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Johnson & Johnson Krem do Twarzy - Odkryj Tajemnice Zdrowej i Promiennej Skóry
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Dr. Leana Wen, an emergency physician and professor at George Washington University, says that's a big plus for the J&J vaccine.
"If there are individuals who may not like needles, who may have concerns about returning for a second shot, who may not want the inconvenience of scheduling a second appointment, or who may be concerned that there isn't enough supply of the vaccine at the moment for a second shot — for those individuals, that convenience of being done [after one dose], fully vaccinated, is really important," Wen says.
Still, the J&J vaccine is a little different from the others. Here's what you need to know.
How does the Johnson & Johnson vaccine work?
How effective is the Johnson & Johnson vaccine?
When companies report results from clinical trials, they report the "percent effectiveness" of a vaccine. A vaccine that's 90 percent effective at preventing illness doesn't mean 10 percent of people who received it will get sick, rather, it means people who got the shot were 90 percent less likely to get sick, compared with people who received a placebo.
In Johnson & Johnson's trial, researchers looked at different outcomes in different parts of the world. In the United States, for example, the vaccine was found to be 72 percent effective at preventing what the company defined as moderate to severe Covid-19. That was a broad definition, which ranged from a combination of milder symptoms, such as fever and headache, to more severe symptoms, such as shortness of breath and low oxygen levels.
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And it prevented 100 percent of hospitalizations and deaths related to Covid-19. No one who got the Johnson & Johnson shot was hospitalized or died of Covid-19 during the study's follow-up period of 28 days after vaccination.
What's more, the Johnson & Johnson vaccine's effectiveness against severe disease was found to increase over time — to more than 90 percent within a month and a half after vaccination.
What all that means in practice is that even if a vaccinated person is infected with the coronavirus, the illness is likely to be one that can be managed at home, experts say. That's true regardless of the variant.
"Even if they get Covid, their symptoms are much more mild than people who got the placebo and got Covid," said the director of the Alabama Vaccine Research Clinic, Dr. Paul Goepfert, a professor of medicine at the University of Alabama at Birmingham. Goepfert was an investigator in the Johnson & Johnson vaccine trials.
How does the Johnson & Johnson vaccine compare to other vaccines?
At first glance, the Johnson & Johnson vaccine looks to be the inferior option compared to the vaccines from Pfizer-BioNTech and Moderna, both of which reported around 95 percent effectiveness in their Phase 3 clinical trials.
Experts say that in no way should those percentages be interpreted in a way that suggests that the Johnson & Johnson shot — with its 72 percent effectiveness — is 23 percentage points less effective.
The percentages can't be compared directly to one another, because the trials were run differently. The vaccines were studied at different times during the pandemic, when different variants were circulating.
SARS-CoV-2, the virus that causes Covid-19, has been changing ever since it was discovered in Wuhan, China.
"The virus that swept through China was not the virus that left China," Offit said. "The virus that left China was the first variant, and it was more contagious than the one that originally popped up."
That could account for the decreased effectiveness reported in Johnson & Johnson's trials — there's no way to know how the Moderna and the Pfizer-BioNTech vaccines would have fared in the same scenario.
"I am speculating," said Dr. William Schaffner, an infectious diseases expert at Vanderbilt University Medical Center, "but the notion is that, yes, we think that if the Moderna and Pfizer people had been in South Africa at the same time that Johnson & Johnson were testing their vaccine, we would probably get all very comparable results."
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.
