Key Takeaways

How Effective Is AstraZeneca’s Vaccine?The Oxford researchers report the AstraZeneca vaccine is 76% effective at protecting against primary symptomatic COVID-19 once a person is 22 days out from their first dose. Protection does not fade for 90 days from that first jab. After a second dose is given three months later, vaccine efficacy increases to 82.4%.According to Oxford, the robust efficacy after the initial shot supports the strategies that some nations are using, like spacing out the second dose to 12 weeks, to get as many first doses of the AstraZeneca vaccine to citizens as quickly as possible.

How Effective Is AstraZeneca’s Vaccine?

The Oxford researchers report the AstraZeneca vaccine is 76% effective at protecting against primary symptomatic COVID-19 once a person is 22 days out from their first dose. Protection does not fade for 90 days from that first jab. After a second dose is given three months later, vaccine efficacy increases to 82.4%.According to Oxford, the robust efficacy after the initial shot supports the strategies that some nations are using, like spacing out the second dose to 12 weeks, to get as many first doses of the AstraZeneca vaccine to citizens as quickly as possible.

The Oxford researchers report the AstraZeneca vaccine is 76% effective at protecting against primary symptomatic COVID-19 once a person is 22 days out from their first dose. Protection does not fade for 90 days from that first jab. After a second dose is given three months later, vaccine efficacy increases to 82.4%.

According to Oxford, the robust efficacy after the initial shot supports the strategies that some nations are using, like spacing out the second dose to 12 weeks, to get as many first doses of the AstraZeneca vaccine to citizens as quickly as possible.

An Overview of the AstraZeneca-Oxford COVID-19 Vaccine

The Study

The analysis of the Oxford-AstraZeneca vaccine’s (AZD1222) ongoing trial was published as a preprint (meaning it is still under review) inThe Lancet. One of the study’s most intriguing findings was that the vaccine might have a “substantial effect on transmission.”

Participants in the United Kingdom arm of the study were asked to produce nasal swabs each week. Next, the samples underwent polymerase chain reaction (PCR) testing to detect the presence of SARS-CoV-2 (the virus that causes COVID-19).

Researchers found a 67% reduction in positive swabs among participants who had received their first dose of the vaccine.

“When you have an effective vaccine and it mounts a good immune response [and] a person is exposed to the virus, the strength of the immune response will dictate course of the disease and how fast the virus is cleared from the system.” Jagdish Khubchandani, PhD, professor of public health at New Mexico State University, tells Verywell. “This, in turn, would relate to transmissibility.”

However, after two doses of the vaccine, researchers found only a 49.5% reduction in positive tests.

“The paper is still under review, so there is that,” says Khubchandani, emphasizing the need for more research.

Other COVID-19 Vaccines and Transmission

However, in apress release, Johnson & Johnson recently provided preliminary data from its Phase 3 clinical trial for the Janssen COVID-19 vaccine. On February 4, the company said that it had asked the FDA for an EUA.

An Overview of the Johnson & Johnson COVID-19 Vaccine

The vaccine manufacturers have not made explicit claims about the shots' ability to slow or cut transmission, but that information may come later as more research is undertaken.

Khubchandani says that “theoretically, any highly-effective vaccine should reduce symptomatic/asymptomatic carrying of virus and its transmission. But proof is still needed in practice.”

One Month Into the Rollout, Here’s How Americans Feel About COVID-19 Vaccines

“There have also been some limited data for Moderna’s vaccine that were included in its FDA briefing document,”Michael Haydock, therapeutic area director at Informa Pharma Intelligence, tells Verywell. He adds that the data from Moderna “suggested a ~63% drop in asymptomatic infections after the first dose in vaccinated subjects vs control subjects.”

Based on clinical trials, the Pfizer-BioNTech vaccine is 95% effective at preventing laboratory-confirmed COVID-19.The Moderna vaccine is reported to be 94.1% effective.According to Johnson & Johnson, its single-dose vaccine shows 85% efficacy in preventing severe disease across all regions studied.

Based on clinical trials, the Pfizer-BioNTech vaccine is 95% effective at preventing laboratory-confirmed COVID-19.The Moderna vaccine is reported to be 94.1% effective.

According to Johnson & Johnson, its single-dose vaccine shows 85% efficacy in preventing severe disease across all regions studied.

Why We Have to Slow the Spread

Efficacy rates are important to spare people from severe illness and death from COVID-19 and to ease the burden on the healthcare system. However, stopping virus spread is also a huge factor in getting to the other side of the pandemic.

“It is key that we vaccinate people faster,” Khubchandani says. “And also have vaccines that reduce transmission from person to person—even from the vaccinated people.”

If we hope to eradicate the virus, reducing transmission is key.

If someone who is vaccinated cannot transmit the virus, that adds another element to vaccine protection. Not only will vaccination protect the individual receiving the shot, but it also helps to protect anyone that person comes into contact with who have not been vaccinated.

Does it Matter Which Vaccine You Get?

“We are running at a slow pace compared to the virus,” Khubchandani says. “COVID-19 virus spread has been like a wildfire. So we have to be fast, resourceful, be able to use multiple techniques.” Those multiple techniques, he says, include using a menu of vaccines.

5 Ways To Prepare for Your COVID-19 Vaccination

As the list of available vaccines expands, some people may wonder if they should wait to see if they’re able to get the vaccine than the one first available to them.

Jagdish Khubchandani, PhDPeople need to choose vaccine over disease.

Jagdish Khubchandani, PhD

People need to choose vaccine over disease.

Haydock recommends that people “receive whatever vaccines are available at the time.” He adds that all the vaccines that are currently available have been shown to have “good safety profiles and have strong evidence that they are effective at preventing severe infections and hospitalizations.”

The National Institutes of Health (NIH) estimates that 75% to 80% of Americans must get a COVID-19 vaccine before herd immunity is achieved and a “semblance of normal life” can be resumed.

“People need to choose vaccine over disease,” Khubchandani says. “Even a single dose of any vaccine is better than one-time infection with COVID-19.”

So far, according to the Centers for Disease Control and Prevention’s (CDC) COVID Data Tracker, more than 32 million Americans have received their first vaccine dose—only about 10% of the population.

COVID-19 Vaccine Distribution Tracker

Khubchandani says that it’s also important to continue to dispel fears about getting vaccinated. “I have worked in medical schools, basic science labs, and now in the field of behavioral and social sciences. No one wants to harm people,” he says. “No person in a scientific profession thinks like that. There is rigorous training and oversight in whatever is being done with vaccine development.”

What This Means For You

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit ourcoronavirus news page.

9 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Voysey M, Costa Clemens SA, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al.Single dose administration, and the influence of the timing of the booster dose on immunogenicity and efficacy Of ChAdOx1 nCoV-19 (AZD1222) vaccine.Preprints with The Lancet.University of Oxford.Oxford coronavirus vaccine shows sustained protection of 76% during the 3-month interval until the second dose.Food and Drug Administration.Pfizer-BioNTech COVID-19 vaccine.Food and Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces submission of application to the U.S. FDA for emergency use authorization of its investigational single-shot Janssen COVID-19 vaccine candidate.U.S. Food & Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its Phase 3 ENSEMBLE Trial.Collins F.Celebrating the gift of COVID-19 vaccines.Centers for Disease Control and Prevention.COVID data tracker.

9 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Voysey M, Costa Clemens SA, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al.Single dose administration, and the influence of the timing of the booster dose on immunogenicity and efficacy Of ChAdOx1 nCoV-19 (AZD1222) vaccine.Preprints with The Lancet.University of Oxford.Oxford coronavirus vaccine shows sustained protection of 76% during the 3-month interval until the second dose.Food and Drug Administration.Pfizer-BioNTech COVID-19 vaccine.Food and Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces submission of application to the U.S. FDA for emergency use authorization of its investigational single-shot Janssen COVID-19 vaccine candidate.U.S. Food & Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its Phase 3 ENSEMBLE Trial.Collins F.Celebrating the gift of COVID-19 vaccines.Centers for Disease Control and Prevention.COVID data tracker.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Voysey M, Costa Clemens SA, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al.Single dose administration, and the influence of the timing of the booster dose on immunogenicity and efficacy Of ChAdOx1 nCoV-19 (AZD1222) vaccine.Preprints with The Lancet.University of Oxford.Oxford coronavirus vaccine shows sustained protection of 76% during the 3-month interval until the second dose.Food and Drug Administration.Pfizer-BioNTech COVID-19 vaccine.Food and Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces submission of application to the U.S. FDA for emergency use authorization of its investigational single-shot Janssen COVID-19 vaccine candidate.U.S. Food & Drug Administration.Moderna COVID-19 vaccine.Johnson & Johnson.Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its Phase 3 ENSEMBLE Trial.Collins F.Celebrating the gift of COVID-19 vaccines.Centers for Disease Control and Prevention.COVID data tracker.

Voysey M, Costa Clemens SA, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al.Single dose administration, and the influence of the timing of the booster dose on immunogenicity and efficacy Of ChAdOx1 nCoV-19 (AZD1222) vaccine.Preprints with The Lancet.

University of Oxford.Oxford coronavirus vaccine shows sustained protection of 76% during the 3-month interval until the second dose.

Food and Drug Administration.Pfizer-BioNTech COVID-19 vaccine.

Food and Drug Administration.Moderna COVID-19 vaccine.

Johnson & Johnson.Johnson & Johnson announces submission of application to the U.S. FDA for emergency use authorization of its investigational single-shot Janssen COVID-19 vaccine candidate.

U.S. Food & Drug Administration.Moderna COVID-19 vaccine.

Johnson & Johnson.Johnson & Johnson announces single-shot Janssen COVID-19 vaccine candidate met primary endpoints in interim analysis of its Phase 3 ENSEMBLE Trial.

Collins F.Celebrating the gift of COVID-19 vaccines.

Centers for Disease Control and Prevention.COVID data tracker.

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