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Yale Medicine Vaccine Content Center

May 3, 2021

COVID-19 has changed so many aspects of our lives. Yearning to get back to the way life was before, everyone is looking forward to the introduction of vaccines, a major tool in helping to move past the pandemic.   

Yale Medicine is committed to providing up-to-date information on every aspect of this public health crisis. Our goal for this page, which will be updated as we add new articles and videos, is to provide a resource where you can get answers to your vaccine-related questions and also connect to other information about COVID-19.

Herd immunity: An explanation

Before the COVID-19 pandemic, the term “herd immunity” was possibly something you only heard about during flu season or during reports of upticks in measles cases—if at all. 

But COVID-19 has brought that concept—when an infectious disease is less likely to spread because enough people have immunity either through exposure or vaccination—to the front of our minds. Now that we have effective coronavirus vaccines, many are wondering if and when we will reach herd immunity with COVID-19.

Manisha Juthani, MD, and other Yale experts explain herd immunity, why it matters, and what needs to happen to get there.

[Read the article.]

Yale begins another COVID-19 vaccine trial in children

A clinical trial of the Moderna vaccine is set to begin at Yale for ages 6 months to 12 years. (Yale is one of 90 sites across the U.S. and Canada participating in this trial.)

Since early in the pandemic, Yale has been conducting clinical trials for both adult and pediatric vaccines. This includes a Pfizer-BioNTech study of adolescents that yielded promising results.

We spoke with Inci Yildirim, MD, PhD, a Yale Medicine pediatric infectious disease specialist and a vaccinologist, who is leading this important trial at Yale.

[Read the article.]

The Johnson & Johnson vaccine and blood clots: What you need to know

In the minds of many, the halt of the Johnson & Johnson vaccine in April delivered doubt just as the mass COVID-19 vaccinations were making progress. There are three vaccines authorized for use in the United States, but Johnson & Johnson’s was a particularly important one, partly because its one-shot dose made it seem as though we might achieve herd immunity faster. Then, the government recommended pausing the company’s vaccine after six women who received it developed rare blood clots—and one woman died.

We spoke to Yale Medicine infectious diseases expert Jaimie Meyer, MD, MS, and Yale Medicine hematologist Robert Bona, MD—they shared insights about the pause and answered commonly asked questions.

[Read the article.]

You're fully vaccinated—what can you do now?

Now that many of us have been fully vaccinated against COVID-19, we are now navigating a new gray area—which of the many rules we’ve been following can we now safely ignore?  Our Yale Medicine experts weigh in.

[Read the article.]

Why vaccines may be helping some with long COVID

As more people get vaccinated against COVID-19, a surprise discovery has been that vaccines seem to provide some relief for some patients with what’s being called “long COVID.” A prominent Yale researcher is working with colleagues to launch what she predicts will be a large collaborative study to learn more.

[Read the article.]

COVID-19 vaccines for teens: One step closer

The internet is abuzz with excitement over a press release from Pfizer and BioNTech in which they announced that a Phase 3 clinical trial of their mRNA vaccine “demonstrated 100% efficacy and robust antibody responses” in the trial participants—adolescents ages 12 to 15. (The companies did not yet release detailed data from the trial, and the results have not yet been peer-reviewed.)  

We sat down with Onyema Ogbuagu, MBBCh, a Yale Medicine infectious diseases specialist and a principal investigator in this Phase 3 study. He provided insight into (and context for) the companies’ statement.

[Read the article.]

Uncommon COVID-19 vaccine side effects no cause for concern

Although fatigue and sore arm are typical vaccine reactions, many may not realize that COVID-19 vaccination can, in some cases, also cause other temporary side effects, including swollen lymph nodes or an unsightly arm rash—sometimes called “COVID arm.” Because these reactions are normal, medical experts want to get the word out to avoid alarm for those who experience such symptoms.  

“As more people get vaccinated, it’s important to allay fears and avoid unnecessary testing or treatment for conditions that should quickly resolve,” says Brita Roy, MD, MPH, an internal medicine physician and director of population health for Yale Medicine.  

We sat down with Brita Roy, MD, MPH, an internal medicine physician and director of population health for Yale Medicine; she explains these uncommon symptoms and why they are not cause for concern.

[Read the article.]

COVID-19 vaccine comparison

As the weeks pass, countless reports are coming out about the effectiveness of new vaccines that may be approved. It’s important to keep up, but it’s also a daunting task, given the flood of information (and misinformation) coming at us from so many directions.

So, how do they differ? Here’s what we know so far.

Vaccines from Pfizer-BioNTech and Moderna are being administered in the U.S. right now, Johnson & Johnson just received emergency use authorization (EUA) from the Food and Drug Administration (FDA) for its COVID-19 vaccine in late February, and others are on track to do the same. Even though you will likely not be able to choose which vaccine you will get, it’s still helpful to know how each one is different.

With that in mind, we mapped out the differences between the most prominent vaccines so far.

[Read the article.]

What is it like to get a COVID-19 vaccination?

Two vaccines, one developed by Pfizer-BioNTech and one by Moderna, were each found to be approximately 95% effective in clinical trials and given Early Use Authorization (EUA) by the Food and Drug Administration (FDA) in December 2020. And more are on the way. So, the question remains: What is it like to get a COVID-19 vaccine?   

We made a list of top concerns and asked Onyema Ogbuagu, MBBCh, a Yale Medicine infectious diseases specialist and Yale’s leading expert on COVID-19 vaccines, to share insights.

[Read the article.]

Understanding how the COVID-19 mRNA vaccines work

Much has been made of the fact that the Pfizer-BioNTech and Moderna COVID-19 vaccines involve Messenger RNAs (mRNAs). But how does mRNA work?

In this video, Yale experts Saad Omer, MBBS, MPH, PhD, Onyema Ogbuagu, MBBCh, and Akiko Iwasaki, PhD, explain the science behind these mRNA vaccines.

[Watch the video.]

Why get the COVID-19 vaccination? One woman’s story

Sandra Trevino, LCSW, is a founding member of Yale’s Cultural Ambassadors program—a 10-year-old organization whose mission is to broaden community participation in clinical trials at the Yale Center for Clinical Investigation—and is doubling her efforts to help educate people about COVID-19 vaccines.  

In December, the Kaiser Family Foundation released results of a survey in which more than one-quarter of Americans said they would probably or definitely not get the vaccine. Republicans, and rural and Black Americans were most hesitant, according to the survey. 

“It’s a great responsibility to make sure we continue to address the elephant in the room, which is mistrust with regard to the vaccines,” says Trevino.  

In a recent interview, she explained why she’s encouraging everyone to get the COVID-19 vaccine and talked about her own family’s experience with COVID-19. 

[Read the Q & A.]

The Vaccine is here: Your questions answered

The new COVID-19 vaccine is here. But it’s still hard to know exactly what this will mean in our individual and collective lives.  

For questions—big and small—we went to our foremost expert for a frank, socially distanced question-and-answer session. Onyema Ogbuagu, MBBCh, is a Yale Medicine infectious diseases specialist and the principal investigator of the COVID-19 vaccine studies supported by the Yale Center for Clinical Investigation at Yale School of Medicine, in partnership with the Yale New Haven Health System.

[Read the interview.]

How does the COVID-19 vaccine work?

Vaccines are one of the most effective tools we have in preventing and reducing the burden of infectious diseases. In the midst of the COVID-19 pandemic, vaccines are once again poised to change the tide in our favor in the fight against a deadly virus. But how exactly do vaccines work? And are they safe?

Watch this video to learn more about the fundamentals of how vaccines work, how they are developed, and the importance of vaccination for public health.

[View the video on vaccine fundamentals.]

Vaccine basics

We’ve been told that a vaccine that confers total protection against SARS-CoV-2, the virus that causes COVID-19, would bring a return to normalcy. In March of 2020, health experts said the timeline for an effective vaccine could be 12-18 months—yet, it seems we have one even sooner than predicted. But people are wondering: will it be safe? Will it be effective?  

Yale Medicine has compiled this basic explanation of vaccines—how they work, what’s different from one kind to the next, and the approval process—and what that means for a COVID-19 vaccine.

[Read the vaccine primer.]

Q & A with a vaccine expert

We spoke with Saad Omer, MBBS, PhD, MPH, director of the Yale Institute for Global Health, to get answers to the hard questions on the safety and efficacy of the COVID-19 vaccines in development. The shortened timelines surrounding the development of these vaccines, coupled with concerns over what some feel is undue political influence over the release of them, is concerning to many Americans.  

We sat down with Dr. Omer, who addresses these concerns.

[Read the Q & A.]