December 8th that foreign media said that all the announcements of pharmaceutical companies on their COVID-19 vaccines emphasize efficiency. Modena claims that its vaccine is 94.1%, Pfizer is 95%, and AstraZeneca is 70%. But what does it mean to be efficient?
These figures were obtained by comparing the number of people who showed symptoms of COVID-19 in the placebo group and the vaccination group. That said, efficiency is the chances of protecting people from symptoms of COVID-19 rather than infection.
According to the Spanish daily news website on December 5, volunteers have not been tested for regular nucleic acid in the third phase of Pfizer and Modena, so no asymptomatic cases have been actively tested.
This decision was made mainly for three considerations: simplifying and facilitating the progress of clinical trials (with thousands of people participating); focusing on the most important topics (vaccines safety and preventing serious diseases); and overcoming the lack of testing tools faced by many countries.
However, AstraZeneca’s trials in England and Brazil were sampled weekly to detect asymptomatic infections. However, the company has not released specific data on this aspect of the vaccine, indicating only indications that there are a small number of asymptomatic patients in the vaccinated population.
Therefore, at present, we only know that the vaccine can avoid people from developing symptoms of COVID-19 and the resulting death in the short term, but we do not know its effectiveness in avoiding infection with the virus.
Why is the efficacy of vaccines in preventing COVID-19 infection uncertain? Because some vaccinated people may become asymptomatic spreaders, the immunity he acquires, while enough to avoid his own illness, is not enough to avoid infection and spread to others. In any case, if a vaccine can avoid disease, it should also avoid contracting the virus to a certain extent, but we don’t know the exact extent, which means that we will face uncertainty in this regard in the future.
According to the report, one of the basic reasons for the spread of COVID-19 to almost all over the world is the spread of asymptomatic patients. What percentage of vaccinators will become asymptomatic spreaders without knowing it? At present, we are not clear about this, so we can’t expect the extent to which vaccination can stop the spread of COVID-19 around the world.
The report pointed out that if the precautionary principle is followed, vaccinators must continue to take preventive measures such as wearing masks, maintaining social distancing, paying attention to hand hygiene, maintaining indoor ventilation and avoiding access to closed and crowded places to avoid infection.
Until data are available on how effective vaccines are avoiding infections, and how long-term effects of vaccines, it is difficult to know how long restrictions will last, or when society will return to normal. The timing of herd immunity acquired through vaccines depends on the effectiveness of the vaccine in avoiding infection.
Considering the importance of this issue, Pfizer and Modena have considered testing the effectiveness of vaccines in preventing infection in future clinical trials of vaccines.
It can be predicted that AstraZeneca will release information on this issue in the next few months, because they have designed a link to detect asymptomatic patients in the trial, and it is believed that enough results can be collected within a certain period of time to determine the efficacy of this aspect.
Ultimately, the end of the pandemic depends not only on when millions of doses of coronavirus vaccine can be vaccinated, but also on their effect on reducing infection and how long immunity lasts, the report believes.