Why You Need to Wear a Mask Even After Getting the COVID-19 Vaccine

Chief Medical Epidemiologist Mini Kamboj

Chief Medical Epidemiologist Mini Kamboj

If you’ve been vaccinated against COVID-19, you might think you don’t need to wear a mask or practice social distancing any longer. That’s not true. Here’s why it’s so important to keep taking steps to protect yourself and others from COVID-19.

Your body needs time for the vaccine’s protection to kick in.

Vaccines work by triggering the immune system to make antibodies and mobilize certain cells to be ready to fight a virus like COVID-19. But this does not happen right away. A recent study published in the New England Journal of Medicine showed that protection from the Pfizer-BioNTech vaccine does not begin until 12 days after the first of the two shots. In other words, it takes some time for the army of immune cells to get into proper formation.

“It is hard to measure effectiveness precisely during the interim stage,” says MSK’s Chief Medical Epidemiologist, Mini Kamboj. In the study, the Pfizer vaccine did not achieve its full 95% effectiveness until about a week after the second shot. The Moderna vaccine, shown to be 94% effective, has a similar delay after the second dose before it offers maximum protection. In the Johnson & Johnson/Janssen trial, there were no cases of death or hospitalization 28 days after vaccination.

“With any of the vaccines, it’s very important to get both shots — and it takes time for the vaccine to reach full effectiveness,” Dr. Kamboj says. “You should continue being extra careful even after you have been fully vaccinated.”

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Despite getting both vaccine doses, you might still be contagious to others.

The clinical trials testing the two vaccines looked only at whether they protected people from getting sick from COVID-19 – not whether the vaccines stopped people from spreading the virus. This was because scientists wanted to create a safe and effective vaccine as quickly as possible. There hasn’t been time yet to study other things — like how long protection lasts or whether a vaccinated person could still pass the COVID-19 virus on to others. So the bottom line is: no one knows yet.

It’s possible you could get vaccinated and then become infected with COVID-19 but develop no symptoms. If your immune system does not completely wipe out the virus, there’s a chance you could still spread the virus to others.

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The vaccines effectively prevent people from getting sick from COVID-19, but we need to wait for researchers to continue studying people who have been vaccinated before we know if they could still transmit the virus.

Until these questions are answered, it’s important to continue taking precautions. They include avoiding crowds, washing your hands often, and staying at least six feet apart from people who don’t live in your household.

Yes, you must also wear a mask.  “No vaccine is 100% effective, so it’s feasible to still get COVID-19 after being vaccinated,” Dr. Kamboj says. “We know a mask protects you from infection, so it’s important to keep using them for your own safety and for those around you.”

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The COVID-19 threat won’t diminish until we have herd immunity — which will take time.

You might be thinking, “Fine, I’ll keep wearing a mask for now, but when can I stop? Will we ever be able to go back to the way it used to be?”

This kind of frustration is understandable, but COVID-19 is as dangerous as ever. We need to maintain safe practices until more people have immunity and the likelihood of the virus circulating is very low. This will happen only after a large percentage of the public is vaccinated or has recovered from a COVID-19 infection. It’s hard to determine what percentage is necessary for this so-called herd immunity, but many experts think it will be around 70%.

Herd immunity could take months or even years.  Many experts think some restrictions could begin to be eased by this fall, although it is too early to know for sure. 

“The speed with which these vaccines were developed — with more soon on the way — has been incredible,” Dr. Kamboj says. “The difficult scientific challenge has been met. Now the hard part is vaccinating as many people as possible. We must continue doing the other simple things we know will work until we all are safe.”


March 2, 2021


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