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News

Aztrazenica vaccine releases interim data showing good immune responses across all ages


 

AstraZeneca announced today that their candidate SARS-CoV-2 vaccine was creating a strong immune response both in young and old people. This answers another question about their vaccine which is critical to know. The most vulnerable population to serious complications from the virus are those over 65. To be protective, the vaccine needs to raise an immune response in this population. The company's analysis shows that a robust response was raised in both young and old involving both arms of the immune system -- B-cells (antibodies) and T-cells. I expect similar results from the other vaccine trials that are moving forward.

All vaccine candidates appear to be safe and to raise an immune response. The only question left to answer is whether the vaccine is protective. Does getting vaccinated prevent COVID-19? We will know that after the results of the trials come forward. Each company is now vaccinating 30,000 or more patients. About a third will be in a control group, with the other two thrids getting the vaccine. After subjects are vaccinated, a subset is tested for an immune response (which is what AstraZeneca just reported). The company then watches the health of the control group vs the test group. The hope is that very few of the test group get infected, while the control group does. From this, an efficacy number is calculated. Imagine that in the control group,  405 of the 10,000 get sick. While in the test group there are 200 of the 20,000 that get ill with COVID-19.

The risk of infection in the control group is 405/10,000 = 0.0405

The risk of infection in the test group is 200/20,000 = 0.01

Efficacy is then the ratio of infected in the control - infected in the test group/infected in the control...

(0.0405 - 0.01)/0.0405 = 75%

This would mean the vaccine is reducing the rate of infection by 75% and would be enough to stop the epidemic cold. Fingers crossed.