Coronavirus (Image provided by U.S. Centers for Disease Control and Prevention)

SARANAC LAKE — Some people get COVID-19 and have mild symptoms, or none. Others catch the virus and end up hospitalized, or dead. What determines how it will go? Experts say one factor is how much of the virus one has in one’s body.

Another is the strength of each person’s immune system.

Dr. Diana Christensen, an infectious disease expert at Adirondack Health in Saranac Lake, shared some insight on Wednesday into research on the coronavirus that sheds light on why some people may experience more severe COVID-19 symptoms than others. It’s not so much about the length of time a person is exposed to another person who is positive, but a combination of other factors.

So far, research seems to suggest that those with a higher viral load — basically a high amount of the virus in their bloodstream — may experience a worse outcome.

With any infectious virus, Christensen said that, in general, the more harmful the virus is, and the weaker a person’s immune system is, the more likely it is that that person will develop a more severe disease.

In the case of SARS-CoV-2, the official name of the new coronavirus, it appears that people with a higher viral load may have a worse outcome, according to Christensen.

“We can imply that the longer the exposure to a person infected with high viral load, the higher the chances for that person to transmit the virus and infect another person,” she said. “As I mentioned, symptoms and outcomes will depend not only on the amount of virus (viral load), but also on the relative health or weakness of an individual’s immune system.”

A study based on research from contact tracing in Spain, published in The Lancet, an infectious disease medical journal, shows that there is an association between a person’s viral load, how many others that person may infect, and how serious those other infections may be.

The coronavirus is spread through respiratory droplets and particles in the air. The higher a person’s viral load, the more virus there is to spread by coughing or breathing, Vox reported this week. And those who are infected by a person with a higher viral load are more likely to get sicker.

That’s where the vaccines come in. In the case of the Pfizer vaccine, according to an observational study based on data from Israel, those who are vaccinated will have a lower viral load if they later get infected. Thus, vaccinated people would be less likely to infect others, Vox reported. Those who are infected with the virus by a person who is vaccinated would then likely experience a better outcome.

A study from the United Kingdom, also published in The Lancet, shows that after an adult is fully vaccinated with the Pfizer vaccine, that person is effectively protected from both symptomatic and asymptomatic infection. The chances of a fully vaccinated adult developing an infection that can be transferred to others was cut down by 86%, the study found.

These studies are both new, and based on data that’s freshly culled. There are multiple different coronavirus variants, with different characteristics. Studies have shown the various approved vaccines to be more effective against some of these variants than other variants. It typically takes scientists and medical professionals years to fully understand a vaccine and its impact on people with different medical situations.

Much is still unknown about the coronavirus and the disease it causes, COVID-19. As more research is conducted, public health officials continue to stress the importance of taking safety precautions — wearing a mask, social distancing, limiting contact with people outside your immediate circle — even after vaccination.

As of Feb. 19, Essex County has allowed fully vaccinated people to not quarantine as long as they don’t have symptoms and can prove that they’ve received a second dose within 90 days of the exposure. But in a news release announcing this new guidance, Public Health Director Linda Beers asked residents to “continue to protect themselves and others.”

“We are still learning about the virus that causes COVID-19,” Beers said. “The vaccines approved to prevent the disease are new as well, and while they have demonstrated great success at preventing severe and symptomatic COVID-19, we just don’t know yet how long that protection lasts or how much the vaccines reduce transmission to others.”

Beers noted that there are unknowns about how effective the vaccines are against emerging variants of the coronavirus.

“Until we know more, we are asking all Essex County residents and visitors into our region, fully vaccinated or not, continue to protect themselves and others by wearing a mask, staying at least 6 feet away from others, avoiding crowds and poorly ventilated spaces, covering coughs and sneezes, and washing hands often,” she said.