So you got your coronavirus vaccine, waited two weeks for your immune system to respond to the shot, and are now fully vaccinated. Does this mean you can move around the world as you used to without fear of spreading the virus?
D.Eborah Fuller is a microbiologist at the University of Washington Medical School working on coronavirus vaccines. She explains what science shows about post-vaccination transmission – and whether new variants could change that equation.
1. Does the vaccination completely prevent infection?
The short answer is no. You can still get infected after vaccination. But your chances of getting seriously ill are almost zero.
Many people believe that vaccines act like a protective shield, preventing a virus from infecting cells altogether. But in most cases a person who is vaccinated is Protected from disease, not necessarily from infection.
Everyone’s immune system is slightly different, so when it comes to a vaccine 95% effectiveThat means only 95% of the people who will receive the vaccine don’t get sick. These people could be completely protected from infection or become infected but remain asymptomatic as their immune systems clear the virus very quickly. The remaining 5% of people who are vaccinated can, but are, infected and get sick They are extremely unlikely to be hospitalized.
Vaccination doesn’t 100% prevent you from getting infected, but either way it does give your immune system a huge head start over the coronavirus. Regardless of your outcome – whether full protection from infection or some degree of disease – you will be better off after the virus emerges than if you hadn’t been vaccinated.
2. Does infection always mean transmission?
Transmission occurs when enough virus particles from an infected person get into the body of an uninfected person. In theory, anyone infected with the coronavirus could potentially transmit it. However, having a vaccine will make this less likely to happen.
Generally, if vaccination doesn’t completely prevent infection, it will greatly reduce the amount of virus that comes out of your nose and mouth – a process known as shedding – and the time it takes for you to shed the virus. This is a big deal. A person who gives off fewer viruses is less likely to pass it on to someone else.
This appears to be the case with coronavirus vaccines. In one current preprint study The Israeli researchers tested 2,897 vaccinated people for signs of coronavirus infection. Most had no detectable virus, but people who were infected had a quarter the amount of virus in their bodies than unvaccinated people who were tested at similar times after infection.
Fewer coronavirus viruses mean a lower chance of spreading it. If the amount of virus in your body is low enough, the chance of transmission can get close to zero. However, the researchers do not yet know where this limit for the coronavirus lies. Since the vaccines don’t provide 100% protection against infection, the Centers for Disease Control and Prevention recommend that people continue to wear masks and social distancing after they have been vaccinated.
In the past few months, new variants of the coronavirus have emerged, and recent studies show that vaccines against certain, such as: the B1351 variant first identified in South Africa.
Every time SARS-CoV-2 replicates, it receives new mutations. In the past few months, researchers have found new variants more infectious – which means a person needs to breathe fewer viruses to become infected – and other variants that are transferable – which means that they increase the amount of virus a person gives off. And researchers have also found at least one new variant that appears to be better able to bypass the immune systemaccording to early data.
How does this relate to vaccines and transmission?
Vaccines are still available for the South African variant more than 85% protection of Serious Illness with COVID – 19. But if you count mild and moderate cases, they only give an approximate at best 50% -60% protection. This means that at least 40% of people vaccinated still have a strong enough infection – and enough virus in their body – to cause at least moderate disease.
When people who have been vaccinated have more virus in their body and less of that virus is required to infect another person, there is a higher chance that a person who has been vaccinated can transmit these new strains of the coronavirus.
If all goes well, vaccines will very soon lower the rate of serious illnesses and deaths around the world. Of course, any vaccine that reduces the severity of the disease will also decrease the total amount of virus shed at the population level. However, with the emergence of new variants, vaccinated people still have the potential to shed the coronavirus and pass it on to other vaccinated or other people. This means that it will likely take time much longer for vaccines to reduce transmission and for populations to achieve herd immunity as if these new variants had never appeared. Exactly how long this will take is a balance between the effectiveness of vaccines against emerging strains and the transmissibility and infectivity of these new strains.