Will herd immunity save us? Your COVID-19 questions answered

We're answering your questions about the pandemic. Send yours to and we’ll answer as many as we can. We’ll publish a selection of answers every weekday online, and also put some questions to the experts during The National and on CBC News Network.

From herd immunity to ironing masks, here's what you’re asking us today

Most experts suggest herd immunity cannot be achieved safely without a vaccine, because seniors and other vulnerable populations with suppressed immune systems would be at risk and hospitals would be overwhelmed. (Blvdone/Shutterstock)

The information in this article was current at the time of publishing, but guidelines and advice can change quickly. Check with your local public health unit for the most-current guidance, and find the latest COVID-19 news on our website.

We're breaking down what you need to know about the pandemic by answering your questions. You can send us your questions via email at, and we'll answer as many as we can. We'll publish a selection of answers every weekday on our website, and we're also putting some of your questions to the experts on the air during The National and on News Network.  

So far, we've received more than 30,000 emails from all corners of the country. Your questions have surprised us, stumped us and got us thinking.

Will herd immunity save us from COVID-19?

We are receiving a lot of questions about herd immunity, including an email from Suzanne K. who wants to know: How and when does herd immunity evolve? 

By definition, herd immunity evolves when a sufficient amount of the population becomes immune to a disease. When it comes to COVID-19, herd immunity means the virus would not be able to spread on its own, according to Erin Strumpf, a health economics expert at McGill University. 

"It's not prevention of a disease, per se, but it's prevention of an epidemic," she says.

Most experts suggest herd immunity cannot be achieved safely without a vaccine, because seniors and other vulnerable populations with suppressed immune systems would be at risk, and hospitals would be overwhelmed. 

Dr. Allison McGreer, infectious diseases specialist at Mount Sinai Hospital in Toronto, says herd immunity without a vaccine is "theoretically possible" if everyone, or almost everyone, who becomes infected develops antibodies that will protect them for life. 

While that might happen, "we don't know that [yet]," said McGreer. 

"It would just be foolish to count on it, which is why we're working on vaccines." 

WATCH | Dr. Allison McGeer, an infectious diseases specialist, answer audience questions on The National:

Could herd immunity to COVID-19 be as effective as a vaccine?

1 year ago
An infectious disease specialist answers your questions about COVID-19, including whether herd immunity could eventually be as effective as a vaccine. 1:44

British Prime Minister Boris Johnson rolled back the U.K.'s herd immunity strategy on March 16, just four days after it was implemented. Johnson later tested positive for COVID-19 and was admitted into intensive care. He has since been released.

You can read more about the debate around herd immunity and opening up schools in Quebec here.

How do I practise physical distancing during Ramadan?

Thanks to Aslam K. for this question. The month of Ramadan will look very different this year. This is the time when Muslims go without food or drink from sunrise to sunset every day, then gather to break their fast and pray together.

According to the Canada Council of Imams, mosques in Canada are taking their lead from health officials and their provincial governments, and will remain closed during Ramadan. 

Evening prayers during the month of Ramadan, which starts April 23, will be cancelled. Muslims will be asked to pray at home instead, said Abdul Hai Patel, the council's director of inter-faith relations.

Not having the community aspect of Ramadan this year "is going to be challenging," said Cindy Jadayel, a member of Ottawa's Masjid ar-Rahmah or Mosque of Mercy.

"We have to work harder this year to have families happier in the home because we can't go out and celebrate with others."

"With the pandemic this year, it seems different," said Riyaz Khawaja, president of the Hussaini Association of Calgary, the main Shia Islamic organization in the city.

"Congregation prayers and eating together, that part we'll be missing, but it's going to be better to observe ourselves and be more spiritual in these hard times," he said.

Khawaja says people will still be live-streaming prayers and sermons, donating to food banks, checking on neighbours and making financial donations during Ramadan and looking to help wherever it's needed.

He says Ramadan has always been about reflecting on those less fortunate.

Can you sterilize a cloth mask by ironing it?

We're still receiving lots of questions about masks, including this one from Janet S., who is wondering whether ironing her homemade mask will be enough to sterilize it. 

The short answer is no. Ironing your cloth mask will not work.

McGeer says that you can destroy some of the virus by heating it up, but it's not enough to effectively sterilize the mask. 

"Sterilizing requires a certain time, usually at least 10 minutes above a certain temperature like 65-70 degrees Centigrade, which you can't get from ironing," she says. 

Instead, Health Canada recommends laundering it on a hot cycle and drying thoroughly. 

"When you wash it, just the soap and water in the washing machine will remove the COVID-19," says McGeer.

But what about other masks, such as disposable paper surgical masks, and coveted N95 masks, which are used in both health-care and construction settings?

Disposable masks are not designed to be reused, and N95 masks also have a limited shelf life. 

That said, PPE shortages are forcing some health care facilities to experiment with safely decontaminating and reusing disposable masks. For instance, some hospitals are using UV light and pressurized sterilization machines called autoclaves to clean masks, but these methods cannot be safely replicated at home. 

With the warmer weather arriving, will wearing open-toed shoes be an issue? 

As the weather warms up, people like Eydie are wondering whether open-toed shoes could be an issue in terms of transmitting COVID-19. 

Open-toed shoes are okay, according to Dr. Lynora Saxinger, an infectious disease physician at the University of Alberta.

"Even if you had possibly an infectious virus on a shoe, in order to be infected you'd have to handle the shoe and then touch your face, nose or mouth or inhale the virus from the shoe," she says.

We've also received a number of questions about whether the virus can persist on footwear or on the ground. 

Dr. Peter Lin, a CBC News medical contributor and family physician, says while there is a small risk of the virus ending up on shoes from surfaces at grocery stores or other shops, the risk of contracting COVID off your shoes is low.

"The virus needs to get to your lungs, so [it's] very low risk that you will get the virus into your lungs [from your shoes]. When you get home don't walk around your place with your outside shoes, just leave them on a mat by the door.  No need to scrub down. Over a few days the virus breaks down on its own," he says. 

So while the risk transmitting COVID-19 from your shoes to you is low, you can minimize it altogether by keeping a shoe-free household for now. 

Read more on how to properly disinfect your home here.

Thursday we answered questions about pool protocol to blood donations. Read here.

Keep your questions coming by emailing us at


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