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- In an interview about coronavirus vaccines and COVID-19 prevention, a Moderna executive said current data does not yet prove that vaccines prevent a person from being infectious after contracting the virus.
- Tal Zaks told Axios that the drug prevents people from getting severely ill or even sick at all when catching COVID-19, but it’s unclear if they can still spread the disease.
- Infection after vaccination is still a possibility, but the goal of vaccines is to prevent severe illness that can lead to life-threatening complications.
Three novel coronavirus vaccines have shown they can prevent COVID-19 infection or severe illness. These are the Pfizer/BioNTech, Moderna, and AstraZeneca/Oxford drugs that proved they can deliver the expected immune response in patients, which would reduce the risk of severe COVID-19 and death. As Dr. Anthony Fauci explained recently, that’s going to be the first goal of vaccines, not blocking infection completely. Some vaccines may be able to stop the infection, but others won’t and that’s fine. What they will do is prevent the virus from doing the kind of damage seen in people who develop severe COVID-19. Various immune system components created after vaccination, like neutralizing antibodies and coronavirus-specific B and T cells, will allow the body to fight the pathogen from the moment it enters the body instead of after it has already begun replicating rapidly.
This means vaccinated people who carry the virus might still be infectious to others. Moderna’s chief medical officer Tal Zaks made that point clear in an interview, saying that the data can’t yet prove that a vaccine will stop individuals from spreading the disease.
Zaks spoke to Axios about Moderna’s mRNA drug which proved to be 94.5% effective according to interim data from the company’s Phase 3 trial. When discussing vaccines for children, Zaks said he estimates that kids will be able to get COVID-19 vaccines at some point in the middle of 2021, adding that he hopes they’ll get it before the next school year. His answer led to a second question from Axios that asked specifically if unvaccinated children can return to schools once the staff is vaccinated.
That’s when Zaks made it clear exactly what it means when someone is vaccinated, according to the data available so far.
“I think we need to be careful, as we get vaccinated, not to over-interpret the results,” the Moderna exec said. “Our results show that this vaccine can prevent you from being sick and can prevent you from being severely sick. They do not show that they prevent you from potentially carrying this virus transiently and infecting others.”
Zaks continued, “When we start the deployment of this vaccine, we will not have sufficient, concrete data to prove that this vaccine reduces transmission. Do I believe it reduces transmission? Absolutely, yes. And I say this because of the science. But absent proof, I think it’s important that we don’t change behaviors solely on the basis of vaccination.”
Health experts including Dr. Anthony Fauci have said a number of times that current health measures will remain in place once vaccinations start, and they’ll have to be observed at least until the end of 2021. Face masks and social distancing will be required for people who are vaccinated as well, and that’s because the vaccines won’t be 100% effective. Some people will still get sick and might develop a more serious form of the illness.
Zaks’s answer adds another piece to the puzzle. If a vaccinated person contracts the virus and can be infectious to others, he or she will have to wear protective gear. While the exec referred to the drug that Moderna conceived, it’s likely the same will be true of other vaccines. The vaccine makers and public health experts managing vaccination campaigns will probably have more answers once the vaccines are ready to roll out.
But even if a vaccinated individual can contract the virus and is infectious to others, he or she would likely be infectious for a shorter period of time. Current guidelines say a person with COVID-19 is infectious 2-3 days before the onset of symptoms and for as long as 8-10 days after that. A vaccine would teach the immune system how to kill the virus prior to an infection, so the pathogen will be neutralized much faster. This would reduce the virus’s ability to multiply rapidly — and the less virus that’s in the body, the less infectious a person would be.
The bottom line is that vaccines will reduce the spread of the virus. If vaccinated individuals who catch COVID-19 are indeed still infectious, it will be for a much shorter period. And it goes without saying that the more people get vaccinated, the quicker the virus will stop spreading in communities.
The Axios segment about COVID-19 prevention after vaccination follows below.

Chris Smith started writing about gadgets as a hobby, and before he knew it he was sharing his views on tech stuff with readers around the world. Whenever he’s not writing about gadgets he miserably fails to stay away from them, although he desperately tries. But that’s not necessarily a bad thing.
Michael Novakhov – SharedNewsLinks℠