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Now that a Pfizer booster dose has been approved for Americans 65 years of age and older, people with underlying health conditions, and people working in high-risk environments, many people are asking: can I mix and match vaccines?

“Things change so quickly when it comes to science, epidemiology, virus, people’s behavior – it’s hard to keep up,” said Dr Kami Kim, director of infectious diseases and international medicine at the ‘University of South Florida Morsani College of Medicine.

This means that what experts know about mixing and pairing doses is changing, but here’s what you need to know now:

Official recommendations say to avoid mixing and pairing.

According to official guidelines from the Centers for Disease Control and Prevention, when possible, people who have received the Pfizer vaccine should receive two doses of this vaccine as well as a booster dose if they are eligible.

Likewise, people who receive Moderna vaccine should receive two doses from this manufacturer. Federal regulators have yet to weigh a booster dose for Moderna, but they have approved a third dose of the vaccine for people with weakened immune systems.

And the folks at Johnson & Johnson should stick to one dose of their vaccine – for now.

“This is an area of ​​active research, and there are no specific guidelines for it,” said Dr. Angela Branche, an infectious disease expert at the University of Rochester School of Medicine.

But experts now say it’s OK to mix mRNA vaccines under certain circumstances.

Last winter, the CDC changed its official position on vaccine mixing and pairing somewhat, from a “never do” approach to new guidelines that say it’s okay to mix and match. match the two mRNA vaccines (Pfizer and Moderna) under “exceptional circumstances.” As if someone didn’t know what they got for their first dose. Or if a second dose of the same vaccine is not available for some reason.

When the CDC agreed to a third dose of the two mRNA vaccines for people with weakened immune systems in August, they also left the door open to mixing and pairing. “If the mRNA vaccine product administered for the first two doses is not available or is unknown, either COVID-19 mRNA vaccine product can be administered,” the agency said.

Johnson & Johnson is a question mark in all of this.

Almost 15 million people in the United States have received the Johnson & Johnson single-dose vaccine, which uses a different mechanism to produce antibodies than the two mRNA vaccines. And many feel like they’ve been left behind in conversations about boosters and mixing and pairing.

The CDC says people who have been given a dose of Pfizer or Moderna, but are unable to get a second dose, may get a Johnson & Johnson vaccine – and they are considered to be fully vaccinated with that vaccine after two weeks. The previous move basically doesn’t count.

Johnson & Johnson recently published results suggesting that a second booster dose of their vaccine produces a strong immune response. It indicates that two doses were 94% effective in protecting against symptomatic infections, compared to a single dose of approximately 72% effective against moderate to severe illness in the United States.

But people who have received the Johnson & Johnson vaccine are not eligible for boosters at this point. Neither are immunocompromised people who received the Johnson & Johnson vaccine.

Some experts believe we are moving towards vaccine mixing and pairing.

Some countries in Europe – which have approved vaccines different from those here in the United States – have recommended a mixed-dose approach during the pandemic. And experts like Kim have said we might just be heading this way here in the United States.

“There are studies where people look at all of this. They are looking at all kinds of different combinations, ”Kim said.

“It looks like mixing and pairing is safe. So what a lot of people have done – and informally advise people – is that it shouldn’t hurt you to go for another dose, ”she added, claiming that it doesn’t. really only concerns people at high risk of serious consequences, and this is not a formal policy. Everyone should ideally sit tight.

Also, it is very important to remember that vaccines work well and keep people away from the hospital. Also, keep in mind that the United States has plenty of booster shots and enough for children, if and when they are approved. There’s no need to feel like you can’t get the same shot.

“I understand people’s anxiety and worry and I really want to know what to do to be as safe as possible and to be protected,” Branche said. “But you know the first rule of medicine is not to give people what they don’t need.”

Experts are still learning about COVID-19. The information in this story is what was known or available at the time of publication, but directions may change as scientists find out more about the virus. Please consult the Centers for Disease Control and Prevention for the most recent recommendations.


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