Allergic reactions to these vaccines are low, according to the CDC 2:20
(CNN Spanish) – The efficacy of vaccines against covid-19 has been evaluated in various studies. Now, scientists measure their effectiveness against contagion.
Two studies conducted in the United States measure how effective the Pfizer / BioNTech and Moderna vaccines are in reducing the spread of COVID-19.
You can listen to this episode on Apple Podcasts, Spotify, or your favorite podcast platform, or read the transcript below.
Hello, I am Dr. Elmer Huerta and this is your daily dose of information about the new coronavirus, information that we hope will be useful to take care of your health and that of your family.
The news about the effectiveness of vaccines against covid-19 is encouraging.
Let us first of all remember that – as we said in the episode of March 4 – we must differentiate between efficacy and effectiveness of vaccines.
What is efficiency?
The efficacy of a vaccine – those numbers we’ve heard of 95% from Pfizer / BioNTech, or 94.5% from Moderna – is calculated in a phase 3 controlled clinical trial in which you choose what kind of volunteers to participate, and the vaccine is compared against a placebo.
Efficacy means that – compared to a placebo – people who received a vaccine were, for example, 95% less likely to develop the disease.
What is effectiveness?
On the other hand, effectiveness is calculated by vaccinating all types of people in real life, that is, it is the consequence of measuring how a vaccine works in a community vaccination program – no longer in a controlled clinical trial – and those vaccinated against the unvaccinated.
Here, a 95% effectiveness means that – compared to the unvaccinated – vaccinated people were 95% less likely to get sick.
Without a doubt, effectiveness studies are very important, because they tell us whether the vaccine is working or not in the place that really matters: in the communities.
In this regard, two recent studies of effectiveness in health workers in the United States are published in The New England Journal of Medicine on Tuesday, and both give us very good news: the Pfizer / BioNTech and Moderna vaccines are very effective in reducing contagions of the new coronavirus.
Study 1: Vaccine Effectiveness in California Workers
The first, done in health systems workers at the University of California, San Diego and the University of California, Los Angeles, show that the rate of new infections among staff dropped dramatically, beginning the second week after it was administered. the first dose.
The study showed that only 2.5% of vaccinated people who had a molecular test within the first week – after the first dose – had a positive result.
For its part, this positivity was only 1.6% for those vaccinated who underwent the test in the second week, and 0.7% for those who did it in the third week.
For those who completed their second dose, 0.4% had a positive molecular test during the week after the second dose was given, and less than 0.2% in the second week after the second dose.
In other words, as the vaccinated person was given the opportunity to produce more antibodies, the greater the protection provided by the vaccine.
Study 2: Vaccine Effectiveness in Workers in Texas
The second study, conducted at the University of Texas Southwestern Medical Center in Dallas, where workers were vaccinated during the largest increase in COVID-19 cases the region had ever seen, showed that 2.61% of the Non-vaccinated employees developed the infection, compared to 1.82% for partially vaccinated workers and only 0.05% for fully vaccinated employees.
Without a doubt, that 52 times greater protection against the probability of infection between vaccinated and unvaccinated is impressive.
That high vaccine effectiveness reduced the number of employees who had to isolate or quarantine by more than 90%, preserving the workforce when it was most needed, amid the pandemic, Dr. William Daniel of the University Medical Center.
The hope is that the encouraging effectiveness that is being documented in these studies is also replicated in the communities where the vaccines are being applied.
With that kind of effectiveness, it is possible that, if at least 80% of people are vaccinated promptly, the much-desired herd, group, herd or herd immunity can be achieved, and the pandemic can be controlled.
Do you have questions about the coronavirus?
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