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results confirm what health officials and scientists have known for
some time based on earlier research. But the study is important because
vaccine effectiveness data on the mix-and-match booster strategies in
the real world has been limited.The new data, from a 10-state
study conducted by independent researchers, may provide clarity amid a
confusing stew of data about the single-dose vaccine.
It shows that
three doses of a messenger RNA vaccine perform the best, while a Johnson
& Johnson vaccine followed by a messenger RNA booster shot is next
best. Two shots of Johnson & Johnson provide a lower level of
protection, with a single shot just 31% effective against
hospitalization.
"That's too low, especially in this world where
we have access to other things," said Natalie E. Dean, a biostatistician
at Emory University's Rollins School of Public Health. "One priority is
making sure that people who only received one dose [of Johnson &
Johnson vaccine] are aware that they should go and get, preferably, a
messenger RNA vaccine."
The
data also suggest a second boost with a messenger RNA vaccine may need
to be considered, even for individuals who have received two doses of
Johnson & Johnson, said Boghuma Titanji, an infectious-diseases
expert at Emory University. "This is not yet a formal recommendation,"
Titanji said, "but is something individuals who fall in this category
should discuss with their health-care provider."
The takeaway: "If
you can get the messenger RNA vaccine series, and especially get one as
a booster, this [study] confirms that is the way to go," said Jeanne
Marrazzo, director of the Division of Infectious Diseases at the
University of Alabama at Birmingham.
Experts said the latest CDC study underscores what some experts say is a critical need for clearer recommendations on boosters.
Last
fall, the CDC gave Americans eligible for boosters the choice of any
one of the three vaccines, regardless of their original shot. In
December, however, the agency updated its guidance to recommend people
get the messenger RNA vaccines over Johnson & Johnson because of
concerns over the an extremely rare but potentially fatal blood clot
issue.
"Right now, there aren't recommendations for people who got
two doses of J & J to get a third messenger RNA shot," said William
Moss, executive director of the International Vaccine Access Center at
the Johns Hopkins Bloomberg School of Public Health. (Those who are
moderately to severely immunocompromised are already recommended to get a
third dose.) "The messenger RNA vaccines seem to be providing more
protection . . . What I'd like to see is a very simple recommendation:
that everyone get three doses, and they should be messenger RNA
vaccines."
Several studies have shown the Pfizer and Moderna
vaccines remain highly effective at preventing the worst outcomes from
infections even as protection against less severe illness waned over
time.
Although the Johnson & Johnson vaccine provides a lower
level of initial protection than the messenger RNA vaccines, the company
has pointed to evidence that its vaccine's protection may not erode as
quickly.
A study funded by the division of Johnson & Johnson
that developed the vaccine and published in JAMA Network Open found that
vaccine effectiveness was stable over six months - 81% effective at
preventing hospitalization, though it measured a period before the
omicron variant's emergence.
"If there's something we've learned
in the pandemic - and it's not a new lesson - the most informative
papers come from people who are independent of the study," said John P.
Moore, a professor of microbiology and immunology at Weill Cornell
Medicine.
Moss said it's important for the public to keep in mind
that the goal of vaccination is to prevent severe disease and death. But
public messaging became muddled, he said, in part because early studies
showed the messenger RNA vaccines provided protection against
infection, raising "false expectations."
It's natural for the
levels of virus-fighting antibodies in the blood to wane over time, Moss
added. That's part of the design of the body's immune response.
"Otherwise our blood would be chock full of antibodies and [blood]
wouldn't be able to flow . . . and deliver oxygen to the cells," he
said.
The CDC study analyzed data from more than 80,000 emergency
room or urgent care visits, and more than 25,000 hospitalizations among
adults with covid-19-like illness in 10 states, from mid-December to
March 7, a period which includes the omicron variant surge.
When
researchers compared the effectiveness of several vaccine combinations
in preventing emergency room or urgent care visits, they found:
- A single Johnson & Johnson shot offered 24% effectiveness;
- Two Johnson & Johnson shots offered 54% effectiveness;
- A combination of Johnson & Johnson with one messenger RNA booster offered 79% effectiveness;
- Three messenger RNA shots offered 83% effectiveness.
Protection
against hospitalization, meanwhile, was significantly higher with three
doses of the messenger RNA vaccines, which offered 90% effectiveness.
That compared with:
- A single Johnson & Johnson shot, which offered 31% effectiveness;
- Two Johnson & Johnson shots, which offered 67% effectiveness;
- A Johnson & Johnson shot with a messenger RNA booster, which offered 78% effectiveness.
When
the Food and Drug Administration authorized Johnson & Johnson's
vaccine in February 2021 for all adults, many believed the one-and-done
approach would make it a tool to vaccinate the world. But last spring,
federal officials halted the use of the vaccine for 10 days, while they
looked into reports of six cases of an extremely rare but potentially
life-threatening type of blood clot among the millions of people who had
received the shots in the United States. The vaccine's use waned
thereafter, due to supply problems, as well as concerns over the
clotting issue.
Nine deaths - among seven women and two men - have
been confirmed in connection with the blood clot issue through
September. Seven of those patients, who ranged in age from 28 to 62, had
underlying medical conditions, including obesity, hypertension and
diabetes.
The Washington Post's Carolyn Y. Johnson contributed to this report.
