Key Takeaways

The latest results from a Phase 3 clinical trial show Johnson and Johnson’s one-shotcoronavirusvaccine is 66% effective against moderate to severe COVID-19.

The results are reflective of the vaccine’s effectiveness globally, and show levels of protection are different around the world. While the vaccine was 72% effective among participants in the U.S, it was only 57% effective among participants in South Africa, where a highly-transmissible SARS-CoV-2 variant first emerged.

Notably, nobody in the clinical trial needed to be hospitalized for COVID-19, and nobody died of the disease.

Earlier this month, results from Phase 1/2a clinical trials indicated that the company’s vaccine induced immune responses against SARS-CoV-2, the virus that causes COVID-19, in both young and elderly participants.

An Overview of the Johnson & Johnson COVID-19 Vaccine

According to the report, Johnson & Johnson randomly assigned healthy adults between the ages of 18 and 55 and those 65 and older to receive either a high or low dose of the vaccine, or a placebo. A select group of participants in the 18-to-55 cohort received a second dose of the vaccine. In total, the trial included 805 participants.

“Most of the volunteers produced detectable neutralizing antibodies, which researchers believe play an important role in defending cells against the virus, after 28 days, according to the trial data,” said a Johnson & Johnson statement.“By day 57, all volunteers had detectable antibodies, regardless of vaccine dose or age group, and remained stable for at least 71 days in the 18-to-55 age group.”

The company is working with its pharmaceutical arm, Janssen, to develop the vaccine.

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What Is an Immune Response?

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“Your immune system protects you against disease,” says Soma Mandal, MD, a board-certified internist in New Jersey. “When the immune system (composed of various organs) recognizes a particular germ (e.g. bacteria, viruses) as foreign, it launches antibodies that help destroy the germ.”

Mandal says this process is referred to asB-cellimmunity.T- cellimmunity, on the other hand, occurs when “the immune system remembers a particular germ and destroys it before it can make you sick again.”

Vaccines operate similarly, except they are designed to imitate an infection, meaning the immune system remembers and protects without a person becoming ill in order to do so, Mandal says. Of course, minor symptoms may occur as a result of a vaccine.

Johnson & Johnson’s Early Results

In October, Johnson & Johnson announced early results showing that a single dose of their vaccine could induce antibodies in 97% of study participants that effectively neutralized the virus in the laboratory, but the company still required additional information on the effectiveness of the vaccine.

What Does It Take to Make a COVID-19 Vaccine?

Then, they experienced a setback in their trials when a participant experienced an unexplained illness. No specific details were provided about what happened due to patient privacy. Regulators determined on October 23 the event was not related to the vaccine and the trial was safe to resume.

Evaluating Safety

Participants in all three groups (high-dose, low-dose, and placebo) of the clinical trials reported mild symptoms, including:

Adverse reactions were less common in the older age group. In the case of the participants who received the two-dose regimen, fewer reactions occurred after the second dose.

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Five participants experienced more serious symptoms, with one participant visiting the hospital for a fever associated with vaccination—the participant recovered within 12 hours. The remaining four cases were confirmed to be unrelated to the vaccine.

What You Need to Know About the Johnson & Johnson COVID-19 Vaccine Trial Pause

Next Steps

HHS Expands COVID-19 Vaccine Eligibility to People 65 and Older

“We are aiming for 1 billion doses in 2021,” Stoffels said. “If it is a single dose, that means 1 billion people. But it will be in a ramp-up throughout the year…It’s a few weeks too early to be giving final numbers on what we can launch in the first couple months.”

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 ourcoronavirus news page.

7 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Johnson & Johnson. Johnson & Johnson Announces Single-Shot Janssen COVID-19 Vaccine Candidate Met Primary Endpoints in Interim Analysis of its Phase 3 ENSEMBLE Trial.

Sadoff J, Le Gars M, Shukarev G, et al.Interim results of a phase 1–2a trial of ad26. Cov2. S covid-19 vaccine.N Engl J Med. 2021;0(0). doi:10.1056/NEJMoa2034201

Johnson & Johnson.Johnson & Johnson COVID-19 Vaccine Candidate Interim Phase 1/2a Data Published inNew England Journal of Medicine.

Centers for Disease Control and Prevention.Understanding Vaccines.

Johnson & Johnson.Johnson & Johnson Posts Interim Results from Phase 1/2a Clinical Trial of its Janssen COVID-19 Vaccine Candidate.

Janssen.Johnson & Johnson Prepares to Resume Phase 3 Ensemble Trial of Its Janssen COVID-19 Vaccine Candidate in the U.S.

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