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Yale Medicine Vaccine Content Center

July 27, 2021

[Originally published: Dec. 11, 2020. Updated: Feb. 21, 2022]

Note: Information in this article was accurate at the time of original publication. Because information about COVID-19 changes rapidly, we encourage you to visit the websites of the Centers for Disease Control & Prevention (CDC), World Health Organization (WHO), and your state and local government for the latest information.

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.

Will you need a COVID-19 booster shot?

[Originally published: July 27, 2021. Updated: Feb. 14, 2022.]

Even though it seems like only yesterday people were calculating the date they could feel fully protected by their vaccination, boosters are increasingly being recommended for wider swaths of the population.

“The main question is how long the immunologic protection against SARS-CoV-2, which causes COVID-19, lasts,” says Albert Shaw, MD, PhD, a Yale Medicine infectious disease specialist. “And since we are learning about COVID-19 in real time, this is hard to know definitively.” 

We compiled a list of booster-related questions to ask Dr. Shaw.

[Read the article.]

Johnson & Johnson and Guillain-Barré syndrome: What you need to know

[Originally published: Jan. 29, 2020. Updated: Dec. 17, 2021]

Guillain-Barré syndrome (GBS) is a rare neurological disorder in which the immune system attacks the nerves. It can cause muscle weakness and sometimes paralysis. People usually recover from it, but it can lead to hospitalization and, sometimes, permanent damage to nerve cells.

So, it’s not surprising that people have questions upon hearing that about 100 suspected cases of GBS have been identified among 12.8 million people who have received the Johnson & Johnson vaccine. While this figure is low enough to categorize the occurrences as rare, the Food and Drug Administration (FDA) attached a warning (included in fact sheets for patients and providers) in July 2021 to the Johnson & Johnson shot about the increased risk of developing GBS in the 42 days after vaccination.

In December, growing concern over another side effect—a rare number of blood clots in J&J recipients—prompted the Centers for Disease Control (CDC) to endorse a clinical preference for the Pfizer-BioNTech and Moderna shots. But the J&J vaccine is still available; the the FDA and CDC are monitoring the situation and trying to learn more about any relationship between the vaccine and the rare cases of GBS. 

[Read the article.]

How long with coronavirus vaccines last?

[Originally published: May 20, 2021. Updated: Dec. 17, 2021.]

If you are fully vaccinated, you may be excited about gathering with family and friends this summer. But there are still nagging questions about how long protection from the coronavirus vaccines will last. Will it wear off gradually or suddenly? Will you need a booster shot?

“We can only say that a vaccine is protective as long as we are measuring it,” says Yale Medicine infectious diseases specialist Jaimie Meyer, MD, MS

In the meantime, there are a few things we do know.

[Read the article.]

The link between myocarditis and COVID-19 mRNA vaccines

[Originally published: June 1, 2021. Updated: June 24, 2021]

Myocarditis, an inflammation of the heart muscle, became a trending topic this spring when the Centers for Disease Control and Prevention (CDC) reported that it is monitoring a small number of cases of heart inflammation that have arisen in young adults not long after mRNA COVID-19 vaccination. The side effect is considered important but uncommon—arising in about 12.6 cases per million second doses administered. And now the Food and Drug Administration (FDA) has announced it will place a warning on the mRNA vaccines. It’s important to note that the vaccination is still recommended for everyone who is eligible.

[Read the article.]

Herd immunity: An explanation

[Originally published: May 3, 2021. Update: May 21, 2021.]

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.]

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

[Originally published: April 21, 2021. Updated: Dec. 17, 2021.]

Concern has been building over a small, but growing number of cases of a rare, but serious blood clotting disorder associated with the Johnson & Johnson coronavirus vaccine. As a result, in mid-December, the Centers for Disease Control and Prevention (CDC) endorsed their advisory committee’s unamimous decision to give a preferential recommendation to the Pfizer-BioNTech and Moderna vaccines.

[Read the article.]

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

[Originally published: April 14, 2021.]

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

[Originally published: April 12, 2021.]

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.]

Uncommon COVID-19 vaccine side effects no cause for concern

[Originally published: March 30, 2021.]

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

[Originally published: Feb. 24, 2021; updated: Feb. 18, 2022]

As the COVID-19 pandemic enters its third year, the Omicron variant has been driving an uptick in cases in the United States primarily among people who are unvaccinated, and it is even causing infections in some vaccinated people. The good news is that COVID-19 vaccines are still expected to be effective at preventing severe disease, hospitalization, and death from COVID-19.  

We mapped out a comparison of the most prominent COVID-19 vaccines.

[Read the article.]

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

[Originally published: Feb. 10, 2021]

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

[Originally published: Feb. 10, 2021]

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

[Originally published: Jan. 29, 2021]

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

[Originally published: Dec. 18, 2020]

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?

[Originally published: Dec. 10, 2020]

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

[Originally published: Oct. 15, 2020; Updated: Jan. 20, 2022]

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

[Originally published: Oct. 15, 2020]

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.]

Information provided in Yale Medicine articles is for general informational purposes only. No content in the articles should ever be used as a substitute for medical advice from your doctor or other qualified clinician. Always seek the individual advice of your health care provider with any questions you have regarding a medical condition.