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On Sept. 23, 2020, U.S. pharmaceutical and medical devices company Johnson & Johnson, Inc. announced the start of the Phase 3 human clinical trial for its experimental Ad26.COV2.S vaccine for COVID-19. The New Jersey-based company, which is partnering with its subsidiary Janssen Pharmaceutica NV of Belgium on development of the vaccine, is planning to enroll 60,000 volunteers to participate in the trial.

Johnson & Johnson recently announced the results of the Phase 1/2a clinical trial for the Ad26.COV2.S vaccine. The double-blind, randomized, placebo-controlled trial included 796 participants divided into two groups consisting of 402 healthy adults 18 to 55 years of age in one group and 394 healthy elderly individuals 65 years of age and older in the other. The first group was broken out into cohort 1a and cohort 1b. The second group was cohort 3.

Each of the participants were given a single entramuscular injection of Ad26.COV2.S at dose levels of either 5×1010 or 1×1011 viral particles (vp) per dose of vaccine. After four weeks of observation, 99 percent of all the participants developed antibodies to the SARS-CoV-2 virus.

More Than Half of Trial Participants Develop Adverse Events After Getting Ad26.COV2.S

About 58 percent of participants in cohorts 1a and 1b experienced local adverse events, while 64 percent of them also suffered systemic adverse events. Of the participants in cohort 3, 27 percent of them experienced local adverse events, while 36 percent suffered systemic events. Of the healthy adults aged 18 to 55 years old in cohorts 1a and 1b, 19 percent of them came down with fevers, while four percent of the adults aged over 65 years old in cohort 3 developed fevers.

Most of the fevers were considered mild or moderate and resolved within one to two days after vaccination. However, five percent (20) of the participants in cohorts 1a and 1b suffered from Grade 3 fevers of over 101.3°F. Grade 3 adverse events are considered to be serious reactions. They are only one grade removed from "life-threatening" (Grade 4) and just two grades from "death" (Grade 5).

According to a news report on Johnson & Johnson's Phase 1/2a trial:
"[T]here were two severe adverse events recorded. One participant had hypotension; however, this effect is not related to vaccination as the participant had a history of hypotension. Another participant with fever was hospitalized as a suspected case of COVID-19; however, the fever resolved within 12 hours."
The most common adverse events experienced by trial participants were pain the injection site, fatigue, headaches and myalgia (muscle pain).

Ad26.COV2.S Uses AdVac Technology to Carry SARS-CoV-2 Genetic Code into Cells

On Mar. 20, Johnson& Johnson announced it had been given $1B by the U.S. Biomedical Advanced Research and Development Authority (BARDA) in the Department of Health and Human Services (HHS) to develop an advenovirus vectored COVID-19 vaccine using J&J's AdVac technology and PER.C6, a cell line derived by transformation of embryonic retinal epithelial cells with human adenovirus type5 E1 region gene, for production.

J&J's Ad26.COV2.S vaccine combines the genetic material from the SARS-CoV-2 virus that causes COVID-19 with an adenovirus that causes the common cold but has reportedly been genetically modified so that it can no longer replicate and cause disease. The "disarmed" adenovirus acts as a vector, carrying the SARS-CoV-2 virus's genetic code into human cells and is supposed to teach the immune system to create antibodies to attack the SARS-CoV-2's "spike proteins" that enable the virus to infect cells.

This recombinant adenovirus technology, known as AdVac, was used to produce Johnson & Johnson's Ebola vaccine, which was approved by the European Commission (EC) on July 1, 2020. J&J officials have stated the first batches of a COVID-19 vaccine could be available for emergency use authorization in early 2021.

Ad26.COV2.S, BARDA, Biomedical Advanced Research and Development Authority, COVID-19, Department of Health and Human Services, HHS, J&J, Janssen Pharmaceutica, Johnson & Johnson, Marco Cáceres, National Vaccine Information Center, NVIC, SARS-CoV-2, The Vaccine Reaction