Janssen (Johnson & Johnson) COVID-19 vaccine Phase 3 trials

Nearly 80,000 doses of the one-shot Johnson & Johnson vaccine are expected at mass vaccination sites around Illinois early this month, such as the one in Chicago at United Center, where thousands of seniors have booked appointments.

Dr. Habibul Ahsan, who ran trials for the J&J vaccine at the Institute for Population and Precision Health at the University of Chicago, stressed that the vaccine is safe, well-tolerated and more or less wiped out hospitalizations and deaths among the 44,000 people who participated in the trial that preceded its FDA clearance.

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Habibul Ahsan, director of the Institute for Population and Precision Health at the University of Chicago

Vaccines work against infectious diseases by exposing the body to some elements of the infectious agent — in this case, the coronavirus — in a format such that the agent does not cause people harm but still causes an immune response. If the coronavirus comes into contact with the body in the future, it would then fight off the infection.

COVID-19 vaccines work by preventing the coronavirus' spike protein from attaching onto cells and infecting tissues. But instead of the mRNA vaccines manufactured by Moderna and Pfizer-BioNTech, which harmlessly expose the body and immune system to an element of the coronavirus' genetic code, the J&J vaccine is a "viral vector" vaccine, using a reasonably harmless adenovirus (which causes a common cold) that has been engineered to carry the code for the coronavirus' spike protein.

"Once you insert it into your muscle cell, it does exactly what it's supposed to do like any other vaccine," Ahsan said. "It exposes the body, so the body sees some foreign element. It develops immunity and antibody cells, all of those. In the future, when the real virus comes, those can fight the real coronavirus."

J&J has used viral vector vaccines before against diseases like Zika virus — because the technology already existed, researchers could quickly adapt it to the coronavirus last year — and Ahsan said more than 100,000 people have already been vaccinated against COVID-19 with the vaccine.

While the Moderna and Pfizer vaccines, when submitting data for approval from the FDA, showed efficacy rates of around 95% each, the J&J vaccine was shown to be 72% protective in the United States. But Ahsan said immunity is more complicated than that.

There is immediate immunity: the body recognizes that something it does not recognize has been injected into it, and the immune system fights against it. After that, the immune system begins making antibodies, the proteins that neutralize viruses and other pathogens. Weeks later, the body programs the rest of its immune cells to further recognize pathogens like the coronavirus.

"When you inject vaccine, it takes one to two weeks," Ahsan said. "In other words, you will have enough immune cells to be able to fight the virus when you subsequently get exposed to it. That's why it takes some time before you actually develop protection for any vaccines. This vaccine, for Johnson & Johnson, you see some level of protection from 14 days after the first vaccination, and it starts becoming stronger and stronger."

After 28 days, the protection is stronger still: 85% against severe disease in all the regions around the world in which it was studied.

"When it says '72% effective,' what it means is that still individuals may develop a mild type of COVID, which would be less than what they'd get with the Pfizer and Moderna," he said. 

Though the J&J vaccine may offer less protection against mild symptomatic COVID-19, Ahsan said it is as protective if not more protective than the other two vaccines. The Pfizer and Moderna were only tested against the original coronavirus strain; the J&J one was tested against more contagious strains. But even in South Africa, no one who had gotten the J&J vaccine went to the hospital or died.

At this point, Anthony Fauci, the president's Chief Medical Advisor and the nation's top infectious diseases expert, has urged Americans to take the first vaccine available to them. In the future, Ahsan said people might exercise choice about when they want their immunity to kick in, or whether they can budget two trips to get shots instead of one.

"Right now, those luxuries are really not helpful from a public health perspective in terms of controlling the pandemic," he said.


Transmission electron microscopic image of an isolate from the first U.S. case of COVID-19, formerly known as 2019-nCoV. The spherical viral particles, colorized blue, contain cross-section through the viral genome, seen as black dots.

As of March 4, Chicago's COVID-19 positivity rate is 2.9%, lower than it had ever been over the summertime, between the two surges.

Five percent is the city's target positivity. A citywide positivity of less than 2% is one of the metrics — alongside fewer than 20 diagnosed COVID-19 cases in Chicago per day, fewer than 20 emergency room visits for COVID-like illnesses and fewer than 20 intensive care unit beds occupied by COVID-19 patients — that the city would need to reach with week-to-week stability to show controlled transmission of the coronavirus.

The city's seven-day rolling average of daily cases was 287, indicating moderate risk (200-399 cases) according to the Chicago Department of Public Health but up 8% from the week before. 

As of Feb 21-27, COVID-19 percent-positivities remain below 5% in all four mid-South Side lakefront ZIP codes.

  • In 60653, covering North Kenwood and Bronzeville, there were 18 confirmed cases of COVID-19, compared to 19 from Feb. 14-20, and no deaths, down from one the week before. There was a 1.8% positivity rate out of 999 tests performed, down from 2.2% from the week before. The number of tests performed rose 17%.
  • In 60615, covering northern Hyde Park, southern Kenwood and northern Washington Park, there were 19 confirmed cases, up from 20 the week before, and one death, same as the week before. There was a 0.8% positivity rate out of 2,295 tests, down from 1.1% the week before. The number of tests performed rose 22%.
  • In 60637, covering southern Hyde Park, southern Washington Park and Woodlawn, there were 24 confirmed cases, up from 17 the week before, and no deaths, down from one the week before. There was a 0.6% positivity rate out of 3,996 tests, up from 0.4% the week before. The number of tests performed rose 4%.
  • In 60649, South Shore, there were 23 confirmed cases, up from 14 the week before, and no deaths, the same as the week before. There was a 2.2% positivity out of 1,042 tests, up from 1.2% the week before. The number of tests performed dropped 10%.

The city’s figures are accurate as of March 4, recorded at and change as additional past data comes in.

From Feb. 20-26, the University of Chicago reported no positive cases out of 3,476 tests; the week before, the school identified one positive case out of 5,552 tests. All test results are reported to the city.

Since Sept. 18, there have been 793 total coronavirus cases at the U. of C.

As of March 4, there are 33 cases with COVID-19 at the U. of C. Medical Center. On Feb. 22, there were 27; on Feb. 4, there were 41. At the height of the second surge, in November, there were around 110; at the height of the first surge, in April, there were 140.

The city's website for free COVID-19 testing is; more information is available at

Testing is available on the mid-South Side at:

The city's website for vaccine information is The city's online platform for vaccine scheduling is, where bookings for seniors to get vaccines at the United Center are available.

Patient registration for the COVID-19 vaccine at the UCMC is not available at this time; vaccines are being offered to eligible patients through a lottery, with patients being notified when it is their turn to schedule an appointment.

Howard Brown is offering the COVID-19 vaccine to essential frontline workers and those aged 65 and older, with sign-up at 872-269-3600.

The Cook County government is offering sign-up for vaccines at

Vaccine signup is also available online through Walgreens and Walmart.

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