An Overview of the Johnson & Johnson COVID-19 Vaccine

On February 27 2021, Johnson & Johnson's vaccine against coronavirus disease 2019 (COVID-19) became the third COVID-19 vaccine to receive Emergency Use Authorization (EUA) from the FDA.

The company worked with its pharmaceutical arm Janssen to develop the vaccine under the project names Ensemble and Ensemble 2. The company enrolled participants for its late-stage in September 2020 and tested its vaccine with two different doses.

After a single dose was found to be effective in clinical trials, Johnson & Johnson applied for the EUA for the single dose. It was the first COVID-19 vaccine to be given in one dose in the U.S. and was previously authorized for adults ages 18 and older.

How It Works

Johnson & Johnson's vaccine is a single-dose adenovirus-based vaccine. It is a viral vector vaccine that uses a weakened live pathogen (adenovirus) as the delivery method (vector) for transporting a recombinant vaccine for COVID-19. The vaccine is also sometimes referred to as Ad26.COV2.S.

Recombinant vaccines use a small piece of genetic material from the virus to trigger an immune response. This genetic material for COVID-19 does not replicate in the body. A specific piece of the virus can be targeted, and recombinant vaccines are common and generally safe to use in a large population of people—even those with chronic health problems or who are immunocompromised.

There can be some drawbacks to recombinant vaccines. One example is that booster shots may be required over time. Examples of recombinant vaccines are pneumococcal vaccines and vaccines for meningococcal disease.

The science behind recombinant adenoviral vector vaccines has been around for a long time, but the only commercially available adenovirus-based vaccine is a rabies vaccine for animals. Adenovirus-based vaccines may also pose some problems in that the adenovirus is so common that the vaccine may not be as effective once booster doses are given, or that some people may already have immunity to the virus used in the vaccine.

How Effective Is It?

Johnson & Johnson announced that its single-dose vaccine was 66% percent effective at preventing moderate to severe disease from COVID-19 and 85% effective at preventing severe disease. This effectiveness in the Phase 3 trial was reached 28 days after vaccination.

The trial had a temporary delay in October 2020 when it was paused due to a patient reporting an unexplained illness, although no specific details were provided about what happened due to patient privacy. Regulators determined that the event was not related to the vaccine and the trial was safe to resume.

The efficacy against moderate to severe COVID-19 infection varied by region in the trial. It was 72% in the United States, 68% in Latin America, and 64% in South Africa.

The vaccine was also found to be fully protective against hospitalization and death, and the protection against severe disease included multiple variants of COVID-19, including the B.1.351 variant found in South Africa.

Effectiveness Against COVID-19 Variants

According to information released by Johnson & Johnson, the vaccine was found be 85% effective against severe/critical disease from COVID-19, including that caused by the Delta variant. Data from a clinical study published in The New England Journal of Medicine also supported this finding.

In December 2021, the Centers for Disease Control and Prevention (CDC) endorsed updated recommendations made by the Advisory Committee on Immunization Practices (ACIP), “expressing a clinical preference for individuals to receive an mRNA COVID-19 vaccine over Johnson & Johnson’s COVID-19 vaccine.”

There is currently limited data available showing how effective the vaccine is at protecting against the Omicron variant. One study published in June 2022 found two doses of the vaccine to be 72% effective against hospitalization, 1 to 2 months after receiving the second dose. However, in their request to the FDA to revoke their EUA, Janssen stated they did not intend to update the vaccine to target emerging variants.

When Was it Made Available? 

The Johnson & Johnson vaccine was granted Emergency Use Authorization from the FDA for its single-dose vaccine in February 2021. As of May 2023, Johnson & Johnson (Janssen) supplied 31.5 million doses to the U.S. and more than 19 million people have received the vaccine, according to the CDC.

In August 2020, Johnson & Johnson announced it had a contract with the U.S. government for 100 million doses (the equivalent of $10 per dose) and the option to purchase an additional 200 million doses. In March 2021, President Biden announced plans to purchase an additional 100 million doses, bringing the total to 200 million doses.

However, by January 2023, Johnson & Johnson began to scale back production of its vaccine as demand lowered. Then in May 2023, the vaccine became no longer available in the U.S. after all of the remaining stock of the vaccine expired. Later that month, Janssen requested a voluntary withdrawal of the vaccine's EUA due to low demand and availability of other effective vaccines. The FDA revoked the EUA on June 1, 2023.

Who Can Get the Johnson & Johnson Vaccine?

The Johnson & Johnson vaccine was available for individuals 18 and over. However, in most situations, the CDC recommended the Pfizer, Moderna, or Novavax vaccines over the Johnson & Johnson vaccine.

The FDA limited the authorized use of the Johnson & Johnson vaccine to people for whom other COVID-19 vaccines are not accessible or clinically appropriate, and to those who would otherwise not receive a COVID-19 vaccine.

For those who received the Johnson & Johnson vaccine, the CDC recommends getting an updated dose from Pfizer or Moderna.

Side Effects and Adverse Events

In every clinical trial, participants are asked to record any reactions they have after receiving a medication or vaccine. Adverse reactions are considered to be medication reactions directly caused by a vaccine, whereas a side effect is a physical reaction to a medication.

Initial safety information released for the vaccine shows that the most common reactions after the vaccine was administered included:

• Injection site pain, redness, or swelling
• Fatigue
• Headache
• Muscle aches
• Nausea
• Fever

People who are immunocompromised, including those receiving immunosuppressant therapies, may have a diminished immune response to the vaccine, according to the FDA.

Risk of Guillain-Barré Syndrome

On July 13, 2021, the FDA announced another update to the Johnson & Johnson COVID-19 vaccine label regarding an observed increased risk of Guillain-Barré syndrome (GBS) during the 42 days following vaccination.

GBS is a rare autoimmune disorder of the peripheral nervous system, in which the body's own immune system attacks the peripheral nerves and spinal cord, causing muscle weakness and possible full-body paralysis in severe cases. Most people who develop this disorder recover completely.

Based on data filed with the government's Vaccine Adverse Event Reporting System (VAERS), of the 12 million Johnson & Johnson COVID-19 vaccine doses given in the U.S. at the time, there were about 100 reported cases of people developing GBS. Most cases occurred in men age 50 and older and around two weeks after receiving the vaccination.

Although these findings suggest a link between the vaccine and a small increased risk of GBS, the FDA states it is insufficient to establish a causal relationship. While the FDA and CDC monitored cases of the syndrome, they emphasized that the potential benefits of vaccination continue to outweigh this very low risk.

Risk of Thrombosis With Thrombocytopenia

On May 5, 2022 the FDA limited the authorized use of the Johnson & Johnson COVID-19 vaccine due to a rare, potentially life-threatening risk of thrombosis with thrombocytopenia syndrome (TTS)—blood clots in combination with low levels of blood platelets. The onset of symptoms occurs approximately one to two weeks after administration of the Johnson & Johnson COVID-19 vaccine.

Incidents of TTS following the Johnson & Johnson COVID-19 vaccine were reported in men and women, in individuals 18 years and older; reporting was highest in women ages 30 through 49.

This action followed a previous April 13, 2021, FDA and CDC joint recommendation to temporarily pause administration of the Johnson & Johnson COVID-19 vaccine while the agencies investigated six reported cases of a rare but severe type of blood clot that affects the brain called cerebral venous sinus thrombosis (CVST) occurring along with thrombocytopenia (low platelet count), which can make the condition difficult to treat.

In their initial review the CDC and FDA accounted for nine additional cases of rare blood clots paired with low platelet counts, bringing the total to 15 out of 8 million administered doses. Most cases occurred in women between the ages of 18 to 49 within one to two weeks of vaccination. The agencies concluded that the potential benefits outweigh this very rare risk and lifted the pause after 10 days.

A warning was added to the fact sheets for healthcare providers and vaccine recipients and caregivers about the rare risk of thrombosis in the cerebral venous sinuses and other sites (including blood vessels in the abdomen and veins of the lower extremities) along with low platelet counts after receiving the vaccine.

Healthcare providers were also warned that treating a suspected case of this condition (known as thrombosis with thrombocytopenia) with the blood thinner heparin may be harmful and alternative treatments may be needed along with a consultation with hematology specialists.

Funding and Development

Johnson & Johnson co-funded the development of the vaccine as part of Operation Warp Speed (OWS) with funding from the Biomedical Advanced Research and Development Authority (BARDA), which is a U.S. government program. OWS is a public-private partnership initiated by the U.S. government to facilitate and accelerate the development of a COVID-19 vaccine, manufacturing, and distribution of COVID-19 vaccines. Johnson & Johnson said $1 billion has been invested in the vaccine project by both the company and BARDA.

The U.S. government announced a partnership with Merck to help accelerate the production of the Johnson & Johnson vaccine. Merck was to receive $268.8 million from BARDA to adapt and make available its manufacturing facilities for producing the Johnson & Johnson COVID-19 vaccine.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.