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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Health, Well-being

Therapist shares 5 ways to be ‘less annoying’ in conversations and it’s a must-watch

None of these habits are malicious. But they sure are annoying.

Mark Wales

5/21/2026

Most people think they come across as helpful, engaged, and supportive in conversations. But according to one therapist, these talking habits may be sending a very different message than intended.

Jeffery, a licensed therapist on TikTok, breaks down five common conversational mistakes people make that can come across as annoying. In the post, viewers didn’t just agree with the list. They began recognizing the same behaviors in friends, family, and even themselves.

Making the conversation about yourself

People can mistake sharing personal experiences for the perfect way to show empathy and compassion. It begins innocently enough when someone opens up about something personal. Unfortunately, the listener responds with a story of their own. Both people are trying to connect, but the focus has now completely shifted.

“When someone constantly redirects conversations back to themselves, people start feeling unimportant,” Jeffery explains. “When every story somehow becomes about you, people stop feeling listened to and start feeling dismissed.”

A 2023 experiment suggested that reciprocal disclosure increases interpersonal trust. However, an imbalance in the conversation can create feelings of one-sidedness. This “stealing of the spotlight” reduces connection.

An unhappy couple gets defensive.
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Getting super defensive

Few things shut down a conversation faster than defensiveness. Even simple misunderstandings can turn tense when people instinctively try to correct rather than understand.

“If every single piece of feedback turns into an excuse or an argument, people eventually stop being honest with you,” Jeffery points out. “Constructive feedback and even some criticism is not always an attack. Sometimes people are simply trying to improve the relationship or communicate something important to you.”

Psychologists describe this behavior as “psychological defensiveness.” Interestingly, a 2024 study found that defensiveness can be reduced if people are warned beforehand in the right way. Conversation works best when it is framed as a collaborative effort rather than an educational or teaching moment.

A woman receives a polygraph test.
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Drilling people after they apologize

There is a delicate balance between asking for clarity after an apology and turning the conversation into an interrogation.

“If someone apologizes and you accept it, but then you keep hammering them over the mistake afterward, it will become exhausting and very annoying,” Jeffery adds. “If people feel like apologizing never actually ends the conflict, they actually become less likely to take accountability in the future.”

People often mistake feedback for a personal attack on their own truth. There’s a popular statement often attributed to Marcus Aurelius claiming that much of what we perceive is shaped by interpretation rather than fact. People can share their opinions. We don’t have to defend ourselves against all of them.

Stop constantly complaining

Everyone deserves an opportunity to vent. But when every conversation circles back to frustration without change, it can become emotionally exhausting for the listener. Over time, even the most supportive friends can start to pull back.

“Talking about problems is normal,” says Jeffery. “But if almost every interaction revolves around negativity, people start associating you with emotional exhaustion. Nobody wants to leave conversations feeling drained every single time.”

This pattern of constant, dissatisfied venting has even found its way into pop culture. Maybe you remember the infamous George Costanza from the award-winning show Seinfeld. His nonstop stream of complaints was a running joke about negativity. It’s fun to watch and laugh at, but far less enjoyable to encounter in real life.

A conversation turns to comparison.
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One-upping people’s negative emotions

Sometimes, someone takes a risk and shares a particularly challenging experience. In an attempt to show empathy, saying “I get it” might land more like “that’s not a big deal.” It’s important to offer emotional validation rather than comparison.

“If someone opens up about something painful and your immediate reaction is to explain how you had it worse, it can make the other person feel completely invalidated,” Jeffery says. “They just want to feel heard and emotionally supported in that moment.”

A 2023 study revealed that someone trying to relate can sometimes redirect attention away from the original speaker. People feel more supported when their emotions are directly acknowledged instead of reframed or one-upped.

A woman reflected in mirrors.
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The comments quickly turn to self-reflection

Many people said Jeffrey’s list felt immediately familiar, whether in conversations with friends or in their own behavior. These annoying habits became surprisingly relatable once someone pointed them out. Here are some of those thoughts:

“silently reposting this for one of my friends to find”

“The first one has ended relationships for me, not because I do it, but because they did it. It’s absolutely exhausting.”

“I know one of my friends are gonna tag me in this later”

“I’ve noticed over the years that my annoying personality will surface when I’m trying to protect myself..”

“I have such a hard time with #1 and I am so aware of it sometimes but I find it so difficult to not do when talking to someone.”

“I do all of these maybe I should go back to therapy”

What might be surprising is that many of these habits are things people slip into without realizing it. Jeffrey’s list doesn’t suggest people are intentionally difficult. He points out that annoying conversations can arise from good intentions, too. Allowing a person to be heard can matter more than offering advice that might fix the problem.

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Care, Health

More women are rejecting ‘optimization culture’ for realistic wellness plans

Feel great and be happy.

Mark Wales

5/16/2026

Being fit used to mean getting enough sleep, drinking more water, and moving your body, perhaps in a daily walk. With the explosion of social media and digital self-help trends, finding an acceptable level of wellness can feel like stepping into a full-time job with daily performance reviews.

For many women, what started as self-care has slowly become another exhausting form of self-optimization. And increasingly, they’re pretty much done with it. According to Women’s Business Daily, one of the biggest wellness shifts happening right now is a move away from extreme routines. Women want habits that actually fit into real life.

An intense workout.
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Wellness feels like a full-time job

Instead of chasing perfection, more women are choosing what can be described as a more realistic approach to wellness, incorporating sustainable routines built around balance and emotional well-being rather than climbing a never-ending ladder of constant improvement.

The shift comes after a solid decade of what many refer to online as “optimization culture.” This exhausting idea assumes that every part of life needs to be carefully measured, improved, and optimized.

Experts believe this mindset is not only making people miserable; it’s unsustainable.

An exhausting routine.
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A backlash against the “always improve yourself” culture

A recent article in Psychology Today found that “wellnessmaxxing” trends turn self-care into another form of anxiety. This is especially true when routines become so demanding that people feel more guilt than relief. As creators post TikToks showing themselves “maxing out” in some kind of self-congratulation, they spread unhelpful expectations that no longer promote self-care.

Verywell Health explains that these influencers broadcast an all-consuming performance metric. People now face a painful realization that they can never do enough. It’s hard to miss the irony that wellness has begun to feel unhealthy.

Women are increasingly embracing low-pressure routines instead of overly aspirational ones. Think walks instead of cross-training, and a morning meditation instead of a week-long stay at a Tibetan monastery. It’s okay to just eat more vegetables instead of a perfectly balanced daily nutrition plan of 150 grams of protein, wheatgrass smoothies, and specifically rated pH-balanced alkaline water.

After all the extreme exercises, self-help books, and sophisticated meal plans, it’s time to get back to basics. Here’s one version of a realistic plan: drink some water, get outside, and try to sleep a little better.

A casual walk with a dog.
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Getting back to the basics

A beauty editor writing for Who What Wear documented her attempt to follow a social-media-inspired wellness reset. With all the expensive and complicated habits she hoped would unlock the “incredibly high-functioning, ultra-productive version” of herself, she came away understanding that she should stick with the basics.

Modern life already asks women to juggle careers, caregiving, appearance standards, finances, and relationships. Somewhere along the journey, wellness became just one more category to add to the pile.

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Women are choosing simple, sustainable routines

Finding realistic wellness is a trend that reflects a growing desire for community-centered wellness rather than isolated self-improvement. Instead of wellness looking like a solo pursuit for an achievement award, many women are leaning toward connection: walking groups, shared meals, accountability with friends, and being honest about feeling burned out on all of it.

The Times reports that people feel walking groups are less intimidating and more emotionally supportive. People don’t just want fitness; they want to belong to something.

A 2025 study in Frontiers in Psychology focused on the benefits of women finding social support groups. Programs that incorporated women’s preferences into their daily lives were more likely to be enjoyed and maintained.

Wellness cultures have told women the answer is to do more: more discipline, more self-reflection, more perfect sleep, more work dedication, more family direction, more effort.

Making life more enjoyable and realistic can help well-being feel easier to maintain. A joyful life is better lived “in” than constantly measured “against” unrealistic expectations.

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Photo credit: MoMo Productions/DigitalVision via Getty Images – Emphasizing the sounds of certain words to young children can help them retain language, not confuse them about speaking properly.

Health, Research

Is baby talk bad? Why ‘parentese’ actually helps babies learn language

Sing-song speech can support early language growth.

Good Partner

5/15/2026

Karen Stollznow

Many parents have heard the warning: Don’t use baby talk with babies and toddlers. Instead, caregivers are often encouraged to speak properly and use adultlike language, out of concern that simplified speech could confuse children or delay language development.

But my research, which I highlighted in in my new book, “Beyond Words,” suggests the opposite is true. The sing-song voice many adults instinctively use with infants, sometimes called “baby talk” but more accurately known as “parentese” or infant-directed speech, actually helps children learn language.

Far from confusing babies, exaggerating phrases like “Loooook at the doggie!” capture their attention, help them detect patterns in speech and strengthen social bonding.

And the funny mistakes children make along the way, such as saying “goed,” instead of “went,” or “mouses” instead of “mice,” are not signs that children are learning language incorrectly. They are evidence that children are actively working out the rules of language for themselves.

Speaking ‘parentese’ to a child doesn’t involve nonsense words. BjelicaS/E+ via Getty Images

What parentese really is

When many people think of baby talk, they imagine nonsense phrases like “goo goo ga ga” or made-up words like “num nums.” But that’s not what linguists and developmental psychologists mean by parentese.

Parentese uses real words and grammatically correct sentences, but with exaggerated intonation, a higher pitch, stretched-out vowels and a slower rhythm. Think of the way a caregiver might naturally say: “Hi, baaaaby! Are you huuungry?”

There is little evidence that occasional playful nonsense words harm children’s language development. But studies suggest that parentese in particular helps babies pay attention to speech, recognize patterns and engage socially.

Adults across cultures tend to speak this way to infants instinctively. Even people who swear they never use baby talk often slip into it around babies.

Researchers have found that infants actually prefer listening to parentese over regular adult speech. The exaggerated sounds and slower pacing make language easier to process. Babies are better able to pick out individual sounds, notice word boundaries and recognize patterns. In other words, parentese helps tune babies into language.

It also strengthens emotional connection. Language learning does not happen in isolation. Babies learn through warm, responsive interaction with caregivers during feeding, play, bath time and everyday routines.

Interestingly, humans are not the only ones who respond to this style of communication. Studies have even shown that cats react more positively when people use a baby-talk voice with them.

Babies are not passive learners

Children do not learn language simply by copying adults word for word. They actively test hypotheses about how language works. That is why toddlers make predictable and surprisingly logical mistakes.

One common example is overgeneralization. A child learns that people form the past tense of many verbs by adding “-ed,” so they produce forms like “goed,” “eated” or “comed.”

These are not random errors. In fact, they show that the child has understood a grammatical rule and is trying to apply it consistently. The problem is simply that English is full of irregular exceptions. The same thing happens with plurals. Children may say “foots” instead of “feet” or “mouses” instead of “mice.” Again, the logic behind these errors is sound.

Linguists sometimes say that children are little scientists, constantly testing patterns and revising their understanding as they receive more input from the world around them.

Why toddlers call everything a ‘dog’

Young children also make predictable mistakes with meaning.

A toddler might learn the word “dog” and then use it for every four-legged animal they encounter. Linguists call this overextension. On the flip side, some children use words too narrowly. A child may use “dog” only for the family pet and not recognize that other dogs belong in the same category. Linguists call this tendency underextension.

These mistakes reveal how children organize and categorize the world around them. They are gradually mapping words onto objects, people and experiences.

Pronouns are another tricky area. Small children often confuse “me” and “you” because these words constantly shift depending on who is speaking. If a parent says, “I’ll pick you up,” the child hears themselves called “you.” But when they try to repeat the sentence, they may not yet understand that the labels switch from speaker to speaker.

This is why toddlers sometimes say things that sound unintentionally cute or confusing. But beneath the confusion is a sophisticated learning process.

Even the Cookie Monster gets it wrong

Children’s speech errors are so recognizable that they often appear in popular culture. Sesame Street’s character Cookie Monster famously says things like “Me want cookie,” while Elmo often refers to himself in the third person: “Elmo wants this.” These speech patterns mirror real stages of child language development. Young children commonly confuse pronouns or refer to themselves by name before mastering forms like “I,” “me” and “mine.”

Despite occasional complaints from adults, there is no evidence that hearing this kind of speech harms children’s language development. If anything, it reflects the natural experimentation children go through.

The Cookie Monster saying ‘Me want cookie’ won’t teach babies and young kids to speak incorrectly. Brian Killian/WireImage via Getty Images

‘Pasketti’ and ‘wabbit’

Pronunciation develops gradually too. Young children often simplify difficult sounds and groups of consonants. “Spaghetti” becomes “pasketti,” “rabbit” becomes “wabbit” and “yellow” may come out as “lellow.”

Speech-language specialists call these simplifications phonological processes. They are a normal part of development because some sounds are physically harder to produce than others. Sounds such as r, th, sh and ch tend to develop later because they require more precise control of the tongue and mouth.

Most children naturally outgrow these pronunciation patterns as their speech matures. However, persistent difficulties can sometimes signal a speech or language disorder, which may require professional support.

Children don’t learn language by copying adults word for word. They learn through interaction, experimentation and repetition. DrAfter123/DigitalVision Vectors via Getty Images

Mistakes are part of learning

Parents are often under enormous pressure to do everything right, including helping their children learn to speak a language. But children do not learn language by avoiding mistakes. They learn through interaction, experimentation and repetition.

Parentese helps babies focus on speech and engage socially. The funny mistakes toddlers make reveal that they are actively piecing together the complex system of language and are often signs of normal development. Language acquisition is messy, creative and remarkably sophisticated.

Speaking in an exaggerated sing-song voice to a baby is not something parents and caregivers need to feel embarrassed about.

Far from harming language acquisition, it may help lay the foundation for it.

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

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