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Coronavirus US: is a third dose of the Pfizer vaccine necessary?

Over 205 million Americans have received at least one dose of the Covid-19 shot and almost 54 million are fully vaccinated. Will a third shot be needed?

Coronavirus US: is a third dose of the Pfizer vaccine necessary?

According to the latest data by Johns Hopkins University, 205,871,913 Americans have received at least one dose of the Covid-19 shot and 74,621,644 people or 22.81% of population are now fully vaccinated after having received two shots of the vaccine.

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However, there has been suggestions that a third, booster shot may be necessary before the flu season starts if coronavirus isn’t under control. According to a recent study conducted by the University of Birmingham, spike-specific antibodies were present in 93% of people after both shots of the Pfizer vaccine. Those antibodies, along with ‘helper’ CD4+ T cells, ‘killer’ CD8+ T cells and memory B cells can recognize and kill viruses if they are encountered again but how long immunity from Covid-19 lasts is still not known. A recent study published in the February edition of Science magazine claims that immunity memory from Covid-19 lasts up to eight months. 70% of individuals possessed detectable CD8+ T cell memory one month after infection but that proportion declined to 50% six to eight months after infection.

While durable immunity against secondary Covid-19 disease could be a possibility for most individuals, Pfizer CEO Albert Bourla has admitted that some people may require a booster shot. He told CNBC earlier this month, “A likely scenario is that there will be likely a need for a third dose, somewhere between six and 12 months and then from there, there will be an annual revaccination, but all of that needs to be confirmed. And again, the variants will play a key role”.

"We'll know more by the end of the summer" - Fauci

That viewpoint isn’t being totally ruled out by director of the US National Institute of Allergy and Infectious Diseases Dr. Anthony Fauci, who says that decisions on booster vaccinations will be made once we know more about the immune system’s ability to recognise and fight Covid-19. Fauci told NBC News' Meet the Press on Sunday that decisions on vaccine boosters will not be made by the likes of Pfizer or Astrazeneca but at government level.

“It’s going to be a public health decision; it’s not going to be a decision made by a pharmaceutical company. We are partners with them because they are supplying it. It will be an FDA-CDC decision,” Dr. Fauci explained. “The CDC will use their advisory committee in immunization practices the way they always do, and what we will do is, we will look at the durability of the response – namely, measure the antibodies, hopefully very soon we will get a good correlate of immunity, and if the correlate goes down, and you see it start to slope down, you could project when it’s going to be so low that you might have a danger of having breakthrough infections. When that happens, clearly, you’re going to see a recommendation for a boost. The other thing, is that you might start seeing more breakthrough infections that go beyond the level of the efficacy of the vaccine, and then, you might also make a decision to do it. But it will be a public health-based decision – not a pharmaceutical company-based decision.

As for when we might know if a booster vaccine will be necessary or not, Fauci concluded, “It depends on how the slope of that curve goes down. My projection, just from my own experience, I think by the end of the summer and the beginning of the fall, we will know and have a pretty good idea about whether we need the boost”.

Moderna CEO Stephane Bancel has confirmed that the company hopes to have a booster shot for its two-dose vaccine available by the autumn.


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