How and when will we know that a COVID-19 vaccine is safe and effective?

With COVID-19 vaccines currently in the final phase of study, you’ve probably been wondering how the FDA will decide if a vaccine is safe and effective.

William Petri

Sep 23, 2020

By William Petri

September 23, 2020

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With COVID-19 vaccines currently in the final phase of study, you’ve probably been wondering how the FDA will decide if a vaccine is safe and effective.

Based on the status of the Phase 3 trials currently underway, it is unlikely that the results of these trials will be available before November. But it is likely that not just one but several of the competing COVID-19 vaccines will be shown to be safe and effective by the end of 2020.

I am a scientist and infectious diseases specialist at the University of Virginia, where I care for patients with COVID-19 and conduct research on the pandemic. I am also a member of the World Health Organization Expert Group on COVID-19 Vaccine Prioritization.

What is the status of COVID-19 vaccines in human clinical trials?

Phase 3 studies are underway for the Moderna and BioNTech/Pfizer vaccines and the Oxford/AstraZeneca viral vector vaccine.

Each of these vaccines uses the SARS-CoV-2 spike glycoprotein, which the virus uses to infect cells, to trigger the immune system to generate protective antibodies and a cellular immune response to the virus. Protective antibodies act by preventing the spike glycoprotein from attaching the virus to human cells, thereby neutralizing the SARS-CoV-2 virus that causes COVID-19.

In the case of Moderna’s nucleic acid vaccine, the messenger RNA encoding the spike glycoprotein is encased in a fat droplet – called a liposome – to protect the mRNA from degradation and enable it to enter cells. Once these instructions are inside the cells, the mRNA is read by the human cell machinery and made into many spike proteins so that the immune system can respond and begin producing antibodies against this coronavirus.

The Oxford/AstraZeneca uses a different strategy to activate an immune response. Here an adenovirus found in chimpanzees shuttles the instructions for manufacturing the spike glycoprotein into cells.

Phase 1 and 2 studies by pharmaceutical companies Janssen and Merck also use viral vectors similar to the Oxford/AstraZeneca vaccine, while vaccines by Novavax and GSK-Sanofi use the actual spike protein itself.

Animal tests show the vaccines provide protection from coronavirus infection

Studies in animal models of COVID-19 provide convincing evidence that vaccination with the spike glycoprotein will protect from COVID-19. Experiments have show that when the immune system is shown the spike protein – which alone cannot trigger disease – the immune system will generate an antibody response that protects from infection with SARS-CoV-2.

In studies in hamsters an adenovirus viral vector – the approach used by Oxford/AstraZeneca, for example – was used to immunize with the Spike glycoprotein. When the hamsters were infected with SARS-CoV-2 they were protected from pneumonia, weight loss and death.

In nonhuman primates, DNA vaccines – which deliver the gene for the spike glycoprotein – reduced the amount of virus in the lungs. Animals that produced antibody that prevented virus attachment to human cells were most likely to be protected.

What have the early Phase 1 and 2 studies in humans shown?

Overall, vaccination has triggered a more potent neutralizing antibody response than even that seen in patients recovering from COVID-19.

This has also been the case for Moderna’s vaccine currently in Phase 3 trials and for vaccines from CanSino Biologics and Oxford/ AstraZeneca.

What side effects have been observed?

Physicians have recorded mild to moderate reactions when the subjects were observed up to 28 days after vaccination. These side effects included mild pain, warmth and tenderness at the site of injection, and fever, fatigue, joint and muscle pain.

But Phase 1 and 2 studies are by small by design, with just hundreds of participants. So these trials will not be large enough to detect uncommon or rare side effects.

The emphasis on safety as the primary goal was recently demonstrated in the Phase 3 Oxford/AstraZeneca vaccine trial where one vaccinated individual developed inflammation of the spinal cord. It isn’t clear whether the vaccine caused this reaction – it might be a new case of multiple sclerosis unrelated to the vaccine – but the Phase 3 trial was halted in the U.S. until more is known.

How is the FDA ensuring that a vaccine will be safe yet quickly produced?

The FDA has issued guidance for industry on the steps required for developing and ultimately licensing vaccines to prevent COVID-19 – these are the same rigorous safety standards required for all vaccines.

There are, however, ways to speed the process of approval that are centered on “platform technology.” What this means is that if a vaccine is using an approach such as an adenovirus that has previously been shown to be safe, it may be possible for a company to use previously collected data on toxicity and pharmacokinetics to fast-track clinical trial approval.

While speed and safety may appear conflicting goals, it is also encouraging to note that the rival vaccine manufacturers have jointly pledged not to bow to any political pressures to rush vaccine approval, but to maintain the most rigorous safety standards.

How protective does a vaccine need be to receive FDA approval?

The FDA has set the bar for the primary endpoint of a Phase 3 trial of 50% protection for approval of a COVID-19 vaccine.

Protection is defined as protection from symptomatic COVID-19 infection, defined as laboratory-confirmed SARS-CoV-2 infection plus symptoms such as fever or chills, cough, shortness of breath, fatigue, muscle aches, loss of taste or smell, congestion or runny nose, diarrhea, nausea or vomiting.

This means that an effective vaccine is considered one that will reduce the number of infections in vaccine recipients by half. This is the minimal protection that is anticipated to be clinically useful. That is, in part, because lower levels of efficacy could paradoxically increase COVID-19 infections if it leads vaccinated people to decrease mask wearing or social distancing because they think they are completely protected.

Since a vaccine might be more effective at preventing severe COVID-19, the FDA instructs that protection from severe COVID-19 should be a secondary endpoint.

How many people have to be vaccinated to know if a vaccine works in Phase 3?

The current Phase 3 trials are enrolling 30,000-40,000 subjects. Most of these participants will receive the vaccine and some a placebo.

When, exactly, the results of Phase 3 studies will be released depends in large part on the rate of infection in the placebo recipients. The way that these vaccine studies work is that they test if naturally acquired new coronavirus infections are lower in the group that received the vaccine compared with the group receiving the placebo.

So while it is good news that COVID-19 infections have dropped recently in the U.S. from 70,000 to 40,000 cases per day, this drop in new infections may slow the vaccine studies.

Will Emergency Use Authorization fast-track vaccine?

In an emergency such as we are faced with the COVID-19 pandemic, with approximately 700 new deaths and 40,000 new cases per day right now, the FDA is authorized to allow the use of unapproved products for the diagnosis, treatment and prevention of disease. That includes a vaccine.

The standard approval process for vaccines can require more than one year of observation after vaccination. If the short-term safety is good and the vaccine works to prevent COVID-19, then the vaccine should be approved for use under an Emergency Use Authorization while it is still being studied.

Under Emergency Use Authorization, the FDA will continue to collect information from the companies producing the vaccines for benefit and harm, including surveillance for vaccine-associated enhanced respiratory disease or other potentially rare complications that might be observed in only one in a million.

What should we expect in terms of approvals?

I expect that the FDA will approve several vaccines by the end of 2020 under its Emergency Use Authorization authority so that vaccination can begin immediately, starting with high-risk groups including first responders, health care personnel, and the elderly and those with preexisting medical conditions.

This will be followed rapidly with roll-out of vaccination to the population at large, while all of the time the FDA and vaccine manufacturers will continue to monitor for side effects and work to improve upon these first vaccines. This process is expected to take months.

It may not be life back to normal next year, but all signs point to a healthier 2021.

William Petri is a Professor of Medicine at the University of Virginia.

This article originally appeared on The Conversation. You can read it here.

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Photo credit: Canva – Researchers found what's preventing us from living longer.

Health, Research

New Russian research suggests that the human lifespan could be up to 156 years

Humans can live much longer if certain barriers are addressed.

Erik Barnes

7/31/2026

According to the Guinness Book of World Records, the oldest person lived to the ripe age of 122 years old. Such a lifespan is an incredible feat, but what if the average person could beat that record by 34 years? Recent research done in Russia has led scientists to believe that the average human lifespan could be up to 156 years.

The researchers at Skoltech Biomed Technologies Center developed a mathematical model that allowed them to “switch on” a variety of aging mechanisms. This allowed them to calculate a human’s lifespan where mortality risk never increased with age. After experimenting with different scenarios and conditions, they found the biggest barriers to longevity were caused by non-renewable tissues and somatic mutations.

What are these barriers against longer life?

Somatic mutations are DNA changes within a cell. They accumulate over time during a human’s life and cannot be reversed with any existing therapy. These DNA errors that pile up in our cells contribute to the aging process.

Many human organs like the liver and skin continually replace cells and regrow damaged portions of themselves. However, there are two organs that can’t do this: the brain and the heart. Brain tissue (neurons) and heart tissue (cardiomyocytes) cannot regenerate. This proves to be the most prominent biological limit that shortens our lifespans. This explains why issues like dementia and heart disease are prominent causes of death and morbidity later in life. Since those organs’ tissues don’t replace damaged cells, they’re prone to irrevocably decline over time.

“The key finding of the study is the discovery of substantial differences between tissue types. Neurons and cardiomyocytes, which lack the ability to divide, turned out to be the main limiting factors: when all other causes of aging are eliminated, somatic mutations alone reduce the theoretical median lifespan from 1,759 years (for a hypothetical non-aging human organism) to 156 years,” said Evgeny Efimov, a research intern at the Skoltech Biomed Technologies Center, researcher at AIRI, and one of the key authors of the study.

This suggests that somatic mutations and DNA damage is what ultimately prevents humans from living indefinitely, even if our brains and hearts regenerated cells like other organs.

So what’s next?

Now knowing these biological limitations, the researchers hope to study other areas of aging impacting the human lifespan that could plausibly be reversed. This includes mitochondrial dysfunction, telomere shortening, epigenetic drift, and loss of proteostasis.

The hope is to have a clearer priority list of issues for future therapies to tackle. This is not just to possibly extend life, but to improve lives in general. By developing a fully comprehensive theory of aging, Skoltech hopes to pinpoint which aspects of aging are within our scope to address. After all, thoroughly studying each puzzle piece that makes up human life gives us a better understanding of the whole.

Of course, other impactful factors in a person’s lifespan can be addressed today. As most know, things like diet, sleep, and exercise are among them. A person’s living environment can also negatively impact their lifespan if it doesn’t have clean air, access to clean water, and so on.

For now, the best method for living long is to follow instructions from your physician. Whether you make it to 156 years or not, living well is best for whatever time you’re given.

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Photo credit: PeopleImages/iStock via Getty Images – What kids are doing on tablets seems to matter more than how long they use them.

Health, Well-being

Screen time guidelines for kids and adolescents have shifted as research paints a more nuanced picture

Quality matters more than the clock.

Good Partner

7/20/2026

Gabriel E. Hales

Concerns surrounding young people’s screen time are widespread.

Australia became the first country to ban social media for users under 16 in December 2025, and Denmark, France and the U.K. have since announced similar restrictions to begin this year.

In the U.S., as of mid-2026, more than 30 states have passed laws banning or restricting cellphones in K–12 classrooms; in 2023, the U.S. surgeon general issued a formal advisory on social media and children’s and adolescents’ mental health; and bestselling books tell parents that smartphones are “rewiring” their children’s brains.

These concerns and policies are part of a quickly changing national and international conversation around how young people spend time on screens and its relationship to their overall health and development. My reading of the mounting research on this issue across disciplines is that the popular narrative blaming screens and smartphones for an adolescent mental health crisis runs well ahead of the current evidence.

I study adolescent digital media use and its influence on social, emotional and academic outcomes. A growing body of research suggests that one-size-fits-all solutions are not the answer and that managing appropriate use of digital media needs to take into account a child’s developmental milestones, how parents and adults around them use media, and the ways kids use it to connect and learn with friends and family.

Screen time: From monolith to multifaceted

Wide adoption of digital media and the internet broadened the range of experiences young people could have online. At the same time, the digital age introduced newfound uncertainties. As with the advent of radio, comic books and arcades, adults worried about how children might interact with or be affected by internet use.

In response, the American Academy of Pediatrics first recommended in 1999 that parents and caregivers keep children under 2 away from screens. In the decades since, professional guidance largely treated children’s media use as a behavior to be mitigated.

Policies introduced by the academy in 2013 and 2016 continued to advise that school-age kids and adolescents – those ages 5 to 18 – be restricted to no more than two hours of “entertainment” screen time a day. The goal was to curb risks associated with heavy media use, among them disrupted sleep, online safety, cyberbullying and physical inactivity.

Originally created for young people’s engagement with stationary media that tend to be confined to one room or context – for example, watching television – these hourly limits became outdated with the integration of smartphones and other digital devices into everyday life. Compared with watching television, online media was far more difficult to track and define, and more nuanced in its use.

Developmentally beneficial activities such as education, socializing and leisure have come to rely on the internet to extend and maintain face-to-face connections. Remote schooling and social distancing during the COVID-19 pandemic only accelerated this digitization of daily life.

In my view, adopting strict time limits and restrictions could pose risks to children’s well-being, autonomy and development, for example, by harming adolescent self-esteem.

The latest guidelines

In January 2026, the American Academy of Pediatrics retired its decade-old framework that had largely organized its advice around hourly screen limits. The new policy statement on children, adolescents and digital media diverges from this blanket approach. Instead, it suggests parents consider the larger picture in which this media use exists rather than lumping all screen use together.

Similar to the World Health Organization’s 2019 guidance for children under 5, the American Academy of Pediatrics still advises that parents avoid screen media for children younger than 18 months. This recommendation is largely because extended use by children by themselves can be problematic for many young children, crowding out important developmental milestones.

Both the World Health Organization and the American Academy of Pediatrics also recommend that when children under 24 months use screens, they should be limited to content and devices that encourage children and caregivers to interact. For ages 2 to 5, screen time – including TV and interactive apps on devices – may be extended to more solo use, provided it’s high-quality digital media designed around learning goals in mathematics and reading. But recreational use should be limited to roughly an hour per day.

For school-age children and teens, the newest guidance has begun to step away from fixed screen time limits and asks families to weigh online activity in the context of everyday life.

Doing so recognizes that a child’s digital experiences are shaped by diverse factors rather than the hours spent online. Current guidelines call on caregivers to distinguish among types of media, from television and social media to video games and interacting with artificial intelligence chatbots. They also call for taking into account a child’s individual characteristics, such as their interests and personality, family members’ own use of screens, and the type of content children are spending time on.

Rethinking screen time

Moving beyond strict screen time limits includes questioning the kind of digital activities kids and adolescents participate in. Do the activities encourage time spent interacting with others online, which can help young people develop important skills and competencies?

Scrolling an algorithm-based, auto-playing video feed likely does not equate to the same opportunities as video-chatting with friends, creating digital art or working with teammates in a multiplayer game. Research suggests these different uses relate to development in different ways and can help kids develop varying skill sets pertaining to everyday life and schooling.

Indeed, a large review of current research found that young people who take part in a range of digital activities, such as browsing the web, online gaming or interacting on social media, show positive associations with social connection, identity exploration, civic participation and learning.

Parental involvement in young children’s screen time has developmental benefits. Cultura Creative/Tetra images via Getty Images

Using these guidelines at home

The current evidence suggests parents and caregivers are best positioned to be digital instructors. Cutting children off altogether can carry its own risks for social and emotional development. Caregiver mediation of children’s screen time can produce widely different outcomes and effects, depending on whether the guidance is supportive or controlling.

Considering your own digital media use is the first step: Are family members engaging in problematic or heavy media use that children in the household might emulate? What applications and uses are most common in the family, and what positive or negative effects might they have, depending on the child’s age? How could these digital activities be safely integrated with other everyday experiences to increase their benefit for children? Conversely, what online time might be better spent on face-to-face experiences?

The American Academy of Pediatrics’ Family Media Plan tool turns these ideas into concrete questions. For example, it recommends working out what each child needs from digital technology, what activities screens might be crowding out, and where their family or household can build in screen-free time. The recommendation is to talk with each child about why they are drawn to particular apps or online activities, what they encounter while browsing, and what might be lost when kids bring phones to gatherings such as mealtimes.

The debate over young people’s screen time is not going away. But the most up-to-date guidelines, and the growing body of research behind them, make a strong case for a more holistic approach. The guidelines treat digital media as a complex, diverse and evolving environment that children need to learn to navigate in the digital age. The risks and rewards depend, as with any developmental setting, on the child, the content and what online time might be crowding out.

This article originally appeared on The Conversation. You can read it here.

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Photo credit: Canva – A boy rides an e-scooter, left, while a girl is examined in an emergency room.

Care, Health

ER doctor and mom sets the record straight for parents of kids with e-bikes and e-scooters

At least put on a helmet. And shoes.

Erik Barnes

7/20/2026

An emergency room doctor and fellow mom has been noticing a troubling trend: Many parents are giving their kids something more powerful than bicycles to get around the neighborhood. As a result, she’s seeing more children come into the ER with injuries sustained in e-bike and e-scooter crashes. She recently went online with a plea to parents and young riders.

Dr. Meghan Elizabeth Beach Martin, known online as Dr. Beachgem, posted a video in her scrubs discussing her concerns after seeing so many children come into the hospital with e-bike injuries during the summer months. She’s worried that too many kids and parents don’t understand the proper safety precautions. As a mother herself, she even questions why children are allowed to ride these devices at all.

In the video, the doctor explains that some e-bikes can reach speeds of up to 28 mph. She says that if an e-bike goes any faster than that, it’s technically classified as a motorcycle. At those speeds, she regularly sees children with traumatic injuries and broken bones after hitting bumps, cracks in the road, or other vehicles. Many of them aren’t wearing helmets or protective pads, and some are even riding barefoot, making their injuries even more severe. Martin’s video has gained traction on Reddit and elsewhere online.

E-bikes and e-scooters, examined

Martin isn’t the only professional seeing a growing problem. The American College of Surgeons reports that there are more than 20,000 e-bike-related injuries each year. Meanwhile, a University of California, San Francisco study found that e-bike injuries doubled annually from 2017 to 2022. The same study found that e-scooter injuries increased by 45% each year during the same period.

Before riding an e-bike, it’s important to follow proper safety procedures. Make sure you and your child understand your area’s laws regarding e-bikes, including any minimum age requirements. Always wear a helmet and other protective gear when riding. Consider choosing an e-bike with safety features such as motor-interrupt brake levers and disc brakes. These are just a few of the many safety tips experts recommend.

The U.S. Consumer Product Safety Commission has similar safety tips for e-scooter riders. Wearing a helmet is one of its top recommendations, along with taking other basic precautions. The agency also recommends checking the brakes before riding and slowing down for bumps, cracks, and other road hazards.

The vast majority of e-scooters and e-bikes are designed for only one rider, so avoid doubling up. Although laws vary by state and locality, wearing more protective gear is always the safer choice. Riders should also review local e-bike and e-scooter laws to make sure they are operating the vehicles safely and legally.

A little research goes a long way toward making sure you and your children can ride safely. It’s also important for parents to understand that many e-bikes and e-scooters can travel at speeds that make them very different from a traditional bicycle. The last thing you want is for you or your child to become another emergency room statistic.

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