Sebastián De Toma joined the Pfizer clinical trial last year and received his vaccinations in August and September. The Argentine journalist is still not sure whether he received the real covid-19 vaccine or the placebo, but on Sunday, January 31, doctors in the trial called him with a new offer.
Would De Toma be ready to have a series of nasal swabs for regular testing for the virus? He says doctors offered to send Cabify (a Spanish shared transport service) to take him to the military hospital in Buenos Aires. “They’ll clean me on the go, through the car window, and that’s it,” De Toma says.
The additional coronavirus tests, which are offered to some volunteers in Argentina and the United States, are part of a plan by Pfizer to help address a key unknown covid: How often vaccinated people develop asymptomatic infections by coronavirus and whether they can still spread the virus despite the vaccine.
Whether or not vaccines stop the “progressive transmission” of the virus will likely be a critical variable in determining how the pandemic develops and how quickly life returns to normal. Right now, researchers say, their best guess is that vaccines will reduce transmission, but they may not prevent it completely.
“We don’t know, but it’s an important question because the answer will influence the use of the mask; it will influence behavior; it’s about the convenience of going to restaurants and the movies and the overall benefit that we can expect from vaccines, ”says Lawrence Corey, who heads operations for the Covid-19 Prevention Network, which has conducted several vaccine trials in states -United.
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“A vaccine can do three things: stop you from contracting the disease completely, stop transmission, and stop symptoms,” says Jeffrey Shaman, a public health researcher at Columbia University. A perfect vaccine would create what is called “sterilizing” immunity, which means that the virus cannot establish itself in your body at all. Some vaccines, however, allow low-level infections that people’s immune systems fight off without any symptoms. Their bodies still accumulate a certain amount of the virus, which they can pass on to other people.
The reason why we don’t know how well vaccines stop this transmission is because it is expensive and complicated to measure. When companies like Pfizer, Novavax, Moderna Therapeutics and others launched large studies on their new covid-19 vaccines last year, they were testing whether vaccines could prevent people with the disease from getting sick or to die. The results of this count were impressive: almost no vaccinated person ends up in an intensive care unit on a ventilator.
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