COVID-19 Resource Center

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Frequently Asked Questions About COVID-19

This information is solely the educated opinion of Prof. Manfred Green and is not intended as medical advice. Please consult your physician.

How is the corona virus spread? Toggle visibility of hidden content.

The coronavirus mutates and changes its genetic makeup very easily and adapts to the immunity of the populationThe more the virus circulates, the more chance it has of it mutating. One of the aims of public health officials is not just to prevent disease, but to prevent circulation. When circulation is prevented, the chance of change or mutation is reduced. The current virus, Omicron, seems to be spreading quite easily. We are still waiting to see what develops, however. 

How long does the virus stay in the body of an infected person? Toggle visibility of hidden content.

It depends on the immune status of the person, but it can stay in the body for quite a while. Therefore, we recommend someone who has been infected to incubate for 2 weeks, on the basis that the virus is still in the person but may not be causing symptomatic disease.  

What are some of the symptoms and long-term effects of COVID-19? Toggle visibility of hidden content.

The symptoms of COVID-19 are typical of a respiratory disease. One of the most typical symptoms is fatigue. People may complain of a sore throat, cough, fever, loss of taste and or smell, and joint pain. It is also possible to have COVID and be asymptomatic. Unfortunately, someone can develop a second phase of the disease that leads to rapid deterioration. The most severe potential complication in this case is respiratory failure. This may cause various parts of the body to fail and is the main reason people die from COVID. These symptoms are much greater in the elderly or people with comorbidities. Fortunately, it generally doesn’t cause severe disease in young people or those under the age of 20. The disease is also generally mild in children. 

The long-term effects of COVID are still not clear or easy to classify. Some effects may last 1-2 weeks. Some long-term effects may include loss of taste and or smell, fatigue, and joint pain. These can persist for weeks and sometimes months. There are significant numbers of people who have symptoms longer, but we are still researching to determine what, if any, permanent impact these might have.       

What is the scientific community’s position on children getting vaccinated? Toggle visibility of hidden content.

First, the vaccine is now widely used for adolescents 12-18 years old and after successful trials for young children 5-11, vaccines are now being implemented in the US and Israel. As with adults, some people may have some mild and temporary side effects, but they are generally tolerable. (There are 8 vaccines approved by the WHO—Moderna, Pfizer/BioNTech, Janssen (Johnson & Johnson), Oxford/AstraZeneca, Serum Institute of India, Bharat Biotech, Sinopharm (Bejing) and Sinovac) *please note not all vaccines are approved for or available in all countries. For more information, please visit There is no reason to suspect that the vaccine will be any less safe for younger recipients. There is some data on the efficacy, and we will follow up to share those results, but the vaccine is safe for children. To cope with the pandemic, we need to vaccinate children. We will not get rid of these infectious diseases without vaccinating children. 

Many question how effective these vaccines will be for young children below the age of 5 years. Some in the public health community are saying the vacccines are 50-60% effective for this population and is close to what we see for the influenza vaccine. I would still recommend giving young children the vaccine.


Why are masks effective and why are they recommended? Toggle visibility of hidden content.

Masks have been routinely used in the medical community for quite some time. Masks have been tested in labs for trapping particles and have demonstrated to be effective. The real question is whether the masks are used correctly. Are people covering their nose and mouth? When used properly, the mask forms a physical barrier and on average, it makes sense to use this simple procedure to reduce potential exposure and slow the spread of the virus. There have been very few controlled studies on the efficacy of masks, so we depend on physical data and experience. 

In the future, it may make sense to encourage the use of masks in closed public spaces during the winter months, which should reduce the spread of the SARS-CoV-2 COVID-19 virus and other respiratory viruses, and provide additional protection over and above the vaccine.

What are the different types of vaccines available and how do they work, respectively? Toggle visibility of hidden content.

The most modern is the mRNA vaccine produced by Moderna and Pfizer. It is a newer technology that takes the RNA from the virus, synthesizes it, creating genetic code for that RNA. Then, researchers coat the new RNA in a lipid layer that destabilizes and takes up the immune cells. The immune system is now primed to generate antibodies to neutralize the virus. The whole concept of a vaccine is to expose a body to part of the virus, your body then produces antibodies so when the actual virus comes, your antibodies recognize the virus and go through a process of neutralizing the virus through antibody production. The mRNA gets your body to produce this protein that is on the surface of the virus. That RNA gets broken down and disappears after a few days. Others, like AstraZeneca and Sputnik vaccines, are the viral vector, where part of the virus is attached to a nonreplicating virus that does not cause disease in humans. Again, this is another way to get the virus into the body to produce antibodies. There are several vaccines that are still being tested. The World Health Organization approved vaccines  

What is a booster actually? Why is it necessary? Might it become like the flu shot that is annual, semi-annual? Toggle visibility of hidden content.

It is impossible to determine how many doses are definitively necessary at this current time. J&J (Johnson & Johnson), for example, was a single dose initially, and now it has been proven that you need a booster. We have vaccines like polio where 6-7 vaccines are given to maintain immunity. It is very much a question about the vaccine and the organism. Most vaccines decline in efficacy over time, and we did not have the data when these vaccines were first introduced to determine how many shots would ultimately be required to effectively offer immunity. We do not claim most vaccines are going to protect you for the rest of your life after only one shot. Right now, to be fully immunized, this should be considered a three-dose vaccine and you may need a booster in the future to maintain immunity.

Is there a downside to getting vaccinated? Any dangers or long, short term implications? Toggle visibility of hidden content.

This vaccine is safe, much like all vaccines. It has a long safety record. There really are no long-term effects of vaccines—at least anything that has been welldocumented. Whatever is injected in, is broken down in our bodies. It is not like a medication that can have long term effects which can damage livers or other organs. There are side effects that could be problematic, for example, for the Pfizer and Moderna vaccines there is a certain risk of myocarditis, an inflammation of the heart muscle, particularly in young males. This is usually a mild disease which does not cause a large amount of morbidity or illness. We need to keep monitoring, but at the moment, we have no reason to feel the vaccine is problematic in any way. 

What determines how contagious a variant might be? Toggle visibility of hidden content.

The mutation is part of the replication process of the virus where it makes mistakes or links up with another virus. It changes the genetic material of the virus and becomes a new strain. The mutation may have a harmful effect or a favorable effect. We do not really know. We tend to notice the bad one since the good one may go undetected. Mutation is something we see with nearly everything. RNA viruses are particularly susceptible because they do not have a particularly good “reading” process when they replicate. 

How effective are the different types of COVID testing? Toggle visibility of hidden content.

There are limitations of the tests and their sensitivities, but it is very difficult to determine windows of contagion. The PCR test, (Polymerase Chain Reaction) is the more sensitive test. It tests the actual genetic material from the virus. It also gives information about the virus. The antigen test only detects if there is an antigen from the virus. It is good as a screening tool for kids going to school or for going to a restaurant but is less sensitive and may be less accurate than the PCR test. The technology will begin to improve, and results depend on how much virus is present in the body. Someone infected yesterday might have a small amount as it begins to replicate, those who have had the virus for two weeks will have more.  

What is the latest with the Omicron variant? Why are people so concerned? Toggle visibility of hidden content.

The recent omicron variant of the COVID-19 virus has created new challenges. It spreads more rapidly and the antibodies produced by the current vaccines are less effective. The good news is that the third vaccine dose of an mRNA vaccine does induce good protection against serious disease from omicron.

In general, the disease caused by the omicron variant is milder than the earlier variants. Although it is too early to be sure, this could be a sign that the newer variants of the SARS-CoV-2 (COVID-19) virus may be less “aggressive”. This may be the path to a situation where the disease is endemic, with tolerable levels of disease. and can be effectively controlled with the vaccines that have been developed.

What do we know about the Omicron BA.2.7 variant and how problematic is it? Toggle visibility of hidden content.

If you had immunity from the first wave of Omicron, you most likely have reasonable immunity to BA.2.7. The population is becoming more and more exposed to these different strains and we have to be optimistic that these strains aren’t going to transform into worse strains. They’ll be a bit different, but the high immunity of the population from infection or from the vaccine or some combination of both should control severe disease.

We will update this space as more information about this variant becomes available.


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Have a question about anything COVID-19 related?

Submit your question below and we’ll address it during the next FB live stream with Dr. Green

About Dr. Manfred Green

Since the onset of the COVID-19 pandemic, Manfred Green, MD, PhD, MPH, Director of University of Haifa’s International School of Public Health Master’s program, has been a steady source of up-to-date information on everything from mask mandates to vaccination development and rollout. Prof. Green is a professor in the University’s Department of Epidemiology and previously served as head of University of Haifa’s School of Public Health. He is an adjunct professor at University of Georgia College of Public Health in the United States, previously served as head of public health for the Israel Defense Forces, and is a founding Director of the Israel Center for Disease Control.

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