Older adults are more susceptible to severe breakthrough COVID-19, studies show

What is a COVID-19 breakthrough case?

While breakthrough cases have become more common as the highly contagious delta variant spreads, the COVID-19 vaccines have still proven remarkably protective and effective against hospitalizations and deaths.

The death of 84-year-old former U.S. Secretary of State Colin Powell, who was fully vaccinated, has highlighted how older, immunized adults are still at risk for severe COVID-19 breakthrough infections.

The U.S. Centers for Disease Control and Prevention has said that vaccine breakthrough cases are expected as no vaccine is 100% effective. But health officials maintain that the COVID-19 vaccine is still the best protection against serious illness and death from a coronavirus infection.

According to the AARP, older adults are already susceptible to COVID-19 complications due to underlying health conditions, which affect about 80% of older Americans. Many also have a less robust immune system.

As of Oct. 12, the CDC has received reports of 31,895 breakthrough cases in the U.S. Of the 24,717 people who have been hospitalized — 16,509 people were 65 years and older. Of the 7,178 deaths — 6,104 people were 65 years and older.

CDC officials said multiple studies are underway to further understand breakthrough cases and specific contributing factors such as age, underlying medical conditions, brand of vaccine and COVID-19 variants.

A September 2021 study published in "The Lancet" also pointed out that older, vaccinated adults are more susceptible to severe COVID-19 breakthrough cases. Researchers studied breakthrough cases between March and July. They found among the most critical cases, the average age was 80 years old and tended to have pre-existing conditions such as obesity, cardiovascular or lung disease and type 2 diabetes.

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A September 2021 study published in the U.S. National Library of Medicine also found similar results, noting that "in persons with breakthrough SARS-CoV-2 infection, increasing age is associated with a higher risk of severe disease or death."

The AARP also pointed out that many older adults were the first to receive the COVID-19 vaccine and protection against the virus has waned as several studies suggested. Officials believe that could also play a part in the increased risk of severe breakthrough infections.

The CDC released two studies in September that signaled hints of waning protection for older adults. One examined COVID-19 hospitalizations in nine states over the summer and found protection for those 75 and older was 76% compared to 89% for all other adults. And in five Veterans Affairs Medical Centers, protection against COVID-19 hospitalizations was 95% among 18- to 64-year-olds compared to 80% among those 65 and older.

U.S. health officials have approved COVID-19 booster shots for certain groups, including older Americans.

Last month, Pfizer boosters began being offered to seniors and younger adults at high risk from COVID-19 because of poor health, jobs or living conditions — at least six months after their initial vaccination.

Last week, the U.S. Food and Drug Administration advisory panel recommended the same approach for half-dose Moderna boosters.

Johnson & Johnson is currently seeking approval of its booster shot from the FDA as well. U.S. health advisers cited concern that Americans who got the single-dose shot aren’t as protected as those given two-dose brands.

The vast majority of the 188 million Americans who are fully vaccinated against COVID-19 have received the Pfizer or Moderna options, while J&J recipients account for only about 15 million.

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Among people who stand to benefit from a booster, there are few risks, the CDC concluded. Serious side effects from the first two Pfizer doses are exceedingly rare, including heart inflammation that sometimes occurs in younger men. Data from Israel, which has given nearly 3 million people — mostly 60 and older — a third Pfizer dose, has uncovered no red flags.

President Joe Biden has said if you’re vaccinated, "You’re in good shape and we’re doing everything we can to keep it that way, which is where the booster comes in." The 78-year-old received his booster shot last month.

The Associated Press contributed to this report. This story was reported from Los Angeles.