Single Dose Johnson & Johnson Vaccine Works Well but May Be Falling Short in Supply

February 25, 2021

From Ahvie Herskowitz, MD

Efficacy Data for FDA Approval

Johnson & Johnson’s vaccine could be authorized by the FDA as early as this Saturday depending upon votes from the vaccine advisory panel tomorrow. Vaccine efficacy in the United States was 72%, and 64% in South Africa, which compares very favorably with other vaccines. The data still shows strong protection against severe COVID-19 cases and deaths, with a possible reduction of virus transmission and prevention of infection (74% effective against asymptomatic infections in small numbers of patients tested for antibodies).

With the FDA’s first technical analysis this week of the Phase 3 trial, there have been no reports of severe allergic reactions like anaphylaxis, thus they claim that the Johnson & Johnson vaccine is safe with relatively mild side effects.

Familiar Vaccine Technique

The model of using a modified adenovirus for holding the genes to build coronavirus spike proteins is a familiar technique to vaccines: the injection of the vaccine releases the adenovirus to push the genetic instructions into the nucleus of the human cell which is copied into messenger RNA to leave the nucleus and be translated to building the coronavirus spike proteins.

Distribution following FDA Approval

The United States has agreed to buy 100 million doses of the Johnson & Johnson vaccine by June 2021. While Johnson & Johnson expected to produce 12 million doses by the end of February, only 2-4 million doses are estimated ready for shipment by the end of the week pending FDA authorization, and concerns over meeting their 100 million dose target by June 2021 remain.

Disclaimer: This information is formulated as my opinion, and I recommend that any individual speak with their primary doctor about their own personal health concerns and questions about COVID-19 vaccinations.


Supportive Data for Johnson & Johnson Vaccine

New Analyses Show Johnson & Johnson’s One-Dose Vaccine Works Well

(Updated 2/24/21 at 5:00AM PST)


  • FDA post on Wednesday 2/24/21: “strong protection against severe disease and death from COVID-19 and may reduce spread of virus by vaccinated people.”
  • FDA could authorize Johnson & Johnson vaccine as early as Saturday 2/27/21 depending upon vaccine advisory panel on Friday 2/26/21.

Efficacy Rate

  • 72% overall efficacy rate in United States and 64% in South Africa (7 points higher than earlier data released on 1/29/21).
  • 86% efficacy against severe forms of COVID-19 in United States and 82% against severe disease in South Africa.
    • Novavax – 49% efficacy in South Africa.
    • AstraZeneca – “found it did not offer much protection at all.”
  • 42.3% (lower) efficacy for people over 60 who had risk factors ie: heart disease or diabetes — but FDA says this figure came with “large amount of statistical uncertainty.”
  • Johnson & Johnson has lower efficacy rate than Moderna + Pfizer-BioNTech, which are both around 95%.


  • Vaccine is “safe, with noticeably milder side effects than Pfizer and Moderna, and without any reports of severe allergic reactions like anaphylaxis.” (FDA’s first technical analysis of the 45,000 people clinical trial).

Phase 3 Trial Demographics

  • Black, Hispanic and white volunteers, across different ages.
  • 45,000 people enrolled.

Prevention of Infection and/or Transmission

  • Moderna: “some hints” that vaccinated people were less likely to develop asymptomatic infection.
  • Astrazeneca: reduced asymptomatic infections by 50%.
  • Johnson & Johnson: 74% efficacy against asymptomatic infection.
    • This is determined by checking for COVID-19 antibodies 71 days after vaccine or placebo is given to the individual — FDA noted “small number of volunteers…uncertainty about interpretation.”


  • Stored at normal refrigeration temperature for at least 3 months.
  • Estimated 4 million doses would be ready for shipment after FDA authorization (lower than original 12 million pledge by end of February).
    • White House says only around 2 million doses would be available by next week.
    • Johnson & Johnson has contract with United States to deliver 100 million doses by end of June

Other Sources


How the Johnson & Johnson Vaccine Works

(updated 2/24/21)

COVID-19 vaccines are based on the virus’ genetic instructions for building coronavirus spike proteins- these proteins are used to enter the human cells.

Regarding the Johnson & Johnson vaccine technique, DNA is not as fragile as RNA and the DNA inside the adenovirus is protected by the tough protein adenovirus coat — this is why this vaccine can be kept refrigerated for up to 3 months.

Adenovirus-Vectored Vaccine Technique

  1. Johnson & Johnson’s vaccine uses double-stranded DNA to store the genetic instructions.
  2. The DNA that holds the genetic instructions is added to a modified Adenovirus (Adenovirus 26) that enters human cells but cannot replicate inside them or cause illness.
  3. Once the vaccine is injected, the modified adenoviruses are engulfed by human cells and make their way to the nucleus of the cell.
  4. The adenovirus pushes the DNA into the nucleus of the cell so that the genetic information for building coronavirus spike proteins is read by the cell and in turn copied into messenger RNA (mRNA).
  5. mRNA leaves the nucleus, and the human cell’s molecules read the mRNA sequence to use that to build coronavirus spike proteins.
  6. Proteins form spikes that migrate to the human cell’s surface and stick out from the membrane, or some are broken up into fragments to also present on the surface, both of which are recognized by the body’s immune system. The immune system also turns on alarms that release warning signals to activate immune cells nearby — this is what makes the Johnson & Johnson vaccine trigger the immune system to react more strongly to the spike proteins.

Single Dose Administration

  • Antibodies and killer T cells should drop in count months after a person is vaccinated, but the immune system should retain memory B and T cells to keep information about the coronavirus for long-term recognition of the virus.
  • The phase 3 trial results have not yet been released, so the FDA is unsure of how effective 1 dose of the Johnson & Johnson vaccine will be for how long.

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About Ahvie Herskowitz, MD

Dr. Herskowitz’s extensive training includes a medical degree from The Albert Einstein College of Medicine, residencies in Anatomic Pathology and Internal Medicine, and Fellowship training in Cardiology at The Johns Hopkins Medical Center. During his 12 years at Johns Hopkins, he became Associate Professor of Medicine and Immunology and Molecular Microbiology and led a research team in the study of molecular and immunological mechanisms of inflammation, autoimmunity, ischemia, heart transplantation rejection and congestive heart failure.

Dr. Herskowitz’s latest academic appointment was as Clinical Professor of Medicine at UC San Francisco. To learn more about Dr. Herskowitz, you can read it bio here.


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