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People wait in line for a COVID-19 vaccine. Wang Ying/Xinhua via Getty Images
  • A new study finds that vaccinated people who get a breakthrough case of COVID-19 have a 49 percent lower risk of developing long-haul COVID-19.
  • Symptoms of long-haul COVID-19 can last weeks to months or even longer. They include brain fog, fatigue, persistent loss of smell or taste, hair loss, and numbness.
  • Some people who had mild cases of COVID-19 still end up with symptoms of long-haul COVID-19. This new study finds breakthrough cases are less likely to lead to long-haul COVID-19.

COVID-19 can cause severe illness, sometimes leading to hospitalization and death. But even for people who had mild symptoms, some people have been left with long-term symptoms, now called long-haul COVID-19, or “long COVID.”

“Long COVID is the syndrome of persistent symptoms that develops after the virus that causes COVID has been cleared,” Thomas Gut, DO, associate chair of medicine and director of the Post-COVID Recovery Center at Staten Island University Hospital in New York, told Healthline.

Gut said symptoms can last weeks to months and include brain fog, fatigue, persistent loss of smell or taste, hair loss, and numbness.

With the rise of vaccinations, health experts have been trying to determine whether people who get breakthrough infections would be at the same risk of developing long-haul COVID-19 as unvaccinated people.

A new study published in the journal The Lancet Infectious Diseases on Sept. 1 finds vaccination not only reduces the risk of infection and severe symptoms, but significantly cuts the odds of experiencing long-term effects if you’re one of the few who experience a breakthrough infection.

Researchers analyzed data from more than 1.2 million adults in the United Kingdom who participated in the national COVID Symptom Study.

They evaluated reports from people who had been given at least one dose of Pfizer-BioNTech, Moderna, or AstraZeneca mRNA COVID-19 vaccine between December 2020 and July 2021.

Researchers included a control group of unvaccinated people for comparison.

According to the findings of 971,504 fully vaccinated people, only 0.2 percent went on to develop a breakthrough infection.

When this data was compared with reports from unvaccinated people who got COVID-19, it was found that breakthrough cases were associated with a 49 percent lower risk of symptoms lasting 4 weeks or more after infection.

“Recent reports suggest that some individuals remain with ongoing symptoms for at least a year after the infection,” said Dr. David Hirschwerk, an infectious disease specialist at Northwell Health in Manhasset, New York. “Some, of course, will have resolution earlier.”

According to the study, frailty was significantly associated with breakthrough infection in older adults after their first vaccine dose.

Two possible reasons researchers gave for this finding are that adults with frailty are often in long-term care facilities, where there’s increased risk of contracting respiratory illness, and that they have weakened immune systems due to older age.

“This increased risk might therefore reflect increased exposure: unlike non-frail older adults, frail older adults might require carer visits or attendance at health-care facilities,” the study authors wrote.

“It remains relatively uncommon,” Hirschwerk said. “But we are experiencing an uptick in breakthrough cases compared to several months ago.”

He confirmed that the Delta variant has drastically reduced vaccine effectiveness.

“The vaccines remain about 65 percent effective at preventing symptomatic COVID-19 infection — but previous estimates were around 90 percent,” he said.

According to Hirschwerk, the increase in breakthrough infections is likely a combination of the more infectious Delta variant, some degree of waning immunity in people vaccinated over 6 months ago, and diminished community mitigation to prevent transmission.

He emphasized that “we’re seeing an overall increased prevalence of COVID-19 right now,” which means there’s more exposure to the coronavirus for everyone.

According to the Centers for Disease Control and Prevention (CDC), COVID-19 vaccines, like all other vaccines, are not 100 percent effective at preventing infections.

However, the CDC points out that:

  • Fully vaccinated people with a breakthrough infection are less likely to develop serious illness than those who are unvaccinated and get COVID-19.
  • Even when fully vaccinated people develop symptoms, they tend to be less severe symptoms than experienced by unvaccinated people, reducing the risk of hospitalization or death.

Hirschwerk said it’s important for every eligible person to get vaccinated.

“There are so many important reasons,” he said. “But emerging data supports that vaccination can also reduce the likelihood of individuals developing long COVID if they develop breakthrough infection, compared to becoming infected while not vaccinated.”

Gut, who specializes in treating people with long-haul COVID-19, agrees that the best strategy to reduce the risk of all COVID-19 complications, “including long COVID syndrome and death,” remains vaccination.

Long-haul COVID-19 affects a significant number of people who recover from the disease. New research finds that vaccinated people who get a breakthrough infection have a 49 percent lower risk of developing long-term symptoms.

Experts say fully vaccinated people with a breakthrough infection are also less likely to develop serious illness or be hospitalized.

They also say that while there’s currently no treatment for long-haul COVID-19, vaccination is a prevention strategy for everyone.