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Implementing a mixed covid-19 booster vaccine policy would provide two clear benefits: a stronger immune response to the extra dose and much less confusion for people seeking booster doses.
The first results of research by a team led by the US National Institutes of Health (NIH) show that the administration of a different booster vaccine than the one originally received provides an immune response stronger than the administration of an additional dose of the same vaccine, results that coincide with the investigation carried out at the beginning of the year in the United Kingdom.
Booster shots may soon be recommended for people over 40, source says
Vaccine experts are not surprised that mixing vaccine types is safe.
People do this regularly with a variety of vaccines, including flu vaccines, which are made by six or seven different companies in the United States alone in a given year, using a variety of formulas.
These include vaccines made from chicken eggs, caterpillar cells, and dog kidney cells, vaccines that protect against three or four different strains of flu, and vaccines that are given by injection or nasal spray.
In many countries, children receive polio vaccines as a shot first and then they are boosted with a different oral formulation, a combination that is safer and more effective.
Both Pfizer's and Moderna's covid-19 vaccines are mRNA vaccines, made from a genetic material called lipid-wrapped messenger RNA that instruct the body's cells to produce tiny pieces of coronavirus that stimulate an immune response.
Johnson & Johnson's Janssen vaccine uses a different method: a genetically modified common cold virus, called adenovirus, which cannot replicate itself, but can deliver a small piece of coronavirus to cells and also stimulate a response. immunological.
AstraZeneca's covid-19 vaccine uses technology similar to Johnson & Johnson's, and several studies have shown that alternating doses of this vaccine with that of Pfizer generates a strong immune response.
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What is known about the covid-19 vaccine mix for the booster dose?
Broader immune responses
Mixing different types of vaccines could amplify the type of immune response, said Dr. Angela Branche, an associate professor at the University of Rochester School of Medicine who is helping lead some of the clinical trials that mix booster doses.
A vector vaccine, like the one from Janssen or AstraZeneca, stimulates strong cellular immunity, he said.
MRNA vaccines stimulate powerful waves of antibodies.
The mixture of the two, he said, "can broaden the depth of the immune response."
"I think the data will show that the use of reinforcements is certainly very effective in providing additional and longer protection," he told CNN.
"We can reinforce with all vaccines."
Last week, Dr. Kirsten Lyke, a professor of Medicine at the University of Maryland, presented the NIH team's findings to the US Food and Drug Administration (FDA) vaccine advisers. in English).
The FDA asked them to comment on the issue of mixed boosters and is preparing an emergency use authorization proposal for boosters that could incorporate their ideas.
Questions from the audience about the coronavirus: Is the effectiveness of vaccines lost if you contract covid-19?
Although Lyke stressed that the data is not yet complete, he said it showed that booster with a different type of vaccine than the original dose provided a stronger antibody response than booster with the same type.
"What I want to point out is that the neutralizing antibodies increased in response to any booster in the primary vaccination series," he told the FDA's Vaccines and Related Biologics Advisory Committee (VRBPAC).
"The study was not designed to compare between reinforcements," he added, in other words, it was not designed to tell people which particular brand might be better.
But that might not matter, because the other advantage of allowing people to boost themselves with any of the three vaccines licensed in the US would be flexibility.
Confusing messages about booster shots
Right now, the authorization of the reinforcements is somewhat complicated.
Pfizer has an emergency use authorization for a booster vaccine for those who received the first two doses at least six months ago and are 65 years of age or older, or who are 18 years of age or older and are also at risk for a serious illness due to an underlying illness or because their living or working conditions endanger them.
Moderna and Johnson & Johnson also requested authorization for the reinforcements.
Moderna's request is nearly identical to Pfizer's, but Johnson & Johnson is asking for boosters for all people 18 and older who have received their vaccine.
If the FDA grants these requests, the VRBPAC members said people will be confused.
"Now the ability to mix, match, and make different groups eligible has been created," said Dr. Jeannette Lee, professor of biostatistics at the University of Arkansas, at last Friday's meeting.
"This is going to be very, very messy in terms of communication."
Johnson & Johnson Asks FDA To Authorize Covid-19 Vaccine Boosters
Dr. Amanda Cohn, an official with the US Centers for Disease Control and Prevention (CDC), who sits on both the VRBPAC and the CDC's Vaccine Advisory Committee, He said it would be very helpful if there was flexibility for people trying to apply boosters, for example for drug providers who go to nursing homes with only one brand of vaccine.
Plus, there's the problem of people who forgot which vaccine they got or lost their records, said Dr. Melinda Wharton, CDC's associate director for Vaccine Policy.
What can happen now?
Dr. Peter Marks, who heads the FDA's vaccine arm, the Center for Biological Research and Evaluation, dropped some hints about the direction the agency might take.
"I think we got what we needed from this debate," he said.
"There seems to be some consensus that this is an important option for people," he added.
"Some believe that it is sufficient data."
He noted that several members of the VRBPAC said they would feel comfortable allowing anyone over the age of 40 to receive reinforcements.
The risk of complications from an inflammatory heart condition called myocarditis drops sharply after age 40, he said.
More booster vaccines against covid-19 are coming.
But not everyone will need it, experts say
This points to the possibility that the FDA will authorize the use of boosters that cover all three vaccines.
CDC's vaccine advisers, the Advisory Committee on Immunization Practices (ACIP), will meet this Thursday to offer guidance on administering boosters.
The ACIP and CDC could lower the FDA parameters in its final decision on boosters, but they do not have the authority to expand them.
covid-19 vaccine