Trial tweaks eyed to give Oxford vaccine a boost

Top News | 24 Nov 2020

AstraZeneca will start discussions this week with the US Food and Drug Administration to change the design of its experimental Covid-19 vaccine trial to add a likely more effective dosage regime, a senior executive says.

The British drugmaker yesterday released interim data from late-stage trials that showed the shot was on average about 70 percent effective in preventing coronavirus.

Rival vaccines from Pfizer and Moderna earlier reported that their vaccines had efficacy rates of 95 percent and 94.5 percent, respectively.

AstraZeneca's vaccine, developed by Oxford University was 90 percent effective in preventing Covid-19 when it was administered as a half dose followed by a full dose at least one month apart, according to data from the late-stage trials in Britain and Brazil.

But efficacy fell to 62 percent when it was given as two full doses at least one month apart.

Meanwhile, scientists testing the efficacy of AstraZeneca's vaccine said they cannot be sure if the virus will mutate in a way that would make it necessary to repeat vaccination every year.

But for now that looks unlikely, they added.

"We don't know yet if this virus will be mutating away from the immune response," Oxford vaccine group's director Andrew Pollard said.

"There is no evidence of that yet."

Asked whether the vaccine would be likely to give longer-term protection, Pollard said: "We've got optimism about immune response lasting at least a year," but that trials needed more time to be able to give any confirmation of durability.

No serious safety events related to the vaccine have been confirmed and it was well tolerated across both dosing regimens, AstraZeneca said.

The overall effectiveness was lower when measured across different dosing regimes, giving an apparent initial advantage to rival vaccines from Pfizer and Moderna.

But scientists also noted there may be advantages to AstraZeneca's vaccine.

"Importantly, from what we have heard, the vaccine seems to prevent infection, not just disease. This is important, as the vaccine could reduce the spread of the virus as well as protect the vulnerable from severe disease," said Peter Horby, a professor of emerging infectious diseases and global health at the University of Oxford.

He also noted that the Oxford vaccine "can be stored in the fridge, as opposed to the freezer like the other two vaccines, which means it is a more practical solution for use worldwide."

In the United States, approval for distributing the vaccine produced by Pfizer and partner BioNTech could come as soon as December 11, the top adviser for Operation Warp Speed said.


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