Nine vaccines have been shown to be effective in protecting people against the symptoms of Covid-19, the disease that can result from infection with the SARS-CoV-2 virus. However, it is not yet known to what extent inoculations prevent people from having an asymptomatic infection or transmitting the virus to other people. Preliminary signs suggest they are doing at least some of the two things.
Live updates: coronavirus pandemic
1. Why is it important?
While vaccination provides people with considerable insurance against Covid disease, which is sometimes fatal, so far there is no guarantee that they will not be silently infected with SARS-CoV-2 and transmitted, potentially sick people. which is not immune. . According to one study, people who are infected but never show symptoms are responsible for 24% of the transmission.
The more SARS-CoV-2 circulates, the more chances the virus has to mutate in a way that improves its ability to spread, disease, and kill people, and evades the immunity provided by existing vaccines or a past infection. Variants of the virus have already appeared that appear to be more dangerous. In addition, the use of vaccination to achieve so-called herd immunity, when an entire community is protected even though not everyone has been immunized, requires vaccines that prevent transmission.
2. Do vaccines not stop infection and therefore transmission?
Some yes and some no. The gold standard in vaccinology is to stop infection and disease, providing so-called sterilizing immunity. But it is not always achieved. The measles vaccine, for example, provides it; that of hepatitis B no.
Coronavirus pandemic: full coverage
3. Should Covid vaccines prevent infection to stop transmission?
Not necessarily. To the extent that a vaccine prevents infection, it also prevents forward transmission. But you can do the second without doing the first. Since SARS-CoV-2 is spread by respiratory particles from the throat and nose of an infected person, a vaccine that reduces the duration of infection, the amount of virus in the airways (viral load) or the frequency with which an infected person coughs decrease the likelihood of it being transmitted to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
The trials that tested the vaccines were not created to answer these questions first. Rather, they were designed to initially determine the most pressing issue of whether vaccines would prevent people from getting sick and overwhelming medical systems. To explore this issue, researchers used to give one group of volunteers the experimental vaccine and another group of equal size a placebo. After the total number of volunteers with Covid symptoms confirmed in the trial reached a predetermined level, the researchers compared the number of each group to determine whether those who received the vaccine had a significantly better outcome than those who received the vaccine. receive the placebo. For inoculations that have worked, vaccine groups have had between 50% and 95% fewer cases of disease, figures known as vaccine efficacy rates.
5. Why not check for asymptomatic infections in volunteers?
This is a more complicated undertaking, as the only way to know about asymptomatic infections is to regularly test volunteers, who can be in the tens of thousands in an efficacy trial. However, approximately two dozen studies related to vaccines tested to prevent disease do so exactly.
6. What have they found?
The results so far are preliminary. The most extensive data published refers to the vaccine made by AstraZeneca Plc. In a study in the UK, it is checked for SARS-CoV-2 infections in volunteers using weekly self-administered nose and throat swabs. According to the December 7 results, after a single dose, the group that received the vaccine had 67% fewer positive buffers than the placebo group, suggesting that the vaccine will reduce infections and disease. Before, Modern Inc. reported similar results from people who had received a single dose of their vaccine in November.
7. What other tests do we have?
Data from Israel, which has inoculated a higher percentage of its population than any other country, provides clues than the vaccine used there, from Pfizer Inc. and BioNTech SE, can reduce transmission even if it does not protect against infection. After more than 75% of people aged 60 and over had received a dose of vaccine and only 25% of people aged 40 to 60, researchers at Israel’s largest coronavirus testing laboratory examined your data. For those who tested positive for SARS-CoV-2, there was a noticeable difference between the two age groups in the average amount of virus found in the test buffers. The researchers estimated that vaccination reduces viral load by 1.6 to 20 times in infected individuals despite the shot. Another study in Israel, after people who became infected after inoculation, found that the vaccine reduced their viral load by four. In addition, a study of Modov’s Covid vaccine in monkeys suggested that it will reduce, if not completely prevent, subsequent transmission of the virus.
8. When will we know more?
As vaccination spreads, researchers should be able to discern the effect on infection and transmission patterns, although it may be difficult to distinguish the impact of inoculations from that of measures such as blockages and mandates of masks. Completion of vaccine trials to detect asymptomatic infections will provide additional information. Two tests are expected to be completed in April. However, one of the vaccines from China’s Sinovac Biotech Ltd., which has an effectiveness rate as low as 50% against symptomatic diseases. Other tests test the shooting of the Gamaleya Research Institute in Russia, whose effectiveness against symptoms was 92% in clinical trials, but it is a small study. The month of September should end with considerable trials of highly effective vaccines. The results of the dams that have proven to be most effective in preventing disease (95%), from Moderna and Pfizer-BioNTech, are not expected until October 2022 and January 2023, respectively.
Live updates: coronavirus pandemic
1. Why is it important?
While vaccination provides people with considerable insurance against Covid disease, which is sometimes fatal, so far there is no guarantee that they will not be silently infected with SARS-CoV-2 and transmitted, potentially sick people. which is not immune. . According to one study, people who are infected but never show symptoms are responsible for 24% of the transmission.
The more SARS-CoV-2 circulates, the more chances the virus has to mutate in a way that improves its ability to spread, disease, and kill people, and evades the immunity provided by existing vaccines or a past infection. Variants of the virus have already appeared that appear to be more dangerous. In addition, the use of vaccination to achieve so-called herd immunity, when an entire community is protected even though not everyone has been immunized, requires vaccines that prevent transmission.
2. Do vaccines not stop infection and therefore transmission?
Some yes and some no. The gold standard in vaccinology is to stop infection and disease, providing so-called sterilizing immunity. But it is not always achieved. The measles vaccine, for example, provides it; that of hepatitis B no.
Coronavirus pandemic: full coverage
3. Should Covid vaccines prevent infection to stop transmission?
Not necessarily. To the extent that a vaccine prevents infection, it also prevents forward transmission. But you can do the second without doing the first. Since SARS-CoV-2 is spread by respiratory particles from the throat and nose of an infected person, a vaccine that reduces the duration of infection, the amount of virus in the airways (viral load) or the frequency with which an infected person coughs decrease the likelihood of it being transmitted to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
The trials that tested the vaccines were not created to answer these questions first. Rather, they were designed to initially determine the most pressing issue of whether vaccines would prevent people from getting sick and overwhelming medical systems. To explore this issue, researchers used to give one group of volunteers the experimental vaccine and another group of equal size a placebo. After the total number of volunteers with Covid symptoms confirmed in the trial reached a predetermined level, the researchers compared the number of each group to determine whether those who received the vaccine had a significantly better outcome than those who received the vaccine. receive the placebo. For inoculations that have worked, vaccine groups have had between 50% and 95% fewer cases of disease, figures known as vaccine efficacy rates.
5. Why not check for asymptomatic infections in volunteers?
This is a more complicated undertaking, as the only way to know about asymptomatic infections is to regularly test volunteers, who can be in the tens of thousands in an efficacy trial. However, approximately two dozen studies related to vaccines tested to prevent disease do so exactly.
6. What have they found?
The results so far are preliminary. The most extensive data published refers to the vaccine made by AstraZeneca Plc. In a study in the UK, it is checked for SARS-CoV-2 infections in volunteers using weekly self-administered nose and throat swabs. According to the December 7 results, after a single dose, the group that received the vaccine had 67% fewer positive buffers than the placebo group, suggesting that the vaccine will reduce infections and disease. Before, Modern Inc. reported similar results from people who had received a single dose of their vaccine in November.
7. What other tests do we have?
Data from Israel, which has inoculated a higher percentage of its population than any other country, provides clues than the vaccine used there, from Pfizer Inc. and BioNTech SE, can reduce transmission even if it does not protect against infection. After more than 75% of people aged 60 and over had received a dose of vaccine and only 25% of people aged 40 to 60, researchers at Israel’s largest coronavirus testing laboratory examined your data. For those who tested positive for SARS-CoV-2, there was a noticeable difference between the two age groups in the average amount of virus found in the test buffers. The researchers estimated that vaccination reduces viral load by 1.6 to 20 times in infected individuals despite the shot. Another study in Israel, after people who became infected after inoculation, found that the vaccine reduced their viral load by four. In addition, a study of Modov’s Covid vaccine in monkeys suggested that it will reduce, if not completely prevent, subsequent transmission of the virus.
8. When will we know more?
As vaccination spreads, researchers should be able to discern the effect on infection and transmission patterns, although it may be difficult to distinguish the impact of inoculations from that of measures such as blockages and mandates of masks. Completion of vaccine trials to detect asymptomatic infections will provide additional information. Two tests are expected to be completed in April. However, one of the vaccines from China’s Sinovac Biotech Ltd., which has an effectiveness rate as low as 50% against symptomatic diseases. Other tests test the shooting of the Gamaleya Research Institute in Russia, whose effectiveness against symptoms was 92% in clinical trials, but it is a small study. The month of September should end with considerable trials of highly effective vaccines. The results of the dams that have proven to be most effective in preventing disease (95%), from Moderna and Pfizer-BioNTech, are not expected until October 2022 and January 2023, respectively.