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Why do some people get seriously sick with COVID-19 while others don’t?

Dr. Pinsky, Medical Director of Infection Control and Prevention at Edward Hospital shared in the Edward Elmhurst Healthy Driven Blog that one of the most baffling aspects of COVID-19, the illness caused by SARS-CoV-2, is how differently it seems to affect people.

One person may have mild symptoms and recover in just a few days while another person may have prolonged symptoms that lead to pneumonia, shortness of breath, and hospitalization. Some may not develop symptoms at all.

In each case, the virus can be transmitted two days prior to the onset of symptoms (pre-symptomatic) and up to 10 days after the onset of symptoms for those with mild symptoms. For those who don’t develop symptoms, the infectious period is shorter, but no more than 10 days. Those who have severe infections requiring hospitalization may be infectious for up to 20 days.

 

Risk factors for severe infection

The same spectrum of severity can occur at any age and within any risk group, even within the most vulnerable elderly populations. Those over age 65 compromise the majority of deaths due to COVID-19, but there is excess mortality due to COVID-19 in all adult age groups. Many more of all ages have survived with severe symptoms and suffer a prolonged and debilitating illness.

Severe infection is uncommon in children and young adults. Rare complications include multisystem inflammation in children and heart failure in young adults.

Severe COVID-19 infection typically manifests as a progressive pneumonia with trouble breathing and can affect adults of all ages. It is more common for those over age 50 and the risk rises each year after that.

Other risk factors for severe infection or death include obesity, diabetes mellitus, kidney disease, chronic lung and heart disease, and other conditions that impair immune function. African American and Hispanic groups have higher rates of underlying medical illness and have been disaproportionally affected by COVID-19.

While anyone who has mild COVID-19 infection can progress to severe infection, the risk is much higher for:

  • Adults over the age of 65
  • People with diabetes, obesity, or chronic kidney disease
  • People with a suppressed immune system
  • Adults over age 55 with heart or lung disease

Studies have shown that transfusion of monoclonal antibodies can reduce the chances of developing severe infection and hospitalization. Monoclonal antibodies have received an Emergency Use Authorization by the FDA for those with mild or moderate COVID-19 infection who have any of those risk factors.

Immunity to COVID-19

One of the reasons COVID-19 has caused so many severe infections, hospitalizations and death is that it is a new virus. After one year of SARS-CoV-2 (the virus that causes COVID-19) circulating through the population, most of us are still susceptible.

Fortunately, there are now vaccines that will get you to immunity without the health costs of getting infected. The Moderna and Pfizer-BioNTech vaccines are 94-95% protective against symptomatic infection and nearly completely protective against severe infection.

The more people who are vaccinated, the fewer will be susceptible to infection, and the fewer that can transmit the virus to others. The full level of protection isn’t achieved until two weeks after the second dose. It is important to continue to wear masks along with all the other mitigation measures until enough of the population is vaccinated to get herd immunity.

For the latest updates on the COVID-19 vaccine, please check EEHealth.org/coronavirus/vaccine.

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