Here's what we know about the effectiveness of vaccines for variants of concerns, notably the delta variant, first identified in India and now responsible for more than 20% of new U.S. cases.

There are some side effects that are pretty common: sore arm, headache, fatigue, fever. But people are saying they've got other unusual reactions. Is it the vaccine — or something else?

So, you've successfully scored a vaccine — or at least an appointment. Congrats! That's amazing news, seriously! Now what about those side effects? And do you have to keep up that double masking?

We ponder your pandemic questions. This week's topics: vaccine cards (including whether to laminate or not), group singing sessions and CBD products.

A reader wants to know about smoking's impact on the vaccine but didn't specify cigarettes, e-cigs ... or marijuana. So we'll discuss all three. Also: A refresher in painkiller/vaccine interaction.

Double masking earns praise as a way to keep safe from more contagious variants. Are there other mask hacks? And vaccines are prompting some queries.

Many of the coronavirus vaccines like it cold. Really cold. Sub-zero cold. Why is this the case? And how is the world handling this frigid requirement?

Are there issues with having a mammogram right after a vaccine? Is there a list of vaccine ingredients — some people say they're scary. Also: My pooch loves to sniff discarded masks. Should I worry?

Readers are asking about vaccine protocols, the safest way to take off a mask, whether it's risky to engage in therapeutic cuddling sessions with goats.

There are N95s, reserved for health workers. There are KN95s, which you can buy easily — except that quality may vary. And now South Korea's KF94 masks are getting a lot of buzz.

Plus: Can the virus make me sick many years later, like the chickenpox virus does?

States are closing down playgrounds again as case counts rise. Is that a good idea? Also: What's the deal with masks and outdoor exercise?

Answers to your COVID-19 questions about how to handle Halloween trick-or-treaters, whether it's safe to eat in a restaurant's outdoor bubble and whether you can be infected through your ear canal.

This week our readers have lots of ... interesting ... queries involving opening windows during winter in North Dakota, trying not to breathe during a micro-encounter and spraying a mask with ... oil?

Temperature scans are becoming commonplace around the world — at political events, at doctors' offices, at airports and more. Do they provide useful info to help reduce the spread of COVID-19?

Before COVID-19 came along, the world wasn't so great at counting deaths and understanding why people die. But the virus has propelled countries to ramp up their efforts.

Mass transportation ridership plummeted when COVID-19 struck. Now people are beginning to return. What are the risks they face — and how can they reduce them?

A study released this week points to two passengers infected on a four-hour-plus flight. But there hasn't been a lot of documentation of transmission on planes. So how risky is flying?

Experts look into a new study that claims wearing a neck gaiter may be worse than no mask at all. And they discuss other face coverings such as goggles and plastic face shields.

The matter of masks on planes has led to some contentious moments — and serious consequences. Is it legal to ban a passenger from flying for violating a mask mandate?