Sat. Oct 1st, 2022
Rows of small glass vials.
enlarge Vials of undiluted Pfizer COVID-19 vaccine.

As the pandemic continues to rise to new heights, debate has erupted among experts about how to get the most protection as quickly as possible from the limited supply of COVID-19 vaccines currently available.

Suggestions put forward so far include delaying the second of a two-dose regimen by perhaps three to four months rather than dispensing them at the scheduled three to four week intervals evaluated in large clinical trials. to investigate. With this change, more people can now get their first dose, meaning:some protection. Another possibility is simply halving the dose, which would immediately double the number of people who can now be vaccinated. And regulators in the UK have introduced the idea of ​​mixing regimens – where some people get their first dose of a vaccine from one manufacturer and then get a second dose of vaccine from another manufacturer based on availability at the time.

The evidence supporting these proposed adjustments in vaccine rollout is shaky at best. But some experts argue that the dire state of the pandemic justifies a new, perhaps more risky approach.

viral beating

†[A]Mike Tyson once said, ‘Everyone has a plan until they get punched in the mouth,'” Robert Wachter, chair of the department of medicine at the University of California at San Francisco, and Ashish Jha, dean of the Brown University School of Public Health, wrote in an op-ed published Sunday in The Washington Post, in which the couple makes an argument for delaying second doses, writing: “When it comes to COVID-19, we get hit again and again. shut up. It’s time to change the plan.”

Wachter and Jha note that researchers have not looked at what happens when a person takes just one dose of a two-dose vaccine. In the US, the Food and Drug Administration has cleared the use of Moderna’s mRNA COVID-19 vaccine and another mRNA vaccine made by Pfizer and BioNTech. In large Phase III clinical trials, both vaccines demonstrated approximately 95 percent efficacy in protecting against COVID-19, but only after two doses administered for 28 days (Moderna) or 21 days (Pfizer/BioNTech). It’s unclear how effective the vaccine is after just one dose and how long that protection can last.

The single-dose strategy “has not been studied, so we don’t know if and when immunity starts to wane from the first injection,” Jha and Wachter write. “But,” they continue, “data from Moderna, for example, is reassuring. It shows a robust immune response four weeks after the first injection, and most experts believe it is extremely unlikely that immunity would decline in some way at week eight or even week 12 after a single injection.”

Risks and unknowns

That thinking seemed enough to convince health officials in the UK. Last week they announced that they would allow the interval between the first and second injections to be 12 weeks. They also opened up the possibility that people could receive the first and second vaccine doses from different manufacturers – for example, a person could receive a first dose of the Pfizer/BioNTech vaccine, followed by a dose of a COVID-19 vaccine from AstraZeneca/University from Oxford. (The AstraZeneca vaccine is another two-dose vaccine that was approved in the UK last week. U.S. officials expect the FDA to grant it emergency clearance in the coming months.)

But other experts still strongly oppose the idea of ​​delaying a second dose. While immune responses may not “fall down” dramatically in a few months, they will decline over time. And because researchers don’t yet know what level of immune response is needed to ward off infection and disease, it’s not possible to say that one dose will be enough to prevent people from becoming infected or sick.

In addition, a declining immune response after one dose could potentially make the coronavirus more dangerous. Some experts have noted: that having the virus circulating wildly mixes with many people with weak immune responses could create the perfect selection pressure for the virus to adapt to evade those immune responses. Coronaviruses mutate naturally over time, and several variants have already emerged, including those in the UK and South Africa, which seem to spread more easily among humans. So far, those variants don’t seem to cause more serious or deadly disease. And they are not thought to evade immune responses from natural infections or the authorized vaccines. But partially vaccinating a large number of people could lead to those nightmare scenarios, some experts fear.

Stick to the science

With the uncertainties and risks involved, many experts are vehemently opposed to fiddling with the vaccine plan. That includes top infectious disease expert Anthony Fauci. Last Friday, Fauci rejected the idea that the US was following the UK’s lead by allowing a delayed second dose. “I wouldn’t be in favor of that,” Fauci said in an interview with CNN.

“The fact is, we want to stick with what the science tells us, and the data we have for both [vaccines] indicate you’re prime, followed by a boost in 21 days with Pfizer and 28 days with Moderna,” Fauci said. “And right now we’re dealing with it, and that’s the decision being made.”

Moncef Slaoui, chief scientist of the US government’s Operation Warp Speed, reiterated Fauci’s opposition to delaying second doses in an interview Sunday on CBS’ Face the nation

“We have always said that these vaccines will be developed based on science and all decisions will be made transparently based on data,” Slaoui said. “Changing the decisions made, the choices made, which is to give two doses of vaccine — the second dose gives you a ten times higher immune response than the first dose — without any data that I don’t think would be responsible.”

Intriguingly, though, Slaoui offered another alternative to maximize vaccine rollout:

“Here’s the alternative. We know that for the Moderna vaccine, giving half the dose to people between the ages of 18 and fifty-five — two doses, half the dose, which means exactly reaching the goal of immunizing double the number of people. with the doses we have – we know it induces an identical immune response to the one hundred microgram dose and that’s why we’re in talks with Moderna and with the FDA.

“Ultimately, of course, it will be an FDA decision,” Slaoui said. But, he added, “I think that’s a more responsible approach that will be based on facts and data.”

By akfire1

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