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Your Questions Answered

I have heard that some people are taking ivermectin to prevent COVID-19. What is ivermectin and is it safe?

9.10.2021: Ivermectin is a drug used to treat or prevent parasites in animals, such as livestock and horses. For humans, ivermectin tablets can be prescribed at very specific doses for the treatment of parasitic worms. There are also topical (on the skin) formulations of ivermectin that are used to treat head lice and skin conditions like rosacea. The U.S. Food and Drug Administration (FDA) adamantly states that ivermectin has not been authorized or approved for use in preventing or treating COVID-19. Taking large doses of ivermectin is dangerous and can result in overdose, death and serious health consequences. Ivermectin meant for animals that weigh hundreds of pounds is very different from the tablets prescribed for humans and can be toxic in humans.

Interest in using ivermectin for the prevention and treatment of COVID-19 surfaced, particularly in Latin America, after an early preprint of a scientific study reported that the medication is highly effective in reducing COVID-19 deaths. But that study, which was not subject to peer review, has since been withdrawn due to widespread concerns that some of the data was fabricated and highly flawed. Large randomized clinical trials of ivermectin remain ongoing but at the current time there is a lack of sufficient clinical data to support its use for the treatment or prevention of COVID-19.

Is it safe for me to travel by plane for work if I am vaccinated but my spouse is immunocompromised and I have young children at home who are not vaccinated?

9.10.2021: Vaccines are safe and highly effective in reducing your risk of getting COVID-19 and spreading it to others. But no vaccine is 100 percent effective. So called “breakthrough” infections can and do occur in vaccinated people. Vaccinated people who get infected with COVID-19 are less likely to be hospitalized or become seriously ill, but they can spread the virus to others.

Given these conditions and the current prevalence of the highly contagious Delta variant, you should be aware of the risks involved when considering whether to travel. Unvaccinated adults and those with compromised immune systems should strongly consider not traveling at this time. If you are vaccinated and must travel, the U.S. Centers for Disease Control and Prevention (CDC) recommends taking the following precautions:

  • Wear a mask over your nose and mouth in public (many forms of public transportation such as planes, trains and buses require passengers to wear masks.)
  • Avoid crowds and maintain 6 feet of distance from anyone who is not traveling with you.
  • Wash your hands often and use hand sanitizer containing at least 60% alcohol.

Check your destination in advance and adhere to all state and local requirements upon your arrival. The CDC offers websites that can help with this information for both domestic and international travel. You should also abide by all existing precautions regarding testing and quarantining if you have COVID-19 symptoms, suspect you may have COVID-19 and are waiting for test results, or have been exposed to someone infected with the virus.

Doctors from the Yale School of Medicine provide additional travel guidance in this report.

What is the current research on vaccine booster shots and do people need to get the same vaccine for their third shot or can they get a different one?

8.18.2021: U.S. health and medical experts announced on Aug. 18 that COVID-19 booster shots, so-called “third shots,” should be available to individuals in the United States this fall and possibly as early as Sept. 20. The policy change is just waiting final approval from the U.S. Food and Drug Administration (FDA) and the U.S. Centers for Disease Control and Prevention (CDC).

Booster shots will be available to individuals starting 8 months after their second dose of either the Pfizer or Moderna vaccine. People who received the single-dose Johnson & Johnson vaccine will likely also need a booster shot to maintain immunity against COVID-19 and its mutations such as the highly transmissible Delta variant. But health officials are still collecting data and have yet to make an announcement on a potential booster shot for Johnson & Johnson recipients.

As with initial vaccines, booster shots will be delivered first to high-priority populations such as nursing home residents, health care workers and individuals with underlying health conditions. It is expected that officials will recommend people receive a booster shot of the same brand vaccine through which they were initially immunized. But that guidance has yet to be officially announced.

On Aug. 12, the U.S. FDA authorized third shots, booster shots, for people who have had solid organ transplants or who have otherwise seriously compromised immune systems. That authorization was quickly endorsed by the CDC’s Advisory Committee on Immunization Practices (ACIP).

While initial COVID vaccines remain highly effective in protecting against COVID-19 and its variants, including the Delta variant, scientists believe vaccine potency will eventually lessen over time.

“The COVID-19 vaccines are safe, free, and highly effective – but even highly effective vaccines experience a reduction in protection over time. Today the CDC is announcing new planning for booster shots to protect people and families and stay ahead of the curve on COVID-19,” the White House said in a prepared statement on Aug. 18.

In an interview with CNN, Yale immunobiologist Akiko Iwasaki said: “Vaccine effectiveness is expected to wane” over time…Booster shots are normal. While the immune system’s pathogen-fighting memory cells “are very long lived and they remember the antigens that they encounter the first time, they [memory cells] still need a little bit of encouragement every once in a while.”

As for mixing vaccines, Iwassaki urged caution in a recent interview with National Geographic.

“We shouldn't be mixing and matching just willy-nilly, multiple times,” Iwasaki said. “That's not a good idea…I know that there's a lot of fear out there. But at the same time, scientists are also working around the clock to try to figure out what is the best” timing, mix, and dosage.

If the mRNA used in some COVID-19 vaccines tells cells how to make a coronavirus spike protein, how long does the cell keep making the spike protein once it receives the information? Is it one and done, or does the cell keep making spike proteins continuously?

8.11.2021: According to the CDC, the mRNA in COVID-19 vaccines delivers instructions to our cells to make “a harmless piece” of the spike protein that is found on the surface of the virus that causes COVID-19. This piece of spike protein is enough for our body’s immune system to recognize the virus as an invading germ and to be on alert for it. The vaccine activates our immune system, which then makes antibodies to repel future infection. After the protein piece is made, the cell breaks down the mRNA and gets rid of it. The great thing about vaccines is that they help people to be protected without having to risk getting serious ill with COVID-19 and building antibodies through natural infection.

None of the vaccines authorized for use in the United States contain any of the live virus that causes COVID-19 and the vaccines cannot give someone COVID-19. The mRNA used in COVID-19 vaccines does not enter the nucleus of cells where our DNA (genetic material) is stored and it does not affect or interfere with our DNA in any way. Contrary to claims circulating on social media, the mRNA delivered to cells in the vaccines does not constitute gene therapy, which by definition involves deliberate changes to a person’s DNA. The mRNA vaccines do not change or alter a person’s DNA.

I understand that if we're fully vaccinated but have an underlying medical condition, we should wear a mask in public. But can we remove the mask when we are visiting with a friend or a loved one who is also fully vaccinated or should we leave it on?
8.10.2021: Professor Marney White, PhD, MS ’09, of the Yale School of Public Health’s Department of Social and Behavioral Sciences and Track Director for Critical Topics in Public Health for the YSPH Online Executive MPH Program, responds:

Because the Delta variant is leading to a high number of breakthrough infections, and because even vaccinated people can transmit the virus, it is recommended that you continue to wear a mask.

As an immunocompromised person myself, I understand that these risk-benefit decisions can become very exhausting – especially as guidance continues to change. At one time, I did feel safe around others whom I knew were fully vaccinated. However, now that we know that fully vaccinated people can still transmit the virus, I have changed my approach. If possible, try to schedule outdoor visits with people who do not reside with you. If you must visit indoors, then it is recommended that you continue to wear a mask.
If a person has contracted COVID-19 and recovered, would they then have enough antibodies in their system such that they do not need to get vaccinated?

8.9.2021: Associate Professor of Public Health Jason Schwartz responds:

Individuals who previously contracted COVID-19 will have some antibodies against the virus, but we do not yet know how long-lasting that response is or whether it is sufficient to prevent reinfection, which has been observed during the pandemic. For that reason, vaccination is still recommended for individuals who previously had COVID-19.

Can current COVID-19 tests tell me whether I am infected with a virus variant like Delta? How do people know if they have “regular” COVID vs. one of the variants of the virus?

8.6.2021: Associate Professor of Epidemiology (Microbial Diseases) Nathan Grubaugh, PhD., an expert in genetic disease surveillance who has been studying and tracking COVID-19 variants, answers:

No, most tests will not be able to differentiate between Delta and other variants. All they tell you is if the test detects SARS-CoV-2, the underlying virus that causes COVID-19. Determining if an infection was caused by Delta requires whole genome sequencing, and currently those results can only be used for population-level surveillance, not individual diagnostics. This may change with future tests as they are reviewed by the FDA.

Additional information about the Delta variant from Yale Medicine.

I hear the COVID-19 vaccine can cause heart problems in some children and teens. As a parent with two children (ages 14 and 9), who have yet to be vaccinated, should I be concerned?

Yale School of Public Health Dean Sten H. Vermund, a pediatrician and infectious disease epidemiologist answers:

Fortunately, heart inflammation cases are rare with less than 13 cases per million doses administered in the United States. Death rates from COVID are 608,000 in a U.S. population of 320 million, or 1,875 per million persons. Death rates in vaccinated persons are so low that they are hard to measure right now, though we hope to have estimates in the future. Happily, the heart inflammations have not been serious and have been reversable both with and without medical intervention. The University of Minnesota has a useful article.

A prominent professional basketball player recently tested positive for COVID-19 even though she was fully vaccinated. They said it was a “breakthrough” case. What is a “breakthrough case” of COVID-19 and does this mean the vaccines don’t always work?

Yale School of Public Health Dean Sten H. Vermund, a pediatrician and infectious disease epidemiologist answers:

A lot of people think of vaccines like a bug-zapper that blocks the bug completely. But it’s really more like a bug trapper that has an insecticide built in. It lets the bug in but prevents the invading bug from harming you. With vaccines, you can still get the virus, but it doesn’t do you much harm since your immune system responds so quickly, having been prepared by the vaccine. So the beauty of the COVID-19 vaccines is that they prevent you from getting seriously ill, but some vaccinated people might still get the virus and much milder disease. This Washington Post article explains “breakthrough” infections in more detail.

My 63-year-old uncle is refusing to get vaccinated because he’s afraid he might get Guillain-Barré syndrome if he gets the shot. Is this true?

The U.S. Food and Drug Administration recently added a warning to Johnson & Johnson’s COVID-19 vaccine based on preliminary reports of a very small number of cases of Guillain-Barré syndrome in patients who received the shot. The cases were usually identified about two weeks after vaccination, and they occurred mostly in men age 50 and older. Guillain-Barré Syndrome is a neurological condition in which the body’s immune system damages nerve cells, causing muscle weakness and sometimes paralysis.

But the number of people identified with the rare neurological disorder in connection with the J&J vaccine is extremely small - only 100 people out of 12.8 million doses given. The FDA has described the chances of getting Guillain-Barré from the J&J vaccine as “very low.” Your uncle also has other options for being vaccinated if he is concerned. No data has been presented to date linking either the Pfizer-BioNTech vaccine or the Moderna vaccine to any Guillain-Barré symptom side effects. Both of those vaccines use different technology than the J&J vaccine.

I have had COVID-19 and have received the two-shot Pfizer vaccine (no reactions). Can I get this new strain of COVID in Missouri?

If you’re referring to the COVID-19 Delta variant, which health officials suspect is driving a surge of new COVID-19 cases in Missouri, then the answer to your question is that you are probably safe given your current vaccine status. Scientists are still studying how different vaccines protect against the highly infectious Delta variant, but early indications are that the vaccines available in the U.S. – including the Pfizer-BioNTech vaccine – are protective against the Delta variant once a person is fully vaccinated (two weeks after second dose for the Pfizer vaccine). A recent study by Public Health England found that the Pfizer vaccine was 88% effective against symptomatic disease from the Delta variant. The Moderna vaccine is also reported to offer protection against the Delta variant, according a recent announcement by the company. On July 1, 2021, the Johnson & Johnson company reported that its vaccine was effective against the Delta variant. Missouri is one of several states federal health officials are watching closely due to the high number of individuals who remain unvaccinated there. In some Missouri counties, less than 30 percent of the population is fully vaccinated. The surge in new COVID-19 cases potentially driven by the highly contagious Delta variant underscores the importance of getting vaccinated to protect personal health and the health of others in your community.

There are many of us who cannot take or do not want to take the COVID-19 vaccine. Are there therapeutics available to treat people who become infected with COVID-19?

According to the Centers for Disease Control and Prevention (CDC), “The spectrum of medical therapies to treat coronavirus disease 2019 (COVID-19) is growing and evolving rapidly, including both drugs approved by U.S. Food and Drug Administration (FDA) and drugs made available under FDA emergency use authorization (EUA).” The National Institutes of Health (NIH) has updated information on these approved therapeutics as well as treatment guidelines for clinicians. For those choosing not to receive a COVID-19 vaccine, the CDC strongly recommends continuing to wear masks, practicing physical distancing, and good hygiene, including thorough hand washing.

Note: On June 17, 2021, the Biden administration announced it was investing $3 billion for the development of pills to fight the coronavirus. If all goes well in clinical trials, some of the most promising pills could be available by the end of the year, according to the New York Times.

I am 72 years old and experienced mild symptoms of COVID-19 last year. On several occasions since then, I have experienced audio hallucinations and on one occasion a visual hallucination. Could this be related to COVID-19?
If you are experiencing a specific health problem that is concerning to you, it is important you contact your health care provider right away. Some people who have had COVID-19 continue to experience symptoms months after their initial diagnosis. These so-called “COVID long-haulers” have reported symptoms such as brain fog, dizziness, fatigue and headaches. The best thing to do is to contact your health care provider. This article from the American Medical Association explains more. If you are experiencing any of the COVID-19 emergency warning signs – trouble breathing, persistent pain or pressure in your chest, new confusion, inability to wake or stay awake, and pale, gray, or blue-colored skin, lips or nail beds (depending on skin tone), the Centers for Disease Control and Prevention (CDC) recommends that you seek emergency medical care right away.
I hear that there is a microchip in the COVID-19 vaccine that can be used as a tracking device once it is delivered into my body. Is this true?
There are absolutely no microchips in the COVID-19 vaccines. This rumor is believed to have started due to a misunderstanding about state electronic vaccine records. These digital records are kept by individual physicians on computer rather than on paper as part of the routine modernization of recordkeeping. Electronic patient medical records also allow health care providers to share information about a patient more easily when they are undergoing specialized treatment or in an emergency. But there are no electronic components in the COVID-19 vaccines or in any vaccines.
Could you please define vaccine efficacy according to vaccine protocols?
There are multiple outcomes in each trial, typically some variation of these: COVID-19 infection and COVID-19 severe disease. Vaccine efficacy is calculated by comparing the incidence (proportion of persons within the time period who reach the defined endpoints of infection or disease) in the vaccine group with the incidence in the unvaccinated group. An example can help: a 95% vaccine efficacy means that instead of 10,000 COVID-19 cases in an unvaccinated population of 1 million (assuming 1% would get COVID-19 and 99% would not get it), there would be 500 cases (99.95% of the vaccinated population would be disease-free compared to 99% of the unvaccinated population).
How long is a typical long-term study for these vaccines?
These vaccinees will be studied for years, I think. But the “post-marketing surveillance” demanded for new products by the FDA brings in safety data and will also assess how fast (or whether) immune responses wane with time. This can be done in many more persons that those who were in the clinical trials.
The COVID-19 vaccines were made at “warp speed.” Have they been around long enough to really know if they are safe?
The COVID-19 vaccines approved for use have been extensively tested. Those tests have been independently verified by hundreds of scientists. Due to the public health emergency created by COVID-19, scientists around the world joined together in sharing critical information that resulted in the new vaccines being developed at unprecedented speed. But no steps were bypassed or overlooked. These vaccines went through the same rigorous review required of any new vaccine.
Will the vaccine give me COVID-19?
Pfizer/BioNTech’s and Moderna’s mRNA vaccines do not contain live SARS-CoV-2 coronavirus, so they cannot infect you with COVID-19. The Johnson & Johnson vaccine uses a modified adenovirus to carry the genetic code your body needs to fight COVID-19. Adenoviruses are mostly known to cause mild cold-like symptoms, but scientists altered the adenovirus used in the vaccine so that it won’t cause any disease.
Will the vaccine change my DNA?
The messenger RNA used in the Pfizer and Moderna vaccines does enter your cells, but it stops there. It doesn’t enter the nucleus of your cells that contain all of your DNA. And just like in Mission: Impossible, the mRNA is destroyed by the cell after it receives its instructions.