J&J's Covid-19 Vaccine: How Does the One-Dose Shot Compare With Others? -- Update
February 27 2021 - 7:47PM
Dow Jones News
By Peter Loftus
Johnson & Johnson's Covid-19 vaccine was authorized for use
in the U.S. by federal health regulators. It is the third shot to
be cleared after shots from Pfizer Inc. and its partner BioNTech SE
and from Moderna Inc. And it is the first shot requiring just one
dose, rather than two. Here's what we know and don't know:
How do the three Covid-19 vaccines compare?
They all work well, health experts say. The Pfizer-BioNTech and
Moderna shots were more than 94% effective in their late-stage
trials, while J&J's effectiveness was 66%. But the difference
may be less than it seems. The Pfizer-BioNTech and Moderna shots
were tested before the emergence of strains like one first
identified in South Africa, which various studies have indicated
eludes vaccines somewhat, though they still work against it.
J&J's vaccine was tested in South Africa, and its effectiveness
wasn't as high there as in other countries, hurting the vaccine's
overall effectiveness. Yet health experts say J&J's vaccine is
plenty effective. Importantly, it was 85% effective against severe
Covid-19 at least 28 days after vaccination. That suggests the
vaccine should help many people avoid the kinds of serious cases
that result in hospitalizations.
Which Covid-19 vaccine should I get?
The first one you can, health authorities say. It is possible
that individuals won't have much of a choice because of limited
supplies and the vaccination site might only offer one of the
shots. If you do have a choice, there are some key differences that
could guide your decision. J&J's vaccine is given as a single
dose, which may be a more convenient option than the two doses
required for both of the Pfizer-BioNTech and Moderna vaccines,
given three or four weeks apart. Only the Pfizer-BioNTech vaccine
is authorized for adolescents 16 and 17 years old, while J&J
and Moderna's shots are cleared for those 18 and older.
When can I get J&J's shot?
J&J has been making doses while testing its shot, so it will
be able to ship nearly four million doses within a few days.
Vaccinations will be limited at first, however. The company plans
to deliver 20 million doses for U.S. use by the end of March. Then
production will really pick up, as J&J projects shipping 100
million doses by the end of June.
How effective is J&J's Covid-19 vaccine?
It appears to work well. The vaccine's 66% effectiveness rate
shows it can protect most vaccinated adults from moderate to severe
Covid-19, the disease caused by the coronavirus. And the vaccine
was even more effective preventing severe disease specifically,
posting the 85% rate. By comparison, an annual flu shot is
considered to work well if it is 60% effective.
What are the side effects of J&J's vaccine?
The most common side effects among people who received the
vaccine were injection-site pain, headache and fatigue. Most were
mild to moderate. J&J has received preliminary reports of two
cases of severe allergic reactions in vaccine recipients, one of
which was anaphylaxis.
How was J&J's Covid-19 vaccine tested?
Starting in September, J&J enrolled more than 44,000 adults
in the U.S. and several other countries including Brazil and South
Africa in a clinical trial. The subjects received a single dose of
either the vaccine or a placebo. Researchers counted how many
people subsequently contracted moderate to severe Covid-19 starting
14 days after vaccination, until a certain number of people fell
ill. Researchers then examined whether there were fewer vaccinated
people than unvaccinated people among the Covid-19 cases.
Researchers also monitored for side effects among the study
subjects.
How does J&J's vaccine work?
The vaccine uses a harmless type of virus, called an adenovirus,
which can cause cold symptoms. It is modified to contain the DNA of
the so-called spike protein found on the surface of the new
coronavirus. After injection, the cold-virus vector carries the DNA
payload into human cells. Once inside the cells, the DNA payload
causes the production of the spike protein. This, in turn, triggers
an immune response that can later defend against the real
coronavirus if a vaccinated person is exposed to it.
What don't we know about J&J's Covid-19 vaccine?
We don't know its safety and effectiveness in children, or among
pregnant women, their fetuses or women nursing babies. We also
don't know how long vaccine-induced protection will last. The
company is conducting a separate study testing whether adding a
second dose improves its performance. Also uncertain is whether the
vaccine can help curb the spread of the virus by infected people
who don't have symptoms, a group that turns out to be responsible
for a lot of transmission. A preliminary analysis by J&J gave
tantalizing signs the company's vaccine could limit asymptomatic
spread, by reducing infections that didn't cause symptoms in study
subjects.
Does J&J's vaccine protect against new coronavirus
strains?
The vaccine was less effective in South Africa and Latin America
than in the U.S. That could be a sign the vaccine is less
protective against strains circulating in those regions, though
J&J is still conducting that analysis. J&J's vaccine was
57% effective in South Africa and 66% in Latin America, compared
with 72% in the U.S. during the late-stage trial, according to
J&J. Even at the lower levels of effectiveness in South Africa
and Latin America, health experts say, J&J's vaccine works
well. The company said it is working on a version of the vaccine
targeting the variant first identified in South Africa. Even in
study subjects there, the shot still performed above what health
experts say is needed to protect many people and provide the
community immunity needed to move to a post-pandemic life.
Write to Peter Loftus at peter.loftus@wsj.com
(END) Dow Jones Newswires
February 27, 2021 19:32 ET (00:32 GMT)
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