Coronavirus

Covid-19 event risk assessment: Coronavirus experts give health guidance

5 questions & answers

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It's been more than a year since Covid-19 emerged. With it came the now-familiar mental math we never wanted to perform: Is it safe to visit my parents? Should I risk going to a restaurant?

The situation is made more complicated by changing variables. Some are hopeful, like the roll-out of Covid-19 vaccines. Others less so, like the emergence of new virus variants. What is undeniable, however, is that we're in a different world than the first time we heard the phrase 'social distancing' in March 2020. It's O.K. to feel confused.

Experts do have advice for navigating coronavirus in 2021. Read on to know how to evaluate the risk of any event, both before vaccination and after vaccination.

Evaluating risk before being vaccinated:

How can you assess Covid-19 event risks?

At this point in the pandemic, we know certain factors put one at higher risk for infection with SARS-CoV-2, the virus that causes Covid-19. These include, but may not be limited to:

To help navigate the world, there are Covid-19 event risk assessment planning tools you can use. One is a dashboard, created by members of the Georgia Institute of Technology.

It provides a clear estimate of risk, depending on the location of an event and its size.

An example of the Covid-19 event risk assessment planner. This model calculates the risk for a 150 person wedding in California.Joshua Weitz et. al.

Many risk assessments assume personal risk is directly related to the Covid-19 prevalence in the area, Stefan Baral, a physician epidemiologist and an associate professor at Johns Hopkins School of Public Health, tells Inverse.

Baral says this is part of the question, but ultimately, he believes "one's living and working conditions will define your risks for Covid-19 far more than the general prevalence in the community."

If people in your network are essential workers or live with people who are essential workers, then your network risk is high, Baral explains. Pre-existing inequities, in turn, have resulted in increased risk for certain communities with a higher proportion of people who work in essential industries, and not others.

"We should not let the question of social gatherings take our eyes off structural racism, which is such a critical driver of disparities in Covid-19," Baral says.

Covid-19 is capable of causing prolonged illness, even among young people without pre-existing conditions. But certain individuals are at greater risk of developing severe Covid-19 if infected. The risk of severe disease increases with age and preexisting medical conditions. Studies also suggest men may be more likely to develop severe Covid-19, compared to women.

Should new variants change our behavior?

Emerging variants of the coronavirus introduce new elements to take into account when making choices about Covid-19 risk. Three variants under surveillance by the U.S. Centers for Disease Control and Prevention (C.D.C.) appear to spread more easily and more rapidly than the original strain, although these data are still emerging.

Denis Nash is a professor of epidemiology and the executive director of the City University of New York's Institute for Implementation Science in Population Health. He tells Inverse the variants may accelerate the spread of Covid-19. But ultimately, the emergence of variants should not change individual behavior, because the precautions are not different for one variant over another, he says.

Safe Covid-19 behavior is safe Covid-19 behavior.

"We're learning a lot about the importance of more protective masks like K95s and double-masking," Nash says.

"I think it all makes total sense — not because there's a variant, but because these masks are better at preventing all Covid-19 spread."

What the variants should inspire is a greater sense of urgency for vaccine roll-out and coverage, Nash says. "There's room to change behaviors safely," Nash says, but he cautions against people letting their guard down, even though vaccinations have now begun.

"We need to keep our eye on the bigger prize of limiting transmission, as long as we can, until we can get vaccine coverage to be high," Nash says.

Is it dangerous to eat out during Covid-19?

Covid-19 cases are trending downward in the United States, but they still remain high. Some states are loosening indoor dining restrictions in an attempt to support business and boost the economy. New York, for example, allowed indoor dining at 25-percent capacity starting Friday.

It's a controversial step. Some critics argue the more ethical decision is to provide economic support to restaurant workers. Public health experts, too, are largely aligned: Stick to the outdoors, delivery, and take-out.

"I would not eat indoors at a restaurant," Nash says.

"It makes no sense to me why you would make a decision to open indoor dining in a place where there are high levels of community spread and a high prevalence of virus in the community," he says.

"We know it contributes to community spread, we know it contributes to super-spreading, and we know it puts restaurant workers at higher risk."

For his part, Baral says outdoors is safer than indoors.

Evaluating risk after being vaccinated:

Can you spread Covid-19 with a vaccine?

In short, it's complicated. On Thursday, the C.D.C. announced fully vaccinated people who received both doses within the last three months do not need to quarantine if they have been exposed to Covid-19 and if they remain asymptomatic.

The C.D.C. states:

Although the risk of SARS-CoV-2 transmission from vaccinated persons to others is still uncertain, vaccination has been demonstrated to prevent symptomatic COVID-19; symptomatic and pre-symptomatic transmission is thought to have a greater role in transmission than purely asymptomatic transmission. Additionally, individual and societal benefits of avoiding unnecessary quarantine may outweigh the potential but unknown risk of transmission, and facilitate the direction of public health resources to persons at highest risk for transmitting SARS-CoV-2 to others.

Preliminary research does suggest people who become infected, but are fully vaccinated, develop a lower viral load. This means they are less likely to transmit Covid-19 to others. For example, a preprint study (not yet peer-reviewed) released in February found the Pfizer vaccine caused a 4-fold reduction in viral load if a person became infected within 12 to 28 days after the first dose of vaccine.

"[A reduction in viral load] would be consistent with what we have known about historical vaccines — including those vaccines that prevent severity of infection even if they don't always prevent infection," Baral tells Inverse.

But this study is a preprint, so the research needs to go through peer review before public-health officials can be confident about the results, Baral says.

There is no good answer to the question of whether vaccinated people can become infected and spread Covid-19 to others, William Schaffner tells Inverse. Shaffner is a professor in the Department of Health Policy and the Division of Infectious Diseases at the Vanderbilt University School of Medicine.

The vaccines' clinical trials were designed to show whether the vaccines prevented people from getting sick, Schaffner says. They were not designed to show whether they prevented people from getting infected.

"It does look as though the vaccines substantially reduce infection and hence transmission, but we're not there yet," Schaffner says.

"Until we can say that with some assurance, let's all keep wearing the masks. Not only for ourselves, but for others."

Can you see friends and family after getting vaccinated?

When deciding how to behave post-vaccination, it's important to keep four factors in mind:

  • The uncertainty over whether vaccinated people can spread Covid-19.
  • How at-risk you are if you do become infected. Both the Pfizer and Moderna vaccines are approximately 95 percent effective at preventing severe cases of Covid-19. They greatly reduce the chance of hospitalization or death, but it's currently unclear whether or not infected and vaccinated people develop symptoms.
  • How at-risk the people you are seeing may be of severe disease if they become infected.
  • The risk-taking behavior of the people you are meeting.

"When going out in the world, generally, vaccinated people should continue their safety behaviors," Schaffner says.

"A huge portion of the population is still unvaccinated. Don't look for reasons to not wear a mask — we're not there yet."

But there can be some nuance when deciding whether or not to meet indoors with friends and family, he says.

Say, for example, you are a vaccinated grandparent who wants to see your adult grandchildren. The longer the visit, the larger the group, and each person's behavior in the lead-up to the meeting influence the ultimate risk.

"The vaccination doesn't make your grandparents wear a suit of armor."

With more widespread vaccination, and reasonable degrees of safety, Schaffner does think we may soon be able to participate in more social events. But it's better to be more cautious than carefree.

"The vaccination doesn't make your grandparents wear a suit of armor," Schaffner says.

If you are vaccinated, it doesn't mean you should be around people who are not vaccinated — unless it's a clear situation where transmission is not going to happen, Nash says.

"It's not a fun answer, right?" Nash says. "I think things are largely the same."

What works for one person doesn't necessarily work for another — Baral argues harm reduction has less to do with deciding certain behaviors are okay, and more to do with finding the safest choice possible, dependent on a person's circumstances.

Consider Schaffner's example: He and his wife are now vaccinated. Prior to vaccination, the couple were in a pod with another family. That family is not vaccinated, so they plan on continuing with all the rules they had set before. But, if he was interacting with other vaccinated people, he might consider letting his guard down — if they also continued careful behavior when interacting with the rest of the world.

Ultimately, no matter what Covid-19 category you're in, don't forget your mask.

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