Saturday , January 16 2021

Two vaccines with good results; one with more questions than answers



Australia has signed contracts to buy tens of millions of doses of the AstraZeneca and Pfizer vaccines, and has potential access to the Moderna vaccine through an international agreement.

“It’s good enough to be very optimistic about how this is all going,” said Professor Terry Nolan, head of the vaccine and immunization research group at the Doherty Foundation and the Murdoch Children’s Research Institute.

“It turned out better than we had imagined. It is quite possible that all these events would fail.

“But I would advise people not to base any sound decisions on press releases and no data.”

The companies have not yet published their results in peer-reviewed academic journals.

Science-by-press-statement has gone wrong before: remdesivir the first approved treatment for COVID-19 came after promising press results, but later independent studies suggest it is not working at all.

Nevertheless, it is not surprising that Moderna and Pfizer vaccines first crossed the finish line, said James Triccas, University of Sydney Professor of medical microbiology.

A research associate works at the laboratory of Moderna Therapeutics Inc.  in Cambridge, Massachusetts.

A research associate works at the laboratory of Moderna Therapeutics Inc. in Cambridge, Massachusetts.Credit:Bloomberg

Both companies are developing mRNA vaccines; these vaccines contain genetic instructions for our cells, which read them and then produce small copies of SARS-CoV-2 pig protein, prompting the immune system to respond.

“They are designed for the simplicity and speed of development and manufacturing. You can make these vaccines pretty quickly, ”said Professor Triccas.

Some scientists speculate that mRNA vaccines are less likely to produce long-lasting immunity, because they don’t actually mimic a natural infection. But we’re years away from knowing that.

“They have no idea. We all speculate, ”said Professor Nolan. “In fact, for a disease that could kill you … if we are concerned about whether a vaccine will only last two years, we have better things to worry about.”

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Meanwhile, AstraZeneca’s initial headline results – 90 percent effectiveness – look great. But under further scrutiny, they have begun to unravel.

It soon became clear that the 90 per cent efficacy mark by a small group of patients had been accidentally given the wrong dose of vaccine. This group was generally younger; vaccines generally do not work as well in older people.

In patients receiving the correct dose, efficacy was only 62 percent, although no serious cases of infection were reported.

Sometimes looking at a small group is just a trial, rather than the general results, because it can allow scientists to skew the results in a way that suits their arguments.

It is not yet clear what underpins these unexpected results.

This photo, May 4, 2020, shows the first patient enrolled in the clinical trial of the Pfizer COVID-19 coronavirus virus vaccine at the University of Maryland School of Medicine in Baltimore.

This photo, May 4, 2020, shows the first patient enrolled in the clinical trial of the Pfizer COVID-19 coronavirus virus vaccine at the University of Maryland School of Medicine in Baltimore. Credit:AP

The AstraZeneca vaccine contains innocent chimpanzee virus that has been genetically modified to look similar to SARS-CoV-2.

Scientists had expected that this would mean that a two-dose regimen would not work well, as the vaccine could cause immunity to develop to SARS-CoV-2 and the vaccine itself.

“You can’t effectively give them more than once because you raise an immune response to the vector. The next time you donate, your body wants to clear it just like any other virus. It really just needs to work well with a single dose, ”said Professor Colin Pouton, who is leading the COVID-19 vaccine project at Monash University.

But accidental underdosing at the first injection may be avoiding this problem, says Professor Triccas.

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