[ad_1]
Nine vaccines have been shown to be effective in protecting people against developing symptoms of Covid-19, the disease that can result from infection with the SARS-CoV-2 virus. However, it is not yet clear to what extent the inoculations prevent people from getting an asymptomatic infection or passing the virus on to others. Preliminary signs suggest that they are doing at least some of both.
Live updates: coronavirus pandemic
1. Why is this important?
Although getting the vaccine gives people considerable insurance against Covid disease, which is sometimes fatal, there is so far no guarantee that they will not be silently infected with SARS-CoV-2 and will not. will not transmit, which could make people potentially nauseating who are not immune. . Those who are infected but never develop symptoms are responsible for 24% of transmission, according to one study.
The more SARS-CoV-2 circulates, the more opportunity the virus has to mutate in ways that improve its ability to spread, sicken and kill people, and evade the immunity provided by existing vaccines or a previous infection. Already, variants of the virus have appeared that seem more dangerous. Additionally, the use of vaccination to achieve so-called collective immunity, when an entire community is protected while not everyone has been vaccinated, requires vaccines that prevent transmission.
2. Don’t vaccines stop infection and therefore transmission?
Some do and some don’t. The gold standard in vaccinology is to stop infection as well as disease – by providing what is called sterilizing immunity. But this is not always realized. The measles vaccine, for example, provides it; that of hepatitis B is not.
Coronavirus pandemic: full coverage
3. Do Covid vaccines need to prevent infection to stop transmission?
Not necessarily. Since a vaccine prevents infection, it also prevents direct transmission. But he can do the latter without doing the former. Since SARS-CoV-2 is spread through respiratory particles in the throat and nose of an infected person, a vaccine that reduces the duration of infection, the amount of virus in the airways (the viral load ) or how often an infected person coughs may decrease the likelihood of it being passed to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
Vaccine testing trials were not designed to answer these questions first. Rather, they were designed to initially determine the most pressing question of whether vaccines would keep people from getting sick and overwhelming medical systems. To explore this question, the researchers typically gave a group of volunteers the experimental vaccine and another group of equal size a placebo. Once the total number of volunteers with confirmed Covid symptoms in the trial reached a predefined level, investigators compared the number in each group to determine whether those who received the vaccine fared much better than those who received the vaccine. had received the placebo. For vaccines that worked, vaccine groups had between 50% and 95% fewer illnesses, numbers known as vaccine effectiveness rates.
5. Why not also check volunteers for asymptomatic infections?
It’s a more complicated endeavor since the only way to find out about asymptomatic infections is to regularly test volunteers, who can number in the tens of thousands in an efficacy trial. Yet about two dozen studies looking at vaccines proven to prevent disease do just that.
6. What did they find?
The results to date are preliminary. The most complete data published relates to the vaccine manufactured by AstraZeneca Plc. In a study in the UK, volunteers are checked for SARS-CoV-2 infections using weekly self-administered nose and throat swabs. According to the results as of Dec. 7, after a single dose, the group that received the vaccine had 67% fewer positive swabs than the placebo group, suggesting that the vaccine reduced infections as well as disease. Previously, Moderna Inc. reported similar results from people who received a single dose of its vaccine in November.
7. What other evidence do we have?
Data from Israel, which has inoculated a higher percentage of its population than any other country, provides clues that the vaccine used there, from Pfizer Inc. and BioNTech SE, may reduce transmission even if it does not protect. not against infection. After more than 75% of people aged 60 or older received a dose of the vaccine and only 25% of those aged 40 to 60, researchers from Israel’s largest coronavirus testing lab looked at their 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 swabs. The researchers estimated that the vaccination reduced the viral load by 1.6 to 20 times in those infected despite the vaccine. Another study in Israel, following people who were infected after inoculation, found that the vaccine lowered their viral load by four. Additionally, a study of Moderna’s Covid vaccine in monkeys suggested that it would reduce or even completely prevent transmission of the virus.
8. When will we know more?
As vaccination becomes more widespread, researchers should be able to discern the effect on infection and transmission patterns, although it may be difficult to distinguish the impact of vaccinations from that of measures such as lock and mask warrants. Completion of vaccine trials to detect asymptomatic infections will provide additional information. Two trials are expected to end in April. However, it is a vaccine from Chinese company Sinovac Biotech Ltd., which has a reported efficacy rate as low as 50% against symptomatic disease. The other is testing the shot from the Russian research institute Gamaleya, which had a 92% efficacy rate against symptoms in clinical trials, but it’s a small study. September should mark the end of many trials of highly effective vaccines. The results of the injections that have been shown to be the most effective in preventing the disease (95%), from Moderna and Pfizer-BioNTech, are not expected until October 2022 and January 2023, respectively.
Live updates: coronavirus pandemic
1. Why is this important?
Although getting the vaccine gives people considerable insurance against Covid disease, which is sometimes fatal, there is so far no guarantee that they will not be silently infected with SARS-CoV-2 and will not. will not transmit, which could make people potentially nauseating who are not immune. . Those who are infected but never develop symptoms are responsible for 24% of transmission, according to one study.
The more SARS-CoV-2 circulates, the more opportunity the virus has to mutate in ways that improve its ability to spread, sicken and kill people, and evade the immunity provided by existing vaccines or a previous infection. Already, variants of the virus have appeared that seem more dangerous. Additionally, the use of vaccination to achieve so-called collective immunity, when an entire community is protected while not everyone has been vaccinated, requires vaccines that prevent transmission.
2. Don’t vaccines stop infection and therefore transmission?
Some do and some don’t. The gold standard in vaccinology is to stop infection as well as disease – by providing what is called sterilizing immunity. But this is not always realized. The measles vaccine, for example, provides it; that of hepatitis B is not.
Coronavirus pandemic: full coverage
3. Do Covid vaccines need to prevent infection to stop transmission?
Not necessarily. Since a vaccine prevents infection, it also prevents direct transmission. But he can do the latter without doing the former. Since SARS-CoV-2 is spread through respiratory particles in the throat and nose of an infected person, a vaccine that reduces the duration of infection, the amount of virus in the airways (the viral load ) or how often an infected person coughs may decrease the likelihood of it being passed to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
Vaccine testing trials were not designed to answer these questions first. Rather, they were designed to initially determine the most pressing question of whether vaccines would keep people from getting sick and overwhelming medical systems. To explore this question, the researchers typically gave a group of volunteers the experimental vaccine and another group of equal size a placebo. Once the total number of volunteers with confirmed Covid symptoms in the trial reached a predefined level, investigators compared the number in each group to determine whether those who received the vaccine fared much better than those who received the vaccine. had received the placebo. For vaccines that worked, vaccine groups had between 50% and 95% fewer illnesses, numbers known as vaccine effectiveness rates.
5. Why not also check volunteers for asymptomatic infections?
It’s a more complicated endeavor since the only way to find out about asymptomatic infections is to regularly test volunteers, who can number in the tens of thousands in an efficacy trial. Yet about two dozen studies looking at vaccines proven to prevent disease do just that.
6. What did they find?
The results to date are preliminary. The most complete data published relates to the vaccine manufactured by AstraZeneca Plc. In a study in the UK, volunteers are checked for SARS-CoV-2 infections using weekly self-administered nose and throat swabs. According to the results as of Dec. 7, after a single dose, the group that received the vaccine had 67% fewer positive swabs than the placebo group, suggesting that the vaccine reduced infections as well as disease. Previously, Moderna Inc. reported similar results from people who received a single dose of its vaccine in November.
7. What other evidence do we have?
Data from Israel, which has inoculated a higher percentage of its population than any other country, provides clues that the vaccine used there, from Pfizer Inc. and BioNTech SE, may reduce transmission even if it does not protect. not against infection. After more than 75% of people aged 60 or older received a dose of the vaccine and only 25% of those aged 40 to 60, researchers from Israel’s largest coronavirus testing lab looked at their 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 swabs. The researchers estimated that the vaccination reduced the viral load by 1.6 to 20 times in those infected despite the vaccine. Another study in Israel, following people who were infected after inoculation, found that the vaccine lowered their viral load by four. Additionally, a study of Moderna’s Covid vaccine in monkeys suggested that it would reduce or even completely prevent transmission of the virus.
8. When will we know more?
As vaccination becomes more widespread, researchers should be able to discern the effect on infection and transmission patterns, although it may be difficult to distinguish the impact of vaccinations from that of measures such as lock and mask warrants. Completion of vaccine trials to detect asymptomatic infections will provide additional information. Two trials are expected to end in April. However, it is a vaccine from Chinese company Sinovac Biotech Ltd., which has a reported efficacy rate as low as 50% against symptomatic disease. The other is testing the shot from the Russian research institute Gamaleya, which had a 92% efficacy rate against symptoms in clinical trials, but it’s a small study. September should mark the end of many trials of highly effective vaccines. The results of the injections that have been shown to be the most effective in preventing the disease (95%), from Moderna and Pfizer-BioNTech, are not expected until October 2022 and January 2023, respectively.
[ad_2]
Source link