What do the efficacy results of Pfizer's clinical trial mean?
What do the efficacy results of Pfizer's clinical trial mean?
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On November 18th, 2020, Pfizer announced that its experimental COVID-19 vaccine (BNT162b2) prevented infection in 95% of overall participants who received the drug company’s late-stage clinical trial dose. In adults over 65 years of age, the vaccine was effective in over 94% of volunteers. These early results exceeded the minimum United States Food and Drug Administration (U.S. FDA) target of 50% efficacy—but it is important to reiterate that no vaccine is ever 100% effective. It is impossible to know how well a vaccine actually works until it is deployed in the real world and given to large populations, not just volunteer participants in a trial. While the current data is promising, it has yet to be evaluated by the U.S. FDA, and more information is needed before Pfizer can pursue approval for the vaccine. The company has concluded its phase III trial but will continue to monitor patients for any adverse reactions or events. Additionally, to ensure that there are not major safety concerns, the U.S. FDA is requiring manufacturers to provide at least two months of follow-up data for at least half of the volunteer participants. Most serious side effects from vaccines occur within about six weeks after the vaccine is given. In vaccine clinical trials, any observed impacts of the vaccine on volunteer participants are eventually considered side effects with more serious side effects causing the trials to pause or stop completely. No safety concerns about these potential side effects have been reported so far. Pfizer recently stated that the only side effects that occurred in more than 2% of participants was fatigue at 3.8% and headache at 2.0%. Because the news about this vaccine is still early, there is still a lot we don't know. Remaining questions include when the vaccine might be available for everyone, if it will work in children younger than 12 (as they have been excluded from the early trials), if it will stop the virus from spreading in people who are infected but don't have any symptoms (asymptomatic), if it will prevent people from developing severe cases, and how long the vaccine might offer protection from the the virus. This vaccine requires an initial injection followed by a secondary shot called a “booster” to achieve its full level of protection. The vaccine was found to be effective against COVID-19 beginning 28 days after the first dose. The clinical trial included more than 43,000 volunteer participants, many of whom already received two doses of the vaccine. In the interim analysis, there were 94 cases of COVID-19 in trial participants, and the study continued until there have been 164 cases of COVID-19 among study volunteers. It is important to note that these study results may not play out the same under “real life” circumstances because of differences in health status, weight, age, and other factors across communities. While Pfizer has reported that 42% of participants are from “diverse backgrounds,” the study population may not reflect the diversity of our global populations and communities despite the vaccine being effective across age, gender, race and ethnicity demographics in the trials.
On November 18th, 2020, Pfizer announced that its experimental COVID-19 vaccine (BNT162b2) prevented infection in 95% of overall participants who received the drug company’s late-stage clinical trial dose. In adults over 65 years of age, the vaccine was effective in over 94% of volunteers. These early results exceeded the minimum United States Food and Drug Administration (U.S. FDA) target of 50% efficacy—but it is important to reiterate that no vaccine is ever 100% effective. It is impossible to know how well a vaccine actually works until it is deployed in the real world and given to large populations, not just volunteer participants in a trial. While the current data is promising, it has yet to be evaluated by the U.S. FDA, and more information is needed before Pfizer can pursue approval for the vaccine. The company has concluded its phase III trial but will continue to monitor patients for any adverse reactions or events. Additionally, to ensure that there are not major safety concerns, the U.S. FDA is requiring manufacturers to provide at least two months of follow-up data for at least half of the volunteer participants. Most serious side effects from vaccines occur within about six weeks after the vaccine is given. In vaccine clinical trials, any observed impacts of the vaccine on volunteer participants are eventually considered side effects with more serious side effects causing the trials to pause or stop completely. No safety concerns about these potential side effects have been reported so far. Pfizer recently stated that the only side effects that occurred in more than 2% of participants was fatigue at 3.8% and headache at 2.0%. Because the news about this vaccine is still early, there is still a lot we don't know. Remaining questions include when the vaccine might be available for everyone, if it will work in children younger than 12 (as they have been excluded from the early trials), if it will stop the virus from spreading in people who are infected but don't have any symptoms (asymptomatic), if it will prevent people from developing severe cases, and how long the vaccine might offer protection from the the virus. This vaccine requires an initial injection followed by a secondary shot called a “booster” to achieve its full level of protection. The vaccine was found to be effective against COVID-19 beginning 28 days after the first dose. The clinical trial included more than 43,000 volunteer participants, many of whom already received two doses of the vaccine. In the interim analysis, there were 94 cases of COVID-19 in trial participants, and the study continued until there have been 164 cases of COVID-19 among study volunteers. It is important to note that these study results may not play out the same under “real life” circumstances because of differences in health status, weight, age, and other factors across communities. While Pfizer has reported that 42% of participants are from “diverse backgrounds,” the study population may not reflect the diversity of our global populations and communities despite the vaccine being effective across age, gender, race and ethnicity demographics in the trials.
Publication
What our experts say
On November 18th, 2020, Pfizer announced that its experimental COVID-19 vaccine (BNT162b2) prevented infection in 95% of overall participants who received the drug company’s late-stage clinical trial dose. In adults over 65 years of age, the vaccine was effective in over 94% of volunteers. These early results exceeded the minimum United States Food and Drug Administration (U.S. FDA) target of 50% efficacy—but it is important to reiterate that no vaccine is ever 100% effective. It is impossible to know how well a vaccine actually works until it is deployed in the real world and given to large populations, not just volunteer participants in a trial.
While the current data is promising, it has yet to be evaluated by the U.S. FDA, and more information is needed before Pfizer can pursue approval for the vaccine. The company has concluded its phase III trial but will continue to monitor patients for any adverse reactions or events. Additionally, to ensure that there are not major safety concerns, the U.S. FDA is requiring manufacturers to provide at least two months of follow-up data for at least half of the volunteer participants. Most serious side effects from vaccines occur within about six weeks after the vaccine is given. In vaccine clinical trials, any observed impacts of the vaccine on volunteer participants are eventually considered side effects with more serious side effects causing the trials to pause or stop completely. No safety concerns about these potential side effects have been reported so far. Pfizer recently stated that the only side effects that occurred in more than 2% of participants was fatigue at 3.8% and headache at 2.0%.
Because the news about this vaccine is still early, there is still a lot we don't know. Remaining questions include when the vaccine might be available for everyone, if it will work in children younger than 12 (as they have been excluded from the early trials), if it will stop the virus from spreading in people who are infected but don't have any symptoms (asymptomatic), if it will prevent people from developing severe cases, and how long the vaccine might offer protection from the the virus.
This vaccine requires an initial injection followed by a secondary shot called a “booster” to achieve its full level of protection. The vaccine was found to be effective against COVID-19 beginning 28 days after the first dose. The clinical trial included more than 43,000 volunteer participants, many of whom already received two doses of the vaccine. In the interim analysis, there were 94 cases of COVID-19 in trial participants, and the study continued until there have been 164 cases of COVID-19 among study volunteers.
It is important to note that these study results may not play out the same under “real life” circumstances because of differences in health status, weight, age, and other factors across communities. While Pfizer has reported that 42% of participants are from “diverse backgrounds,” the study population may not reflect the diversity of our global populations and communities despite the vaccine being effective across age, gender, race and ethnicity demographics in the trials.
On November 18th, 2020, Pfizer announced that its experimental COVID-19 vaccine (BNT162b2) prevented infection in 95% of overall participants who received the drug company’s late-stage clinical trial dose. In adults over 65 years of age, the vaccine was effective in over 94% of volunteers. These early results exceeded the minimum United States Food and Drug Administration (U.S. FDA) target of 50% efficacy—but it is important to reiterate that no vaccine is ever 100% effective. It is impossible to know how well a vaccine actually works until it is deployed in the real world and given to large populations, not just volunteer participants in a trial.
While the current data is promising, it has yet to be evaluated by the U.S. FDA, and more information is needed before Pfizer can pursue approval for the vaccine. The company has concluded its phase III trial but will continue to monitor patients for any adverse reactions or events. Additionally, to ensure that there are not major safety concerns, the U.S. FDA is requiring manufacturers to provide at least two months of follow-up data for at least half of the volunteer participants. Most serious side effects from vaccines occur within about six weeks after the vaccine is given. In vaccine clinical trials, any observed impacts of the vaccine on volunteer participants are eventually considered side effects with more serious side effects causing the trials to pause or stop completely. No safety concerns about these potential side effects have been reported so far. Pfizer recently stated that the only side effects that occurred in more than 2% of participants was fatigue at 3.8% and headache at 2.0%.
Because the news about this vaccine is still early, there is still a lot we don't know. Remaining questions include when the vaccine might be available for everyone, if it will work in children younger than 12 (as they have been excluded from the early trials), if it will stop the virus from spreading in people who are infected but don't have any symptoms (asymptomatic), if it will prevent people from developing severe cases, and how long the vaccine might offer protection from the the virus.
This vaccine requires an initial injection followed by a secondary shot called a “booster” to achieve its full level of protection. The vaccine was found to be effective against COVID-19 beginning 28 days after the first dose. The clinical trial included more than 43,000 volunteer participants, many of whom already received two doses of the vaccine. In the interim analysis, there were 94 cases of COVID-19 in trial participants, and the study continued until there have been 164 cases of COVID-19 among study volunteers.
It is important to note that these study results may not play out the same under “real life” circumstances because of differences in health status, weight, age, and other factors across communities. While Pfizer has reported that 42% of participants are from “diverse backgrounds,” the study population may not reflect the diversity of our global populations and communities despite the vaccine being effective across age, gender, race and ethnicity demographics in the trials.
Context and background
Vaccine efficacy and vaccine effectiveness are similar terms, but the differences between them are important to note when we are learning about new vaccines to prevent COVID-19. The term “vaccine efficacy” is used to measure how well a vaccine works to prevent a particular disease (in this case, COVID-19) in controlled, research environments. “Vaccine effectiveness” studies examine how well a vaccine prevents a particular disease in the “real world” community environment where people are doing things like going to the grocery store, work, and school.
In the recently published interim report from Pfizer’s experimental COVID-19 vaccine trial, the vaccine efficacy was reported at 95%, which means that people who were vaccinated in the study are much less likely to contract COVID-19 than the control group, who were not vaccinated with the experimental drug. Using an example of 100 trial participants in a given trial of a vaccine with 90% efficacy, 90 patients would not contract the disease and 10 would contract COVID-19. In Pfizer's clinical trials, there were 10 severe cases of COVID-19. Nine of the cases were in the in the placebo group and one in the vaccinated group.
If this vaccine receives U.S. Food and Drug Administration (U.S. FDA) approval and is distributed to large populations around the world, scientists will then be able to calculate vaccine effectiveness in real-world settings. The U.S. FDA has set the minimum efficacy requirement at 50% for potential COVID-19 vaccines, though many hope that the vaccines currently in development will exceed this target. Real world vaccine effectiveness is a much more reliable and accurate term for telling us how helpful a vaccine is at preventing disease in daily life, not just in a controlled, research setting.
Like the flu vaccine, an effective COVID-19 vaccine may also help to reduce the severity of disease for those who do become infected, which may keep patients out of the hospital or out of intensive care. The goal of vaccines is to protect populations from diseases, and this vaccine is no different. Whether or not it will be successful depends on its study results (which are evaluated by the U.S. FDA), distribution among different people in different settings, how many people agree to receive the vaccine, how long its protection lasts, and many other elements that vary by each country.
Pfizer aims to produce up to 50 million vaccine doses across the world in 2020 and up to 1.3 billion doses by the end of 2021.
Vaccine efficacy and vaccine effectiveness are similar terms, but the differences between them are important to note when we are learning about new vaccines to prevent COVID-19. The term “vaccine efficacy” is used to measure how well a vaccine works to prevent a particular disease (in this case, COVID-19) in controlled, research environments. “Vaccine effectiveness” studies examine how well a vaccine prevents a particular disease in the “real world” community environment where people are doing things like going to the grocery store, work, and school.
In the recently published interim report from Pfizer’s experimental COVID-19 vaccine trial, the vaccine efficacy was reported at 95%, which means that people who were vaccinated in the study are much less likely to contract COVID-19 than the control group, who were not vaccinated with the experimental drug. Using an example of 100 trial participants in a given trial of a vaccine with 90% efficacy, 90 patients would not contract the disease and 10 would contract COVID-19. In Pfizer's clinical trials, there were 10 severe cases of COVID-19. Nine of the cases were in the in the placebo group and one in the vaccinated group.
If this vaccine receives U.S. Food and Drug Administration (U.S. FDA) approval and is distributed to large populations around the world, scientists will then be able to calculate vaccine effectiveness in real-world settings. The U.S. FDA has set the minimum efficacy requirement at 50% for potential COVID-19 vaccines, though many hope that the vaccines currently in development will exceed this target. Real world vaccine effectiveness is a much more reliable and accurate term for telling us how helpful a vaccine is at preventing disease in daily life, not just in a controlled, research setting.
Like the flu vaccine, an effective COVID-19 vaccine may also help to reduce the severity of disease for those who do become infected, which may keep patients out of the hospital or out of intensive care. The goal of vaccines is to protect populations from diseases, and this vaccine is no different. Whether or not it will be successful depends on its study results (which are evaluated by the U.S. FDA), distribution among different people in different settings, how many people agree to receive the vaccine, how long its protection lasts, and many other elements that vary by each country.
Pfizer aims to produce up to 50 million vaccine doses across the world in 2020 and up to 1.3 billion doses by the end of 2021.
Resources
- Vaccine efficacy or vaccine effectiveness (CDC)
- How Flu Vaccine Effectiveness and Efficacy are Measured (CDC)
- Overview of Vaccine Efficacy and Vaccine Effectiveness (WHO)
- What does COVID-19 vaccine efficacy mean? (Science News)
- What defines an efficacious COVID-19 vaccine? A review of the challenges assessing the clinical efficacy of vaccines against SARS-CoV-2 (The Lancet)
- A COVID-19 Vaccine May Be Only 50% Effective. Is That Good Enough? (NPR)
- Pfizer’s Covid Vaccine: 11 Things You Need to Know (New York Times)
- Pfizer and BioNTech Conclude Phase 3 Study of COVID-19 Vaccine Candidate, Meeting All Primary Efficacy Endpoints (Pfizer)
- Vaccine efficacy or vaccine effectiveness (CDC)
- How Flu Vaccine Effectiveness and Efficacy are Measured (CDC)
- Overview of Vaccine Efficacy and Vaccine Effectiveness (WHO)
- What does COVID-19 vaccine efficacy mean? (Science News)
- What defines an efficacious COVID-19 vaccine? A review of the challenges assessing the clinical efficacy of vaccines against SARS-CoV-2 (The Lancet)
- A COVID-19 Vaccine May Be Only 50% Effective. Is That Good Enough? (NPR)
- Pfizer’s Covid Vaccine: 11 Things You Need to Know (New York Times)
- Pfizer and BioNTech Conclude Phase 3 Study of COVID-19 Vaccine Candidate, Meeting All Primary Efficacy Endpoints (Pfizer)
