Can vaccinated people transmit the coronavirus? – The Denver Post

EDITOR’S NOTE: So you received your coronavirus vaccine, you waited two weeks for your immune system to respond to the vaccine, and you are now fully vaccinated. Does this mean that you can travel the world like old times without fear of spreading the virus? Deborah Fuller is a microbiologist at the University of Washington who works on coronavirus vaccines. She explains what the science shows about post-vaccination transmission and whether new variants could change this equation.

1. Does the vaccine 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 against infection.

Each person’s immune system is a little different, so when a vaccine is 95% effective, that just means that 95% of the people who get the vaccine will not 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% of vaccinated people can become infected and become ill, but it is highly unlikely that they will be hospitalized.

Vaccination does not 100% 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 potentially transmit it. But a vaccine will reduce the chance of this happening.

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 In a recent prepress study that has not yet been peer-reviewed, Israeli researchers screened 2,897 vaccinated people for signs of coronavirus infection. Most had no 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% protection against infection, the Centers for Disease Control and Prevention recommends that people continue to wear masks and social distance even after i’ve 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 ones, 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% protection against a serious illness from COVID-19. But when mild and moderate cases are counted, they provide, at best, only about 50% -60% protection. That means that at least 40% 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 virus 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 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. Exactly how long it will take is a balance between how effective vaccines are against emerging strains and how communicable and infectious these new strains are.

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