![covid-vaccine-bcl](https://img.etimg.com/thumb/msid-79380320,width-300,height-225,imgsize-255311,resizemode-75/covid-vaccine-bcl.jpg)
While Moderna and Pfizer have reported over 95% efficacy, the AstraZeneca-Oxford vaccine has a rate of up to 90% and an average of 70.4% if results of two different dosing regimes are combined.
In contrast, the Ebola vaccine efficacy in trials was 50% while that for most flu vaccines it is around 65%. Polio, Measles, tetanus vaccines have an efficacy of around 70%.
Anthony Fauci, top infectious disease expert in the US, had said the over 90% efficacy of Pfizer vaccine candidate ‘is just extraordinary’ and would have a “major impact” going ahead.
Efficacy of a vaccine measures its success in preventing the disease in large scale trials in a group given vaccine compared to the group that received a placebo. A vaccine's effectiveness, on the other hand, is known after many years of use in the general population.
Most vaccines for respiratory viruses are not 100% effective, but an efficacy of over 50% is seen enough to stop a pandemic by providing a substantial herd immunity.
Efficacy of over 50% for these vaccines, if approved by regulators after seeing all the evidence, should ensure rapid progress against Covid-19 if they are rolled out quickly and cover a substantial population.
On Monday Astrazeneca-Oxford announced that their Covid vaccine ChAdOx1 nCoV-2019, is effective at preventing COVID-19 infection and offers a high level of protection.
The company said that Phase 3 interim analysis of 131 Covid-19 cases indicated that the vaccine was 70.4% effective when combining data from two dosing regimens.
The first was two dose regimen which showed a 63% efficacy and the second trial where the doses were halved in first dose and later given a standard second dose after a 52 day gap showed that the vaccine showed 90% efficacy, giving a combined efficacy of 70.4%
Moderna and Pfizer candidates displayed efficacy of over 95%.
“Even though the headlines say 70% efficacy the subgroup of 3000 participants where we gave half dose as a primer and the second shot as full dose showed 90% efficacy,” said Andrew Pollard, Director of the Oxford Vaccine Group and Chief Investigator of the Oxford Vaccine Trial.
“The vaccine can be stored at a usual fridge system which makes it easy to be distributed across the world.”
Since the vaccine works best as half and full dose, a higher supply would be available as manufacturers had planned the vaccine as a double shot one.
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