Can vaccinated people transmit the coronavirus?


1. Does vaccination completely prevent infection?

The short answer is no. You can still get infected after you have been vaccinated. But your chances of getting seriously ill are slim to none.

Many people think that vaccines work as a shield, preventing a virus from infecting cells completely. But in most cases, a person who gets vaccinated is protected against disease, not necessarily infection.

Everyone’s immune system is a little different, so when a vaccine is 95 percent effective, that just means that 95 percent of the people who get the vaccine won’t get sick. These people could be completely protected from infection, or they could be infected but remain asymptomatic because their immune system clears the virus very quickly. The remaining 5 percent of vaccinated people can become infected and become ill, but it is highly unlikely that they will be hospitalized.

Vaccination does not 100 percent prevent you from getting infected, but in all cases it gives your immune system a huge advantage over the coronavirus. Whatever your outcome, be it complete protection against infection or some level of disease, you will be better off after finding the virus than if you had not been vaccinated.

2. Does infection always mean transmission?

Transmission occurs when enough viral particles from an infected person enter the body of an uninfected person. In theory, anyone infected with the coronavirus could transmit it. But a vaccine will reduce the chance of this happening.

Jennifer Simon, an elementary school speech-language pathologist, poses last month in Nashville, Tennessee, to display the branding of the adhesive bandage where she received her COVID-19 vaccine. Simon and a fellow teacher took a sick day at their schools and made a four-hour round trip to rural Van Buren County in Tennessee to get vaccinated. Mark Humphrey / Associated Press

In general, if vaccination does not completely prevent infection, it will significantly reduce the amount of virus that leaves the nose and mouth (a process called shedding) and shorten the time the virus is shed. This is a big problem. A person who sheds less virus is less likely to transmit it to another person.

This appears to be the case for coronavirus vaccines. In a recent pre-print study that has yet to be peer-reviewed, Israeli researchers screened 2,897 vaccinated people for signs of coronavirus infection. Most did not have a detectable virus, but people who were infected had a quarter as much virus in their bodies as unvaccinated people who were tested at similar times after infection.

Fewer coronavirus viruses means less chance of spreading it, and if the amount of virus in your body is low enough, the chance of transmitting it can reach almost zero. However, researchers don’t yet know where that cutoff is for the coronavirus, and since vaccines don’t provide 100 percent protection against infections, the Centers for Disease Control and Prevention recommends that people continue to wear masks. and social distance even after I have been vaccinated.

3. What about the new variants of the coronavirus?

New variants of coronavirus have emerged in recent months, and recent studies show that vaccines are less effective against certain, such as the B1351 variant first identified in South Africa.

Every time SARS-CoV-2 replicates, it gets new mutations. In recent months, researchers have found new variants that are more infectious, meaning that a person needs to inhale less virus to become infected, and other variants that are more transmissible, meaning that they increase the amount of virus a person sheds. . And researchers have also found at least one new variant that appears to be better at evading the immune system, according to early data.

So how is this related to vaccines and transmission?

For the South African variant, the vaccines still provide more than 85 percent protection against severe COVID-19 disease. But when mild and moderate cases are counted, they provide, at best, only about 50 to 60 percent protection. That means that at least 40 percent of vaccinated people will still have a strong enough infection, and enough virus in their body, to cause at least moderate illness.

If vaccinated people have more viruses in their bodies and it takes less of that virus to infect another person, there will be a greater chance that a vaccinated person can transmit these new strains of the coronavirus.

If all goes well, vaccines will very soon reduce the rate of serious illness and death around the world. To be sure, any vaccine that reduces the severity of the disease also reduces, at the population level, the amount of virus that is shed overall. But due to the emergence of new variants, vaccinated people still have the potential to spread and transmit the coronavirus to other people, vaccinated or not. This means that vaccines are likely to take much longer to reduce transmission and for populations to achieve herd immunity than if these new variants had never emerged. The exact time it will take is a balance between how effective the vaccines are against the emerging strains and how transmissible and infectious these new strains are.

The Conversation is an independent, non-profit source of news, analysis, and commentary from academic experts. This article has been republished from The Conversation under a Creative Commons license. Read the original article here.


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