Why Testing New Medicines in a Diverse Population Is Important

Updated on Nov 14, 2025 | COVID-19, Engagement, Featured, Research, Vaccines

Companies are working to develop new vaccines for COVID-19, and one of the many challenges is ensuring that clinical trials required to test the new medicines reflect the population at large in order to determine how effective the vaccines will be when offered to tens of millions of people throughout the United States.

In this Q&A, Lynne D. Richardson, MD, Professor and Vice Chair of Emergency Medicine, Professor of Population Health Science and Policy, and Co-Director of Mount Sinai’s Institute for Health Equity Research, talks about the latest COVID-19 vaccines, why it is important for clinical trials to include a diverse population, and how well the pharmaceutical industry has done that.

Based on data you have seen about the most advanced COVID-19 vaccines in development, do you think the pharmaceutical companies have done a good job including a diverse group of people in their clinical trials?

They are all committed to trying to include a diverse population into their trials. I think there have been substantial efforts to improve the diversity of the participants in the vaccine trials. From the data I’ve seen, I think they did an okay job, though ideally, the makeup of the folks in the trials would be the same as the distribution of the disease.

Why is it important to have a diverse group of people in the clinical trials for COVID-19 vaccines?

Trials are a way of getting information about how something works. So if you want to know that it works for people of all ages, people of all races, people of all ethnicities, people who have lots of other medical conditions, these people must be in the trial. This is always true, not just for vaccines. In addition, participation in the trials must be representative of the population that is suffering from whatever condition is being targeted by the vaccine, or the treatment. There are certain communities, specifically Black and Hispanic communities, who we know are being harder hit by COVID-19, both in the chance they contract COVID-19, and the severity of the disease if they do get it. That’s why it’s important to have a vaccine that is safe and effective for those communities.

Lynne D. Richardson, MD

In the past, how well have clinical trials included a diverse population, including people of color and those of different socio economic status?

If you go back 40 or 50 years, clinical trials consisted almost exclusively of white men between the ages of 25 and 65. They were considered the ideal subjects. The problem is, it is very hard to extrapolate the results and findings of the trial to types of people who are not participating in the trial. It was about 30 years ago that a big push to improve the gender diversity in clinical trials came with the establishment of an Office of Women’s Health at the National Institutes of Health, and that’s when the federal agencies that sponsored research started paying attention to who actually was participating in trials. It was about a decade later that significant attention to the racial and ethnic diversity in trial participation emerged. So it’s not a new issue. The degree of under-representation even a decade ago was staggering. About five percent of clinical trial participants were Black at a time when Black people accounted for 12 percent of the population. About one percent were Hispanic at a time when Hispanics were 16 percent of the population.

Why has ethnic and racial representation been so poor?

For patients, there is a legacy of mistrust of research, certainly among the African American population, but also mistrust of the health care system in general and of research, specifically among many disadvantaged populations. They are skeptical about the motives and intent of researchers. Also, there are access issues. Most clinical trial participants are recruited through their physicians, and often companies did not include physicians and practices that serve diverse patient populations.

What can be done about that?

Project Impact of the National Medical Association, a national association of Black physicians, has been working to diversify participation in clinical trials for more than a decade by speaking with Black physicians, who often have a group of patients that is much more diverse. They have published results that show that when Black people are approached in the same way, when they are encouraged to participate by a physician with whom they have a relationship, and whom they trust, they participate at the same rates as other groups. But you have to reach out to the physician and the physician practices, where they have those sorts of relationships.

How has the situation changed during the pandemic?

In the era of the COVID-19 pandemic, with Black people and Hispanics being disproportionately impacted by the virus, it’s essential to engage them in vaccine trials. Yet the level of public distrust in the research process and government has never been higher. So we have a lot of work to do if we’re going to get this pandemic under control.  Building trust means developing relationships and that takes time. This is an ongoing challenge in some of the trials and is why Mount Sinai has been approached by many of the pharmaceutical companies because we do have access to this diverse population.

What is Mount Sinai doing?

At the Mount Sinai Institute for Health Equity Research, we have been approached by various entities, asking us to help recruit more diverse populations into their studies. We start by talking about the things you have to do. First, you have to talk with some of our community partners and you have to accept their input, such as the language you use in the materials you distribute to participants. You need to look at how burdensome the trial will be. If we are going to combat mistrust, we must behave in a trustworthy manner.  The Institute is ready to work with researchers who are serious about building the relationships needed to recruit diverse populations into clinical trials.

 

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Mount Sinai Employees Explain Why They Were Excited to Receive the New COVID-19 Vaccine

Updated on Jun 30, 2022 | COVID-19, Featured, Vaccines

Petrona Ennis-Welch, RN, is one of the first employees to receive the first COVID-19 vaccine from David Reich, MD, President and Chief Operating Officer of The Mount Sinai Hospital and Mount Sinai Queens.

The first health care workers throughout the Mount Sinai Health System received the first new COVID-19 vaccine on Tuesday, December 15. For many, it was an exciting and emotional moment. For these front-line workers, and for the Health System, receiving the vaccine represented a key milestone in the continuing fight against the pandemic, and a critical first step in what remains a long journey back to normal for the New York metropolitan area.

Afterward, some took a moment to explain why they were eager to receive the new vaccine.

“I feel a sense of moral obligation to get vaccinated if it means I’ll be less likely to contribute to further spread of the disease,” said Jamie Piekarski, NP, who provides emergency psychiatric care to patients when they first enter Mount Sinai Beth Israel. Like many others, she decided to receive the vaccine in order to keep herself, her patients, and her family safe. She felt lucky to be among the first employees offered the vaccine. “This is our quickest way back to something close to normal.”

“Getting the vaccine is very emotional for me,” said Matthew Bai, MD, an emergency medicine doctor at Mount Sinai Queens, and an Assistant Professor of Emergency Medicine at the Icahn School of Medicine at Mount Sinai. “We have all been dealing with the pandemic for what seems like an eternity, and every day going to work, COVID-19 is always in the back of your mind. This is a symbol, an actual step toward going back to a normal life.”

He added: “I was not very nervous about the side effects. When you think about it and weigh it against getting COVID-19, then I’ll take the vaccine. So I was happy to get it … I have trust in the science and all the testing that’s been done with the vaccine. I believe it is 100 percent safe. It’s the first effective step we have ever had to actually combat this disease. Before, it was about keeping people alive, and now we are actually trying to stop it in its tracks … This is the light at the end of a very long, dark tunnel.”

Deborah Dean, MD, FACEP, Director of Emergency Medicine, was the first Mount Sinai Brooklyn employee to receive the vaccine, and she was joined by ED Nursing Director Bobby Lynch and ED Administrative Director Sue Stefko, who also received the vaccine.

“I was so excited to receive the COVID-19 vaccine, which I hope marks the beginning of the end of this devastating virus. While it’s disheartening to see so many struggling, I’m encouraged by the hope that this innovative vaccine brings by helping my body create its own antibodies through mRNA,” she said.

“People of color have been disproportionately affected by COVID and, despite our history with health care in this country, I chose faith over fear and will do all I can to protect myself, my loved ones, and my community.”

Ugo A. Ezenkwele, MD, chief of the Mount Sinai Queens Emergency Department and an Associate Professor of Emergency Medicine at the Icahn School of Medicine, said he and all of the staff were excited about the vaccine becoming available. He received the vaccine in order to help protect his colleagues and his family.

“I decided to get the vaccine because this offers some hope. We have been through a lot,” he said. “Furthermore, the science is sound. There have been a lot of people involved in the clinical trials. We also have to thank the scientists who have been working for years in order to get this vaccine to where it is now.”

Amanda Bates, MD, an emergency medicine doctor at Mount Sinai Queens, was looking forward to receiving the vaccine as soon as it was offered. “I have been working in emergency rooms since the pandemic started, and it has been incredibly devastating for patients and their families. I have seen a lot of complications that come from COVID-19 and it’s not something I want for myself, my family, or my patients,” she said. “I trust the vaccine. It is new, but the science behind it isn’t new. I feel confident that any risks that come with a new vaccine are far less severe than the risks that come with getting COVID-19. I think it’s the right thing to do to protect yourself and your community.”

Jonathan Nover, RN, MBA, Senior Director of Nursing in the Mount Sinai Queens Emergency Department, added: “I want to set an example for my team and my family, and I want to put all this behind us. Vaccines are safe, they are proven, and we need to move our lives forward. I feel very lucky and blessed for this opportunity, and I feel happy to let my staff, my family, and my friends know I was able to get the vaccine. I feel really proud of that.”

Althea Reid, is a Patient Care Associate on a behavioral health unit at Mount Sinai Beth Israel. She has been covering on a surge unit while COVID-19 cases increase. She received her COVID-19 vaccine because she wants to do her part to help end the pandemic. “The vaccine also gives me a sense of security and a sense of relief, especially on the bus and train, as I feel nervous about others being as responsible as I want to be,” she said.

Mateow Espinosa, a Care Team Assistant and Scribe at Mount Sinai Beth Israel, said: “A lot of people around me are hesitant to get the vaccine. I feel like it is necessary for me to take the vaccine as a way to educate the people around me. It is also important for me to keep myself and family safe.”

Luis Coello, a security officer at Mount Sinai Beth Israel: “I decided to take the vaccine because I do not want to get COVID-19, and I want to keep my family safe.”

Young Lee, MD, ICU Medical Director at Mount Sinai Beth Israel and an Assistant Professor of Medicine (Pulmonary, Critical Care and Sleep Medicine) at the Icahn School of Medicine: “It was much less painful than the flu vaccine. I decided to take this vaccine to protect myself, as well as my patients and my family.”

Farah Ali, a physician assistant in an emergency department at Mount Sinai Beth Israel: “What a whirlwind, brilliant year for medical science. It is surreal, a little scary, but overall exciting to be among the very first to get this vaccine. I got the vaccine for my Gramma and Grampa.”

Crystal Toribo, PharmD, a pharmacy resident at Mount Sinai Beth Israel: “The side effects of this vaccine are very similar to the flu shot. For anyone who is hesitant to take it, please know that there are so many people here in the hospital to speak to about it, so always feel free to ask questions about side effects and safety. To me, it is important that I get vaccinated so I can protect others, myself, and my family members.”

Michael Ruzzo, RN, who works in an intensive care unit at Mount Sinai Beth Israel: “I have family with pre-existing conditions and I’ve been paranoid about bringing home COVID-19 to them. I also did not see my fiancé for four months during the spring. This vaccine changes all of that.”

Watch a slideshow as employees who work at The Mount Sinai Hospital receive the first COVID-19 vaccine.

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mRNA Vaccine Technology Makes Its Extraordinary Debut

Updated on Jun 30, 2022 | COVID-19, Featured, Research, Vaccines

mRNA vaccines must be stored at extremely cold temperatures.

The mRNA technology used to create the first two COVID-19 vaccines from Pfizer Inc., and Moderna, Inc. will undoubtedly change the course of vaccine development for years to come.

Both companies have “shown that the vaccines are extraordinary,” says Peter Palese, PhD, the Horace W. Goldsmith Professor and Chair of the Department of Microbiology, at the Icahn School of Medicine at Mount Sinai. The Pfizer vaccine began being administered to high-risk U.S. health care workers on Monday, December 14. This marks the first time mRNA technology has ever received authorization for use in a vaccine. Moderna’s vaccine received Emergency Use Authorization from the U.S. Food and Drug Administration (FDA) on December 18. 

“Every single one of the clinical trial participants who received the Pfizer vaccine is thought to have made antibodies against SARS-CoV-2,” which causes COVID-19, says Dr. Palese, who has dedicated his career to the study of vaccinology. Even the 5 percent of participants who did not make enough antibodies to be fully protected made enough to be partially protected against severe disease, he adds. “That is success and that is why everyone is so excited. I hope everyone who is eligible gets vaccinated.”

Like most scientific advances, mRNA technology has evolved over decades. When the COVID-19 pandemic hit in early 2020, mRNA was ready for prime time. The technology was first used successfully in mice in 1990. But it was an unstable molecule that could not be easily transferred into the human body. Over time, improvements in nanoparticle technology enabled mRNA to overcome that hurdle.

This chart shows how messenger RNA vaccines work.

In 2017, mRNA’s safety and efficacy in humans was reported in The Lancet, in a clinical trial of a rabies vaccine. The same year, early human trials began for an mRNA-based Zika virus vaccine. The technology is also being tested for use in cancer vaccines that are now in clinical trials around the world, some in combination with chemotherapy, radiotherapy, and immune checkpoint inhibitors.

Today, synthetic mRNA can be quickly manufactured in a laboratory and engineered to resemble fully mature mRNA molecules that occur naturally in the cytoplasm of the eukaryotic cells of animals. The platform works like a software program that carries the genetic code of the spike protein, an important and easily recognizable portion of SARS-CoV-2. When the code—delivered in a nanoparticle—is injected, the human body begins to make antibodies that recognize and protect against the virus.

The mRNA technology is considered particularly safe since its footprint is so minimal. It does not require the development of inactivated pathogens or small units of inactivated pathogens to trigger an immune response, which is the case with traditional vaccines. In addition, mRNA does not enter the cell nucleus where a human’s genetic material, or DNA, is kept, and leaves the body as soon as it has finished delivering its code. Its main drawback, however, is its high cost due to the intricate lipid preparation of the nanoparticles and the extremely low temperature required to store the vaccines.

Peter Palese, PhD

“If you have mayonnaise and you let it stand, it separates and you get this oily phase,” Dr. Palese says. “It’s the same thing with the mRNA vaccines: they get oily and separate.” The Pfizer and Moderna vaccines require slightly different storage temperatures because they use different lipid particles.

“No shortcuts were taken in the actual scientific development of these vaccines, and we have enough data to know how well they work,” says Dr. Palese. The quick pace of development—which essentially compressed the 10 years it typically takes to develop a vaccine into 10 months, combined with massive amounts of funding—enabled the mRNA vaccines to reach the finish line in record time. Dr. Palese says the closest comparison to such large-scale production took place during World War II during the Manhattan Project, when the United States, the United Kingdom, and Canada joined forces to create nuclear weapons.

In 2020, billions of dollars were provided by the U.S. government, European governments, major corporations, and private donors to fund COVID-19 vaccine development, which, he adds, employed tens of thousands of “really smart people” who were focused on creating safe and successful vaccines.

Dr. Palese expects successful vaccines that use conventional methods will not be far behind those based on an mRNA platform. Within the Icahn School of Medicine at Mount Sinai’s Department of Microbiology, he and his colleagues Adolfo García-Sastre, PhD, and Florian Krammer, PhD, are working on a COVID-19 vaccine that uses an engineered Newcastle disease virus vector. They expect to begin a phase 1 safety trial in January. Dr. García-Sastre is Director of the Global Health and Emerging Pathogens Institute, and Dr. Krammer is Mount Sinai Professor in Vaccinology.

While immediate and widespread COVID-19 vaccinations will help get humanity through the current crisis, scientists fear that SARS-CoV-2 will forever co-exist with humans the same way other infectious pathogens do.

If proven effective, Dr. Palese says Mount Sinai’s low-cost vaccine might be advantageous for use in low and middle-income countries and in young children and infants, who were not part of the mRNA vaccine clinical trials. “Vaccines are good for us,” he says. “They have helped save millions of lives.”

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What Older Adults Need to Know About COVID-19 Vaccines

Dec 10, 2020 | COVID-19, Featured, Vaccines

Older adults are among those most at risk of becoming seriously ill from COVID-19. This is why people who live in nursing homes or other long-term care facilities are expected to be among the first offered the new COVID-19 vaccines. It’s okay to have a lot of questions. You might be wondering, Is it ok to get a vaccine if you have another health problem? What are the side effects? In this Q&A, R. Sean Morrison, MD, the Ellen and Howard C. Katz Chair of the Brookdale Department of Geriatrics and Palliative Medicine at the Icahn School of Medicine at Mount Sinai, addresses some of the common questions older adults may have about these new vaccines.

New Guidance on COVID-19 Vaccines: In April 2023, the Food and Drug Administration and the Centers for Disease Control and Prevention announced some major changes for COVID-19 vaccines. Click here to read more about what you need to know.

When will vaccines be available for older adults living in nursing homes and long-term care facilities?

Older adults living in nursing homes and long-term care facilities will be among the first groups offered a vaccine. However, the exact date will vary state by state.

I am an older adult. If the vaccine is made available to me, should I get it?

I recommend that my older adult patients receive the vaccine. The information we have so far tells us that the vaccines work very well and are safe. Like with any new treatment, there are some things we can’t say with 100 percent certainty. For example, we don’t know if there will be additional side effects that we haven’t seen yet. At the moment, however, we have every reason to think that all people who can get the vaccine, should.

Does the answer to this question change if I live in a nursing home versus somewhere else?

Unfortunately, people who live in nursing homes or long-term care facilities were not included in the studies that have been published so far. The vaccine was found to be safe and effective in older adults living in the community who participated in the clinical trials. Based upon our experience with other vaccines, we do not believe that the risk of side effects for older adults living in nursing homes will be different from those living in the community. Also, based on our experience with other vaccines—particularly vaccines for flu and pneumonia—we do not believe living in a nursing home per se changes the efficacy of the vaccine.

How can I be sure the vaccine is safe for older adults?

All of the vaccines were studied in people over the age of 65. There were no serious issues. As we begin to vaccinate millions of people, we need to watch closely for any side effects that  were not seen in clinical trials, and the Centers for Disease Control and Prevention has a comprehensive plan to monitor for vaccine side effects.

What are the most significant side effects to watch out for in older adults?

The most common side effects appear to be arm soreness, tiredness, headache, and a low-grade fever. At the moment, the recommendations are that if you develop a slight fever after the vaccine, use acetaminophen (like Tylenol) to reduce the fever. Rest if you’re tired. If your arm feels sore, you can use heat or ice, like a hot towel or a bag of frozen peas.

Are there any side effects specific to those with health problems or who are taking multiple medications?

We don’t have enough information about this yet. Patients taking multiple medications and who have multiple conditions weren’t included in clinical trials. Based on other vaccines, we don’t expect any additional side effects. But we don’t yet know for sure.

Does it make a difference which vaccine I get?

Most of us won’t get to choose which vaccine we get. My recommendation is to get the first vaccine that you can. To date, we don’t know if one vaccine is more effective than the other as they have not been compared head to head.

What if I do not want to get the vaccine, or if I’m concerned about side effects?

Based on what we know so far, the vaccine appears to be safe with few side effects. We also know that older adults can get very sick from COVID-19, and are more likely to die from the infection. I compare the risk of getting very sick or dying from COVID-19 with what we know about how safe and effective the vaccine is. I would strongly encourage most older adults to get the vaccine.

Are there some older adults who, because of existing medical conditions, should not get the vaccine?

This is something we think about anytime we’re using a new treatment or vaccine. Based on what we know so far, there are no pre-existing medical conditions that should prevent people from receiving the vaccine.

Why are those living in nursing homes or long-term care facilities at greater risk of contracting COVID-19?

One of the most terrifying things about COVID-19 has been the very high death rate among people living in nursing homes and long-term care facilities. There are three reasons for this. The first is that the patients in nursing homes typically have serious or complex medical illness that weakens their immune systems and places them at higher risk of infection. The second is that COVID-19 can spread easily in a closed community like nursing homes. Lastly, many patients living in these facilities have Alzheimer’s disease or a related dementia and may have difficulty recognizing that they are ill or telling someone that they don’t feel well.

What happens if an older adult in a nursing home or long-term care facility is not able to decide whether to get the vaccine, or if they refuse?

In the United States, a person has the right to refuse medical treatment if they are of sound mind. Many residents of nursing homes have dementia and may not be able to understand the risks and benefits of the treatment being offered. If somebody in a nursing home refuses a vaccine, we would first ensure that they have the capacity to make their own medical decisions.  Specifically, we ensure that the patient understands the benefits and risks of, and the alternatives to, a proposed treatment or intervention (including no treatment).

If they do, then they have the right to refuse a vaccine. If they don’t have the ability to make their own medical decisions, however, we would turn to a designated surrogate decision maker (health care proxy). If the patient has not named a health care proxy, then individual state law determines who would be the decision maker. In most states, this is a family member or next of kin. If there is no next of kin, then we would turn to a court-appointed guardian.

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Mount Sinai Researchers Use Apple Watch to Predict COVID-19

Updated on Jun 30, 2022 | COVID-19, Featured, Research

Subtle changes in an individual’s heartbeat, which can be measured on an Apple Watch, are able to signal the onset of COVID-19 up to seven days before individuals are diagnosed with the infection. That preliminary observation was made by researchers at the Icahn School of Medicine at Mount Sinai in a new preprint from the Warrior Watch Study, which was recently uploaded to the medRxiv server.

The investigators followed 297 health care workers at the Mount Sinai Health System between April 29 and September 29. The participants downloaded a customized app onto their iPhones and wore Apple Watches. Changes in their heart rate variability (HRV)—a measure of nervous system function detected by the Apple Watch—were used to identify and predict whether the workers were infected with COVID-19.

“The watch showed significant changes in HRV metrics up to seven days before individuals had a positive nasal swab confirming COVID-19 infection and demonstrated significant changes at the time of symptom development,” says the study’s corresponding author Robert P. Hirten, MD, Assistant Professor of Medicine (Gastroenterology) at the Icahn School of Medicine at Mount Sinai. Daily symptoms that were collected included fever or chills, tiredness or weakness, body aches, dry cough, sneezing, runny nose, diarrhea, sore throat, headache, shortness of breath, loss of smell or taste, itchy eyes, or none.

Interestingly, the researchers also found that seven to fourteen days after diagnosis with COVID-19, the HRV pattern began to normalize and was no longer statistically different from the patterns of those who were not infected.

Robert P. Hirten, MD

“Developing a way to identify people who might be sick even before they know they are infected would really be a breakthrough in the management of COVID-19,” Dr. Hirten says. “One of the challenging things about COVID-19 is that many people are asymptomatic, meaning they have no symptoms but are still contagious. This makes it difficult to contain this infection by using the traditional method of identifying someone who is sick and quarantining them.”

As a gastroenterologist, Dr. Hirten has been an early proponent of using the Apple Watch and other wearable devices to better understand and manage chronic conditions such as Crohn’s disease and ulcerative colitis. He found that measuring HRV in patients with inflammatory bowel disease helps identify and predict periodic flare-ups. “When the COVID-19 pandemic hit,” he says, “we figured, ‘Let’s try to use the advances we’ve made in studying wearable devices to address the crisis.’”

The Warrior Watch Study, which is ongoing and includes a wide range of Mount Sinai employees—from doctors and nurses to security guards—was designed with two goals in mind, says Dr. Hirten. The first goal was to see whether infection prediction was possible by assessing the data that was collected through the end of September. The other goal was to gauge the effects of the pandemic on the mental health of Mount Sinai’s health care workers. This will be addressed in a separate paper.

“This technology allows us not only to track and predict health outcomes, but also to intervene in a timely and remote manner, which is essential during a pandemic that requires people to stay apart,” says the study’s co-author Zahi Fayad, PhD, Director of the BioMedical Engineering and Imaging Institute and the Lucy G. Moses Professor of Medical Imaging and Bioengineering at the Icahn School of Medicine at Mount Sinai.

Digital health is a relatively new field that holds enormous promise. It provides doctors with patient data that would not otherwise be readily available and requires little input from patients themselves. Mount Sinai’s study asks participants to wear the watch for at least eight hours a day and respond to daily questions that inquire about how they are feeling and whether they have been tested for COVID-19.

Apple Inc. and other wearable device manufacturers are very interested in how their products contribute to health care outcomes, as well. In September, Apple’s Chief Executive Officer, Tim Cook, mentioned Mount Sinai’s Warrior Watch Study during the company’s virtual product launch event.

“This study really highlights where digital health is moving,” Dr. Hirten says. “It shows that we can use these technologies to better address evolving health needs, which will hopefully help us better manage disease in the future. While we aren’t there yet, our goal is to operationalize these platforms to improve the health of our patients. The Warrior Watch Study is a significant step in that direction.”

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How Will We Know Any New COVID-19 Vaccine Is Safe?

Nov 20, 2020 | COVID-19, Featured, Vaccines, Your Health

Vaccines for COVID-19 are in the news these days. For many pediatricians and preventive medicine specialists, vaccines have always been one of their most important tools and one of their most trusted measures for keeping patients healthy. In this Q&A, Kristin Oliver, MD, MHS, a pediatrician and preventive medicine physician at the Mount Sinai Health System and an Assistant Professor of Pediatrics, and Environmental Medicine and Public Health, at the Icahn School of Medicine at Mount Sinai, explains why.

Why are vaccines so important?

Vaccines are one of the best tools we have to prevent disease and death in both children and adults. Getting vaccinated is one of the easiest things that we can do to keep ourselves and our children healthy. When I think about all the things I do to stay healthy—eat well, exercise, manage stress—that’s a lot of work. But it’s easy for me to go and get my flu shot, or bring my kids in to get their vaccines. And when I do that, I’m preventing disease, not just in myself and my family, but also in the communities where I live and work.

How do you measure the effectiveness of a vaccine?

There are two measures of how well a vaccine works. One is called “efficacy,” and that’s how well a vaccine works in a clinical trial. That’s a perfect situation where everybody in the trial who is getting the vaccine doses is getting them exactly when they’re supposed to, and they’re being watched really carefully. Later on, we look at “effectiveness.” That’s in the real world—what happens when people get that second dose a little bit late, or things aren’t in such a controlled setting? For both measures, we compare a group of people who got the vaccine to a group of people who did not get the vaccine, and see how many cases of the disease are in one group compared to the other. You hope that there’s a lot less disease in the group of patients who got the vaccine.

In general, how effective are vaccines?

When you get a disease, how long you have protection from getting it again can vary from person to person and from disease to disease. In the same way, how well a vaccine works also varies depending on the disease and the vaccine. Some vaccines have a really high efficacy rate.  For instance the MMR vaccine that protects against measles has 98 to 99 percent efficacy. Other vaccines are not quite as high. The pertussis (whooping cough) vaccine is closer to 80 to 90 percent. The flu vaccine effectiveness varies from year to year, and is closer to 50 percent. Obviously higher is better. We’re hoping that for COVID-19, vaccine efficacy and effectiveness are closer to 90 percent. But we know that’s not always realistic for every vaccine.

Do we know if the COVID-19 vaccine will be effective for the general population, including children and the elderly?

Right now, we still don’t have a complete answer. Early data from some of the clinical trials looks good. As far as children are concerned, the youngest who have started to receive the trial vaccines are 12. We don’t have enough data yet to know how well the vaccine is going to work in these groups.

If I received the COVID-19 vaccine, can I stop wearing a face mask and social distancing?

Not yet. We don’t know how effective the vaccine is going to be, or how many people are going to receive it.  The recommendation is continue to practice social distancing, wear a face mask, and really good hand-washing. We’re going to have to do this for a little while longer.

How long does a vaccine protect you from a disease?

The protection that you get from a disease, either by having the disease itself and recovering, or by getting the protection from the vaccine, is what we call immunity. This protection depends a lot on the type of disease, and the type of vaccine. Unfortunately, right now, we don’t know how long immunity lasts when you get the disease or when you get the vaccine.

Will a vaccine for COVID-19 get us closer to herd immunity for the virus?

It will definitely get us closer. Immunity is the protection you get either from having the disease, or from getting vaccinated against the disease. With herd immunity, enough people in the community have this protection so that even if someone gets the disease, it is not likely to spread widely. At that point even people who aren’t immune won’t catch it. Right now, we still don’t know what percentage of immunity we need to reach herd immunity.

Can we reach herd immunity by letting everyone get infected?

For diseases where we have safe and effective vaccines, it is much better to reach herd immunity by getting everyone vaccinated than it is by waiting to have everyone get infected. We know the severe, terrible consequences of COVID-19, and so we’re looking for a safe vaccine that can prevent the infection.

Once a vaccine is available to the general public, how do we continue to make sure it is safe?

In the United States, we have incredible systems to track vaccine safety. One system allows everybody to report if they’ve had an adverse event—a bad side effect—after they get a vaccine. That’s not just doctors and nurses; it’s anybody in the public who may have received the vaccine. A group of scientists, working through the U.S. Centers for Disease Control and Prevention (CDC), investigate all of those cases to see if there’s a potential problem. Other systems look at big databases and compare people who have gotten the vaccine to people who didn’t get the vaccine, and look for potential side effects or adverse events, really rare things. They compare the rate in the group who get the vaccine to the group who did not get the vaccine to see if there is a cause between the vaccine and that rare side effect. With all these systems in place, I’m comfortable giving vaccines to my patients, and to my children, because I know that these systems work.

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