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How many people who test positive are asymptomatic? Your COVID-19 questions answered.

Detroit Free Press - 3/6/2021

Free Press readers have lots of questions about COVID-19. We've asked experts and tracked down sources to help sort through the information swirling about the virus, the vaccines, and more.

Please continue to ask us questions and we'll continue to seek answers. Submit your questions to us by emailing Free Press health reporter Kristen Jordan Shamus at kshamus@freepress.com and we'll answer as many as we can.

Here's this week's Q&A:

QUESTION: Of the people who test positive for COVID-19, what percentage are asymptomatic? How many have severe illness?

ANSWER: It's estimated that about 20% of asymptomatic people who test positive for COVID-19 won't go on to develop symptoms of the virus, according to a pair of studies published in September in Thorax, a respiratory medicine journal, and Plos, a nonprofit open-access publisher of medical research.

Some who test positive for COVID-19 and don't have symptoms at the time of the test later become ill, and were pre-symptomatic at the time of testing.

However, it's hard to pinpoint how many people are asymptomatic carriers of the virus and never get tested. The U.S. Centers for Disease Control and Prevention uses a range of 5% to 24% of people up to age 65 who are infected but asymptomatic. The range is slightly higher for people older than 65: 5% to 32%.

Research published in JAMA Network in January suggests about 59% of all SARS-CoV-2 transmission is caused by pre-symptomatic and asymptomatic people, which is why it's important when there is a lot of community spread of the virus to wear masks and practice social distancing. It's hard to know who's been infected and who has not.

How sick people get with COVID-19 depends on several factors that scientists are still trying to understand, and include such factors as age and underlying health conditions.

The CDC reports that 46% of Americans who've been hospitalized with COVID-19 were 65 or older; 25% were 50-64; 26% were 18-49; 2% are children ages 5-17, and 1% were infants to age 4.

The risk of hospitalization from COVID-19 more than doubles for people 65 and older compared to people of all ages.

QU: I had COVID in December. I have had both vaccine shots. We live in a remote area and a friend who is sick with COVID needed to go to the emergency room 45 minutes away. I took her with a mask and sanitizer. Do I still need to quarantine?

A: The CDC updated its guidance in February on quarantine requirements for people who've had both doses of a COVID-19 vaccine.

You don't have to quarantine after driving your friend to the ER as long as:

When you drove your friend to the hospital, it had been at least two weeks after your second dose of a coronavirus vaccine. And you got your second dose of a COVID-19 vaccine within the last three months. You don't have any COVID-19 symptoms.

The CDC advises that you should watch for COVID-19 symptoms for 14 days after you were exposed and get a test if you develop symptoms.

Q: I have taken the COVID vaccine, but my wife has not had the opportunity to do so yet. She is now very concerned about me being an asymptomatic transmitter — and thus a health threat to her. Am I now a greater threat for my wife? Should I (or both of us) start wearing masks at home? Should we isolate from each other till she gets vaccinated?

A: Dr. Russell Faust, medical director of the Oakland County Health Division, said even after people are vaccinated, it's a good idea to wear masks when you're out in the community and around people who don't live in your household, to practice social distancing and good hand hygiene.

But being fully vaccinated makes you much less likely to spread the virus to your wife and to others, he said.

"Your infectiousness, let's call it your ability to transmit, the risk of you transmitting COVID-19 to someone else, is parallel to ... the severity of your symptoms," Faust said.

"If you've been vaccinated and infected, you're going to have a much, much lower level of symptoms, much less severe infection, and along with that, a much lower risk of transmitting. If you're completely asymptomatic, and you've been fully vaccinated, ... data suggest that your risk of transmitting to somebody else is extremely low. That is, you're not going to be unwittingly asymptomatically transmitting COVID-19."

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For those reasons, unless you develop COVID-19 symptoms, there is no need to isolate or wear masks at home around your wife.

Q: I am 73 years old and about to have surgery that will require at least one night the hospital. I have not had the COVID-19 vaccine yet. How soon after surgery can I get the vaccine?

A: That's a question your doctors can answer best, Faust said, because each person's situation is unique.

However, he stressed that people shouldn't let concerns about COVID-19 keep them from undergoing surgery or seeking other medical care.

"People are still afraid of hospitals," Faust said. "They need not be.

"I want to reassure readers that ... if you have something going on, if it's chest pain or whatever it is, go to the hospital. Get your surgery. Get taken care of. You're not at risk in the hospital."

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Q: If I make an appointment for a COVID-19 vaccine with a county health department, can I pick which company's vaccine I'll get or know in advance which type will be given to me?

A: People won't be given a choice of which vaccine they prefer, Faust said.

“I need to strongly urge people not to brand shop, not to go brand shopping for vaccines when they're looking to get vaccinated," he said.

Some people have suggested that coronavirus vaccines made by Moderna and Pfizer are better because they have efficacy rates of 94%-95%, while Johnson & Johnson's vaccine efficacy rate in the U.S. is 72%.

But the vaccines should not be compared like that, Faust said. Simply looking at outcomes of the Phase 3 clinical trials does not fully explain how much protection a person will get from each type, and it doesn’t mean one vaccine is better than another.

The Johnson & Johnson vaccine went through trials a little bit later than Moderna’s and Pfizer’s, he said, and was tested globally, including in countries where more contagious variants that originated in South Africa, Brazil and the United Kingdom were spreading.

“What you’re not seeing or hearing with those numbers being reported, you're not seeing people emphasize, is the notion that Johnson & Johnson vaccine clinical trials ran during a time when these variants were running rampant in the community," Faust said.

“And so they ran clinical trials in South Africa and South America and the United States and other places. The fact is, you can’t compare those results with the results that Pfizer and Moderna got in their clinical trials … when we didn't have these variants.

“And so I think we're comparing apples to oranges. For me, what I really care about, ... is: Will this keep me alive if I get COVID-19 infection? That is, does it prevent death from COVID-19? Does it prevent severe infection, severe disease and keep me out of the hospital, off a ventilator?

“And the answer to that appears to be pretty similar to Pfizer and Moderna. So I would not hesitate to recommend it for my own family members. If I weren't already vaccinated, I would certainly consider it."

In phase 3 clinical trials of 40,000 people, none of the patients who received the Johnson & Johnson vaccine were hospitalized with a SARS-CoV-2 infection 28 days following the one-dose immunization, and no COVID-19 deaths were reported in the vaccinated group, according to CDC data.

“My professional advice is that when you get the call, or you receive the email inviting you for an appointment, to get vaccinated,” Faust said. “This is important. We all need to get vaccinated to put an end to this pandemic, regardless of the source.”

Q: Are people with intellectual and developmental disabilities eligible for a COVID-19 shot in Michigan? If so, when did the state expand to that category?

A: Gov. Gretchen Whitmer and the state health department announced expanded eligibility for COVID-19 vaccines starting Monday to include any person 50 and older in Michigan with disabilities or pre-existing health conditions. The broader eligibility also includes parents or guardians of children with special health care needs.

People with disabilities younger than 50 are not eligible for a vaccine unless they qualify under another classification, such as because they live in long-term care, or work in select professions that are considered essential, such as health care, agriculture/food processing, K-12 teachers, child care workers, first responders or law enforcement officers.

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Local health departments also have discretion to vaccinate some other classifications of people. One such example is the city of Detroit, which is offering vaccines to any resident 18 or older with intellectual and developmental disabilities and their caregivers.

You can read more about Michigan's expanded vaccine eligibility guidelines here: https://bit.ly/3c2nM9I. To read about the city of Detroit's vaccine rules, go to: https://bit.ly/3uSSzyi.

Contact Kristen Shamus: kshamus@freepress.com. Follow her on Twitter @kristenshamus.

This article originally appeared on Detroit Free Press: How many people who test positive are asymptomatic? Your COVID-19 questions answered.

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