In early March more than 6200 doses of the new one do Covid-19 vaccine from Johnson and Johnson were supposed to be transported to the city of Detroit, Michigan. The Mayor, saying,” Moderna and Pfizer are best”, refused the shipment of the vaccines.
A vaccine’s efficacy rate is calculated in large clinical trials when the vaccine is tested on tens and thousands of people, these people are broken into two groups, half get a vaccine and half get a placebo. Then they are sent out to live their lives, while scientists monitor whether or not they get Covid -19 over several months. In the trial for Pfizer/BioNTech for example, there were 43,000 participants.
In the end, 170 people were infected with Covid-19. And how those people fall into each of these groups determines a vaccine’s efficacy. If the 170 people were evenly split, that you are just as likely to get sick with the vaccine as without it, so it would have 0% efficacy. If all 170 were in the placebo group and zero people who got the vaccine were sick, the vaccine would have an efficacy of 100%.
With this particular trial, there were 162 in the placebo group and just 8 in the vaccine group. It means those who have the vaccine were 95% less likely to get Covid-19. The vaccine had a 95% efficacy. Now, this doesn’t mean that if 100 people are vaccinated, 5 of them will get sick. Instead, that 95% number applies to the individual. So each vaccinated person is 95% less likely than a person without a vaccine, to get sick, each time they are exposed to Covid-19.
“Any vaccine you’re offered right now is the best vaccine. With each shot that goes into someone’s arm we get closer to the end of this pandemic”, says Deborah H Fueller, a researcher from the University of Wisconsin System.
Text by: Sreyoshi Sil, IBTN9
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