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This is not just an academic problem. Depending on how people perceive the meaning of these numbers, what they think about the vaccine, about the desire to get vaccinated and about behavior after the vaccine. All of these things affect the overall management of a pandemic, writes Live Science.
So how should these numbers be interpreted?
“I think it is very important that people understand that this is an extremely effective vaccine. It’s much more effective than it looks, “said Brianne Barker, a virologist at Drew University in the United States, of the Pfizer vaccine.
One of the common misperceptions is the assumption that 5% of Pfizer clinical trials vaccinated people developed COVID-19. However, that’s not true. The actual percentage of people with COVID-19 after vaccination, in both the Pfizer and Moderna studies, is up to 100 times lower (0.04 percent).
So what does that 95 percent mean? The fact that vaccinated people had a 95 percent lower risk of developing a symptomatic form of COVID-19 than those in the control group (that is, they were not vaccinated against COVID-19 even though they did not know it). In other words, vaccinated people in Pfizer’s clinical trials were 20 times less likely to have COVID-19 than unvaccinated people.
And that means that this vaccine is “one of the vaccines available to humanity in general,” Barker said. By comparison, the MMR trivalent measles, rubella, and mumps vaccine after two doses, according to the US Center for Disease Control and Prevention, is 97 percent effective. efficacy against measles, 88 percent. efficacy against mumps. The effectiveness of a vaccine against seasonal flu ranges from 40 to 60 percent (the variation depends on the annual variation of the virus strain), but according to the same Center for Disease Control and Prevention in the United States only in 2019-2020. 7.5 million protected season. cases of influenza.
So if efficacy is viewed as a certain percentage of how much the likelihood of COVID-19 cases decreases, what counts as a COVID-19 case?
For both Pfizer and Moderna, a case is defined as a patient experiencing at least one symptom of the disease, regardless of the severity of that symptom, and the patient has a positive COVID-19 test. In Johnson & Johnson’s case, a ‘case’ is recorded if the virus test is positive and the patient has at least one ‘moderate’ symptom (shortness of breath, decreased oxygen saturation, changes in respiratory rhythm) or at least two ‘mild symptoms (fever, cough, fatigue, headache, nausea). By this definition, a COVID-19 patient may feel ill or be bedridden for several weeks. In the case of AstraZeneca, the case was reported after a positive SARS-CoV-2 test and one of the symptoms of the disease (fever above 37.8 ° C, cough, shortness of breath, loss of taste or smell) .
Mr. Barker cautions against direct comparisons of vaccine effectiveness: studies with Johnson & Johnson, Pfizer and Moderna and AstraZeneca have been conducted in geographically different locations with different populations, with slightly different times; which may have led to differences in the COVID-19 variants circulating in the population at that time. “At the time of the Johnson & Johnson vaccine research, the British variant of the virus and other variants were more common than at the time of Modern research,” said the virologist.
Additionally, asymptomatic COVID-19 cases were not counted in any of the clinical trials. “All efficacy figures show protection against symptoms, not protection against infection,” Barker explained (although there is now preliminary evidence that the Pfizer and Moderna vaccines also reduce the number of virus particles in humans and a positive result of the proof). no such conclusions have been reached yet, it is too early to rule out masks after vaccination).
However, in all of these studies, there was a second and possibly more important definition of ‘case’. Medical systems are not concerned with mild symptoms of illness, but with illness that requires the patient to be hospitalized or the patient to die. Therefore, in addition to the nominal efficacy endpoint, there was a severe case protection measure (showing how well subjects were protected from conditions that severely affected their heart or respiratory system, requiring supplemental oxygen, in the intensive care unit). causes respiratory failure or death).
And by this criterion, all vaccines (Pfizer, Moderna, Johnson & Johnson, and AstraZeneca) were 100%. effective in protecting patients from serious illness as early as 6 weeks after the first dose (in the case of Moderna) and 7 weeks after Pfizer and Johnson & Johnson. Weeks after the first dose.
“We are incredibly fortunate to have achieved this level of vaccine effectiveness,” Barker said.
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