with a positive test prior to the trial


  • The trial did NOT include pregnant participants, and those who became pregnant during the trial are being further monitored
Photo by Ann H on


At first glance, it is easy to compare this vaccine to the mRNA vaccines.  When one has an efficacy record in the 60’s whereas the mRNA’s are in the 90’s, it would be easy for people to quickly judge this vaccine as being “less superior” to its counterparts.  However, the trials were not performed in the same setting in terms of COVID infection rates, nor were the trials designed in a similar fashion.  We also must remember that initially we were accepting any vaccine with a >50% efficacy rating as an emergency use, so this one checks the box. 

Ultimately the purpose of the vaccine is to prevent severe infection and death, which the J&J vaccine did.

Its single dosing regimen may make it more accessible for some people, but I will be interesting to see how their 2-dose trials turn out. 

For me, I would take whatever vaccine is available to me.  I can not appropriately determine if one vaccine is truly superior to another at this time.  We may know more in the next year, but at this point if your state/doctor’s office/health department only has 1 option for you, I would take what is available. 

Imperfect Dad, MD

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