Nine vaccines have been shown to be effective in protecting people from developing symptoms of Covid-19, the disease that can result from infection with the SARS-CoV-2 virus. However, it is not yet known how well the vaccinations prevent people from getting an asymptomatic infection or passing the virus on to others. Preliminary signs suggest they do at least some of both.
Live Updates: Coronavirus Pandemic
1. Why is this important?
While vaccination provides people with significant insurance against getting sick with Covid, which is sometimes fatal, so far it is no guarantee that they will not become tacitly infected with SARS-CoV-2 and pass it on, potentially pathogenic people who are not immune. . Those who are infected but never develop symptoms are responsible for 24% of transmission, one study estimates.
The more SARS-CoV-2 circulates, the more likely the virus is to mutate in ways that increase its ability to spread, sicken and kill people, and bypass the immunity of existing vaccines or previous infection. Variants of the virus have already surfaced that seem more dangerous. Also, the use of vaccination to achieve so-called herd immunity, when an entire community is protected even though not everyone is immunized, requires vaccines that prevent transmission.
2. Do vaccines not stop the infection and therefore the transmission?
Some do and some don’t. The gold standard in vaccinology is to stop both infection and disease – providing so-called sterilizing immunity. But it is not always achieved. For example, the measles vaccine offers it; those for hepatitis B are not.
Coronavirus Pandemic: Full Coverage
3. Should Covid vaccines prevent infection to stop transmission?
Not necessary. To the extent that a vaccine prevents infection, it also prevents forward transmission. But it can do the latter without doing the former. Since SARS-CoV-2 spreads through respiratory particles from the throat and nose of an infected person, a vaccine is used to measure the duration of the infection, the amount of virus in the airways (the viral load), or how often an infected person coughs. reduce the chance of it being passed on to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
The trials with the vaccines were not intended to answer those questions first. Rather, they were intended to initially determine the more pressing issue of whether vaccines would prevent people from getting sick and overwhelm medical systems. To investigate that question, researchers typically gave one group of volunteers the experimental vaccine and another group of equal size a placebo. After the total number of volunteers with confirmed Covid symptoms in the study reached a predetermined level, the researchers compared the number in each group to determine whether those who received the vaccine fared significantly better than those who received the placebo. As for the vaccinations that have worked, the vaccine groups have had anywhere from 50% to 95% fewer cases of disease, numbers called the vaccine efficacy rates.
5. Why don’t volunteers also check for asymptomatic infections?
This is a more complicated endeavor, since the only way to know about asymptomatic infections is to regularly test volunteers, who can number up to tens of thousands in an efficacy trial. Yet about two dozen studies with the vaccines proven to prevent disease do just that.
6. What did they find?
The results so far are preliminary. The most comprehensive data released relates to the vaccine made by AstraZeneca Plc. In a study in the UK, volunteers are monitored for SARS-CoV-2 infections with weekly self-administered nose and throat swabs. According to the results on Dec. 7, the group that received the vaccine had 67% fewer positive smears after a single dose than the placebo group, suggesting that the vaccine reduces infections as well as disease. Previously, Moderna Inc. similar results from people who had received a single dose of the vaccine from November onwards.
7. What other proof do we have?
Data from Israel, which has vaccinated a higher percentage of its population than any other country, indicates that the vaccine used there is 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 or older received one dose of vaccination and only 25% of those between the ages of 40 and 60, researchers at Israel’s largest coronavirus testing laboratory looked at their data. For those who tested positive for SARS-CoV-2, there was a notable difference between the two age groups in the mean amount of virus found in test sticks. The researchers estimate that vaccination reduces the viral load 1.6 to 20 times in individuals who become infected despite the shot. Another study in Israel, which followed people infected after inoculation, found that the vaccine quadrupled their viral load. Also, a study of Moderna’s Covid vaccine in monkeys suggested that it would reduce, if not completely prevent, the further 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 can be difficult to distinguish the impact of vaccinations from measures such as lockdowns and mask mandates. The completion of the vaccine trials that test for asymptomatic infections will provide additional information. Two trials are expected to end in April. However, one is from a vaccine from China’s Sinovac Biotech Ltd., which has an efficacy rate of only 50% against symptomatic diseases. The other tests the shot from Russia’s Gamaleya Research Institute, whose efficacy against symptoms was 92% in clinical trials, but it’s a small study. September should mark the completion of extensive trials of highly effective vaccines. Results from the shots that have proven 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 this important?
While vaccination provides people with significant insurance against getting sick with Covid, which is sometimes fatal, so far it is no guarantee that they will not become tacitly infected with SARS-CoV-2 and pass it on, potentially pathogenic people who are not immune. . Those who are infected but never develop symptoms are responsible for 24% of transmission, one study estimates.
The more SARS-CoV-2 circulates, the more likely the virus is to mutate in ways that increase its ability to spread, sicken and kill people, and bypass the immunity of existing vaccines or previous infection. Variants of the virus have already surfaced that seem more dangerous. Also, the use of vaccination to achieve so-called herd immunity, when an entire community is protected even though not everyone is immunized, requires vaccines that prevent transmission.
2. Do vaccines not stop the infection and therefore the transmission?
Some do and some don’t. The gold standard in vaccinology is to stop both infection and disease – providing so-called sterilizing immunity. But it is not always achieved. For example, the measles vaccine offers it; those for hepatitis B are not.
Coronavirus Pandemic: Full Coverage
3. Should Covid vaccines prevent infection to stop transmission?
Not necessary. To the extent that a vaccine prevents infection, it also prevents forward transmission. But it can do the latter without doing the former. Since SARS-CoV-2 spreads through respiratory particles from the throat and nose of an infected person, a vaccine is used to measure the duration of the infection, the amount of virus in the airways (the viral load), or how often an infected person coughs. reduce the chance of it being passed on to others.
4. Why don’t we know if Covid vaccines prevent infection and transmission?
The trials with the vaccines were not intended to answer those questions first. Rather, they were intended to initially determine the more pressing issue of whether vaccines would prevent people from getting sick and overwhelm medical systems. To investigate that question, researchers typically gave one group of volunteers the experimental vaccine and another group of equal size a placebo. After the total number of volunteers with confirmed Covid symptoms in the study reached a predetermined level, the researchers compared the number in each group to determine whether those who received the vaccine fared significantly better than those who received the placebo. As for the vaccinations that have worked, the vaccine groups have had anywhere from 50% to 95% fewer cases of disease, numbers called the vaccine efficacy rates.
5. Why don’t volunteers also check for asymptomatic infections?
This is a more complicated endeavor, since the only way to know about asymptomatic infections is to regularly test volunteers, who can number up to tens of thousands in an efficacy trial. Yet about two dozen studies with the vaccines proven to prevent disease do just that.
6. What did they find?
The results so far are preliminary. The most comprehensive data released relates to the vaccine made by AstraZeneca Plc. In a study in the UK, volunteers are monitored for SARS-CoV-2 infections with weekly self-administered nose and throat swabs. According to the results on Dec. 7, the group that received the vaccine had 67% fewer positive smears after a single dose than the placebo group, suggesting that the vaccine reduces infections as well as disease. Previously, Moderna Inc. similar results from people who had received a single dose of the vaccine from November onwards.
7. What other proof do we have?
Data from Israel, which has vaccinated a higher percentage of its population than any other country, indicates that the vaccine used there is 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 or older received one dose of vaccination and only 25% of those between the ages of 40 and 60, researchers at Israel’s largest coronavirus testing laboratory looked at their data. For those who tested positive for SARS-CoV-2, there was a notable difference between the two age groups in the mean amount of virus found in test sticks. The researchers estimate that vaccination reduces the viral load 1.6 to 20 times in individuals who become infected despite the shot. Another study in Israel, which followed people infected after inoculation, found that the vaccine quadrupled their viral load. Also, a study of Moderna’s Covid vaccine in monkeys suggested that it would reduce, if not completely prevent, the further 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 can be difficult to distinguish the impact of vaccinations from measures such as lockdowns and mask mandates. The completion of the vaccine trials that test for asymptomatic infections will provide additional information. Two trials are expected to end in April. However, one is from a vaccine from China’s Sinovac Biotech Ltd., which has an efficacy rate of only 50% against symptomatic diseases. The other tests the shot from Russia’s Gamaleya Research Institute, whose efficacy against symptoms was 92% in clinical trials, but it’s a small study. September should mark the completion of extensive trials of highly effective vaccines. Results from the shots that have proven most effective in preventing disease (95%), from Moderna and Pfizer-BioNTech, are not expected until October 2022 and January 2023, respectively.