Filenews 8 December 2020
At least three candidate vaccines against Covid-19 seem to offer high levels of protection, but it is still unclear whether they prevent the dispersal of the coronavirus.
Clinical trials of vaccines continuing around the world were designed to record only the number of volunteers who show symptoms of the disease. This leaves open the possibility that some volunteers will become infected without exhibiting symptoms and thus spread the virus unknowingly.
"A lot of people think that once they get the vaccine, they won't have to wear a mask anymore," Michael Tal, an anaesthesiologist at Stanford University, tells the New York Times.
"It is critical that they understand that they should continue to wear it because they may be transmitting the virus," he says.
Antibodies in the nose, antibodies in the blood
In most respiratory infections, including Covid-19, the nose is the main route of entry. When the virus reproduces in the nose, the immune system responds with a special class of antibodies produced specifically in the mucosa.
For this reason, nose vaccines are considered more effective than intramuscular vaccines. In the future, such vaccines could also become available for the coronavirus.
Today's candidate vaccines are administered by intramuscular injection and cause the production of antibodies that circulate freely in the bloodstream. Some of these antibodies reach the nose, but how much remains unknown.
If the antibodies of the nose are not sufficient, the virus could find the opportunity to multiply in the mucosa even if it does not cause symptoms.
"Prevention of serious disease is the easiest. Preventing mild disease is more difficult and preventing any infection is the most difficult of all," says Deepa Batatsar, an anaesthesiologist at the University of Arizona.
"If a vaccine is 95% in the prevention of disease with symptoms, it will certainly be far less effective at preventing any infection," he points out.
Antibodies N
The question of how many vaccinated volunteers are affected by the coronavirus without symptoms will not be answered by clinical trials, but subsequent studies are expected to provide a definitive answer.
Pfizer, for example, will test a portion of volunteers for antibodies targeting the virus's N protein. Since vaccines have nothing to do with this protein, the presence of N antibodies would reveal any cases of infection after vaccination.
So will Moderna, but to all volunteers. "It will take several weeks before this data becomes available," a spokesman for the US biotechnology company told the newspaper.
In addition, Dr. Tal's team at Stanford plans to examine samples of volunteers from the Johnson & Johnston clinical trial to determine whether the levels of antibodies in the nose are comparable to the levels of antibodies in the blood.
One such study already published in Science concluded that antibody levels are comparable in the blood and nose, which may mean that vaccination prevents the virus from spreading.
However, a single study is not enough to give a definitive answer.
Until sufficient data is gathered, the masks must remain in place.
Source: in.gr
