Health

What you need to know about the fourth dose of COVID-19 vaccine


Most people 12 years of age and older are considered “update“With their COVID-19 vaccine if they receive three doses of the mRNA injection from Pfizer-BioNTech or Moderna, or two doses of Johnson & Johnson’s Janssen vaccine. But some public health experts say another dose may be needed in the coming months.

On March 15th, Pfizer and BioNTech Authorization request from the U.S. Food and Drug Administration (FDA) for the fourth dose of their vaccine in people 65 years of age and older. Over the past few days, Albert Bourla, CEO of Pfizer, has said that he believes people will one day need a fourth dose to help prevent infection (a move that will have clear benefits. for corporate profits).
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To authorize a fourth shot, the FDA will look for worrisome signs that vaccine-provided immunity is starting to wane, which could make people more susceptible to adverse effects. more severe effects of COVID-19. Recently data published by the US Centers for Disease Control and Prevention (CDC) showed that protection against hospitalization for COVID-19 waned even after a booster dose of Pfizer-BioNTech or Moderna vaccine. Between August 2021 and January 2022 — a time period that includes episodes of both the Delta and Omicron variants — the booster was 91% effective at protecting from hospitalization for the first two months after people received it, but dropped to 78% in four months after the shot, the shot. The effectiveness of emergency room vaccines and urgent visits for COVID-19 symptoms also decreased, from 87% up to two months after booster shot to 66% four to five months after vaccination. repeat.

Dr Anthony Fauci said: “We don’t know when you reach six months, seven months or eight months after the third dose, whether that 78% will drop to 60%, 50% or 40%. White House chief medical adviser on COVID-19 and director of the National Institute of Allergy and Infectious Diseases. “For that reason, you would be seriously considering a fourth booster for the elderly and those with certain underlying health conditions. What we might see in the reasonable future is that individuals, based solely on age, and perhaps some unidentified underlying health condition, will get an immediate boost. “

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CDC has suggestion fourth dose of mRNA vaccine for people with weakened immune systems, including transplant patients and those undergoing cancer chemotherapy, and other countries have similar guidelines. Israeli health officials have gone a step further; On January 22, as cases and hospitalizations increased, the country authorized the fourth dose of the Pfizer-BioNTech mRNA vaccine for healthcare workers and those over 60 years of age. The decision is based on initial data from the Israeli Ministry of Health and researchers at several Israeli universities showing that of the nearly one million vaccinated people over the age of 60, the fourth dose of the vaccine provided twice as much protection from infection and up to three times as protection against severe illness, compared with those given three doses.

There is growing evidence that all kinds of vaccine-induced protection continue to wane. Scientists have known for a long time that the antibodies humans make immediately after vaccination are relatively short-lived, but vaccines trigger the body to produce immune defenses. Others, including T cells, tend to be more stable. However, even those responses begin to fade after a few months, said Dr. Otto Yang, professor of medicine, infectious diseases, microbiology, immunology and molecular genetics at the University of California, Los Angeles said. That means existing vaccine regimens may need to be supplemented with another booster dose to keep both antibody and T-cell counts high enough to protect people from severe illness, he said. .

But whether people need an extra dose of vaccine, and whether we can anticipate getting vaccinated every year or every few years, depends on what we want the vaccine to be. achieve. Vaccines are not designed to prevent people from getting the virus, but to protect them from getting very sick with COVID-19 and keep them from needing hospitalization and intensive care. Paul Offit, director of the Center for Vaccine Education and professor of pediatrics at Children’s Hospital of Philadelphia, says it’s helpful to keep that goal in mind when thinking about whether a fourth dose is necessary for most people or not.

“We got suspended when we used the word ‘overate’ in describing mild disease,” he said, referring to any infection that occurs in vaccinated and booster populations (most are mild or even asymptomatic). “But it’s a win – it means the vaccine worked for you and protected you from serious illness. We’ve developed a zero-tolerance strategy that we’re going to have to overcome: the idea that it’s impossible to get a mild illness after you’ve been vaccinated. “

If the goal of the COVID-19 vaccine is to protect people from severe illness, Offit says there isn’t enough data to support the need for a booster shot for most healthy adults. “I think we have to accept the view that this is a three-dose vaccine in certain groups and a two-dose vaccine in others,” Offit said.

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Offit, who serves on the FDA’s vaccine advisory committee of independent experts who review the data and make recommendations to the FDA about whether vaccines are safe and effective, said that trying to preserve Protecting the world’s population from mild illness by continuously increasing doses is not a realistic or practical public health goal. The question becomes one of balancing any marginal benefit in protection against mild disease from potential side effects, which for mRNA vaccines include the risk of heart tissue inflammation. “Everything has a cost, including promotion,” he said. “If it doesn’t benefit you in terms of protection against critical illness, then you have to consider the side effects.”

Fauci said health officials will closely monitor the hospitalization rates of those vaccinated and immunized in the coming weeks and months; if it climbs upwards, then it signals a decline in protection even against severe disease, which may warrant another boost. “We don’t know if we need it right now, but as long as this virus is around, I wouldn’t be surprised if we need another shot,” he said.

Nor do he and others predict continued gains as new variations emerge. Up until this point, that strategy was driven by the urgent need to kill the virus as quickly as possible in as many people as possible. But it’s not a long-term or practical game plan. “We’ve been chasing our tails with every variation, and we’ll be forever behind [the virus],” said Dr. Kirsten Lyke, professor of medicine at the University of Maryland, who leads studies on mixing and matching different COVID-19 vaccines.

But now that the majority of the US population has acquired some degree of immunity through infection, vaccination, or both, the National Institutes of Health is launching new studies looking for an approach. more targeted approach to potential booster shots. Instead of reacting to new variants as they emerge and hoping that existing vaccines continue to protect against serious diseases, the scientists there are mapping the mutations of SARS-CoV. -2 and try to engineer vaccines against a range of changes that would ideally quell a number of different diseases, but related strains the virus could produce in the future. The study will involve 1,500 people at 25 sites. “By mid-summer, we’d like to put all the data together so we can make a more scientific assessment of whether the additional boosters are working, if we can,” Lyke said. need them and which ones we might need to use.

Whether a fourth dose is recommended for most Americans depends on future hospitalization rates for those vaccinated and boosters; if they continue to rise, that could prompt health officials to consider recommending another booster dose. In the meantime, Fauci said scientists at the National Institute of Allergy and Infectious Diseases’ Vaccine Research Center are investigating whether that extra dose came from the same vaccine people already received. administered, or whether the additional dose is a targeted new vaccine. a particular variant, such as Omicron. To date, the primary enhancer induces immune responses similar to those produced by a specific variant enhancer in non-human primates. “Given the fact that we have a weakening immunity, we may need frequent boosters for undetermined periods of time,” says Fauci.



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