On Monday, AstraZeneca and Oxford released details about the first 131 volunteers to get COVID-19 in late-stage trials in the United Kingdom and Brazil. All of the volunteers got two doses about a month apart, but in some cases the first dose was only at half strength.
Surprisingly, the vaccine combination in which the first dose was only at half strength was 90% effective at preventing COVID-19 in the trial. In contrast, the combination of two, full-dose shots led to just 62% efficacy.
Why would that be?
No one knows. The researchers speculated that the lower first dose did a better job of mimicking the experience of an infection, promoting a stronger immune response. But other factors, like the size and makeup of the groups that got different doses, may also be at play.
Why did the researchers test two different doses?
It was a lucky mistake. Researchers in Britain had been meaning to give volunteers the initial dose at full strength, but they made a miscalculation and accidentally gave it at half strength, Reuters reported. After discovering the error, the researchers gave each affected participant the full strength booster shot as planned about a month later.
https://sg.yahoo.com/news/know-astrazenecas-head-scratching-vaccine-193851647.html
Surprisingly, the vaccine combination in which the first dose was only at half strength was 90% effective at preventing COVID-19 in the trial. In contrast, the combination of two, full-dose shots led to just 62% efficacy.
Why would that be?
No one knows. The researchers speculated that the lower first dose did a better job of mimicking the experience of an infection, promoting a stronger immune response. But other factors, like the size and makeup of the groups that got different doses, may also be at play.
Why did the researchers test two different doses?
It was a lucky mistake. Researchers in Britain had been meaning to give volunteers the initial dose at full strength, but they made a miscalculation and accidentally gave it at half strength, Reuters reported. After discovering the error, the researchers gave each affected participant the full strength booster shot as planned about a month later.
https://sg.yahoo.com/news/know-astrazenecas-head-scratching-vaccine-193851647.html