Understanding the Risk of Coronavirus Breakthrough Cases

What do you need to know about the risks of becoming ill with COVID-19 if you’ve been vaccinated? Does your age and overall health affect your risk of getting what’s commonly known as a “breakthrough” infection?

To understand your risks of becoming ill with a breakthrough infection — meaning an infection of individuals who have been fully vaccinated — it’s helpful to know the context of where the U.S. is in fighting the pandemic.

Nine months after the Food and Drug Administration administered its first emergency use authorization for a COVID-19 vaccine, a little more than 55% of the U.S. population is vaccinated against the deadly novel coronavirus, according to the Centers for Disease Control and Prevention.

At this point, virtually all of the patients who are hospitalized with COVID-19 — about 99% — are people who are unvaccinated, according to the CDC.

“The vaccines we have (Pfizer, Moderna and Johnson & Johnson) are exceptionally effective in preventing people from getting infected or becoming severely ill, requiring hospitalization and death,” says Dr. Kristin Englund, vice chairman of infectious disease at Cleveland Clinic.

[See: Fear, Courage, Grit: Meet More Than 50 ‘Hospital Heroes’ in Pictures.]

Low Rate of Serious Breakthrough Cases

A study published in Lancet Infectious Diseases in September 2021 notes that as of Aug. 30, the CDC reported 12,908 “patients with breakthrough infections who were hospitalized or had died.” That represents less than 0.008% of all fully vaccinated individuals in the U.S.

Using data from the Yale New Haven Health System, researchers in the Lancet study found that 172 (18%) of 969 patients who’d been hospitalized had gotten at least one dose of a COVID-19 vaccine at the time they were admitted. Overall, 54 who were hospitalized were fully vaccinated. These patients were considered to have breakthrough infections.

Of the 54 vaccinated patients who required hospitalization, researchers wrote that 14, or 26%, had “severe to critical illness.” Four of these patients required intensive care, one needed mechanical ventilation and three died, according to the study.

[See: 14 Myths and Misconceptions About the Flu Vaccine.]

Risk Factors for COVID Breakthrough Cases

The median age of the 14 patients with severe illness in the Lancet study was more than 80 years. And many had preexisting comorbidities, which included:

Being overweight.

— Cardiovascular disease.

— Lung disease.

— Type 2 diabetes.

“We see very small numbers of patients being admitted (to a hospital) who are fully vaccinated,” Englund says. “The threat of breakthrough infections that lead to hospitalizations is still quite low.”

The low rate of serious disease from breakthrough infections is important to keep in mind, says Dr. Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children’s Hospital.

The symptoms for breakthrough infections typically last a few days and include:

— Chills.

— Fatigue.

— Fever.

— Coughing.

— Sore throat.

— Shortness of breath.

[See: Ways to Boost Your Immune System.]

Vaccines Remain Effective

Each of the three vaccines administered in the U.S. are effective in preventing hospitalization among U.S. adults without an immunocompromised condition, according to research published in September 2021 by the CDC.

Regarding people who are immunocompromised, the CDC issued a statement in early September 2021 that says that emerging data “have demonstrated that immunocompromised people who have low or no protection following two doses of mRNA COVID-19 vaccines (Pfizer and Moderna) may have an improved response after an additional dose of the same vaccine.”

There’s not enough data to determine whether immunocompromised individuals who got the one-dose Johnson & Johnson COVID-19 vaccine may also have an improved antibody response with an additional dose of that vaccine, the statement says. Studies are underway to determine whether getting a booster shot would be advisable for immunocompromised people who got the J&J vaccine.

The CDC study showed the vaccines had these levels of effectiveness in preventing hospitalization:

— Moderna, 93%.

— Pfizer, 88%.

— Johnson & Johnson, 71%.

The Dangerous Delta Variant

At this point in the pandemic, almost every person who is being infected and hospitalized in the U.S. — whether they are vaccinated or not — are contracting COVID-19 from the Delta variant, which is much more transmissible than the original coronavirus strain. The Delta variant accounts for 99% of all infections and hospitalizations, breakthrough or not, Englund says.

Vaccine Boosters Shots

The data showing that age is a risk factor suggests the need for booster shots, particularly for people who are age 65 or older and individuals with underlying health conditions, Blumberg says.

Recently, federal health authorities endorsed Pfizer booster shots for certain groups of people in high-risk groups or occupations.

The CDC says people in these groups should get a Pfizer booster at least six months after they got the second shot of their initial vaccinations:

— People age 65 and older and residents of long-term care settings.

— Individuals age 50 to 64 with underlying medical conditions, including cancer, diabetes, chronic lung disease, chronic kidney disease and heart disease.

People in these groups may receive a Pfizer booster shot at least six months after their second primary vaccination:

— People between the ages of 18 and 49 with underlying medical conditions.

— Individuals between the ages of 18 and 64 who are at increased risk for COVID-19 exposure and transmission because of their occupational or institutional setting. This could people who work in hospitals, for example.

In weighing the risks of breakthrough infections, overall, research suggests that vaccines remain an effective safeguard, says Dr. Dushyantha T. Jayaweera, a professor of medicine at the Miller School of Medicine in Miami.

“Vaccines do not do not guarantee herd immunity, but will stop mortality and morbidity,” he says.

More from U.S. News

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Understanding the Risk of Coronavirus Breakthrough Cases originally appeared on usnews.com

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