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Long COVID can cause persistent COVID-19 symptoms including loss of smell, fatigue, mood changes, and brain fog in addition to disorders of the heart, kidneys, and lungs. These symptoms emerge or continue at least one month after a SARS-CoV-2 infection.
It is estimated that 7.7 to 23 million Americans may have developed long COVID, a condition also called post-acute COVID or chronic COVID.
A study at the Washington University School of Medicine in St. Louis and the Veterans Affairs St. Louis Health Care System suggests that vaccination alone may not be enough to stop breakthrough COVID-19 infectionsTrusted Source and prevent long COVID.
Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University and lead author of the study, said:
“Vaccinations remain critically important in the fight against COVID-19 […] But vaccines seem to only provide modest protection against long COVID.”
The findings appear in Nature MedicineTrusted Source.
Filling the knowledge gap
Al-Aly and his co-authors set out to confirm whether breakthrough SARS-CoV-2 infection (BTI) can also lead to long COVID complications among vaccinated people between one to six months after infection.
They studied data on almost 34,000 people with BTI, based on the U.S. Department of Veterans Affairs’ national healthcare records. The data spanned from January to October 2021.
An individual was considered to have a BTI by having tested positive for SARS-CoV-2 at 14 days after having received one dose of the Johnson & Johnson/Janssen vaccine or two doses of the Pfizer BioNTech or Moderna vaccines.
The team compared this information with that of almost 5 million people from the same healthcare database who did not develop COVID-19 during the same period. Almost 5 million people made up this contemporary control group.
Higher mortality risk
In an interview with Medical News Today, Dr. Al-Aly explained that studying the control group helped ensure that the long COVID symptoms observed weren’t due to undetected, pre-existing conditions.
Compared to the control group, people who survived the first 30 days of a breakthrough infection were 1.75 times more likely to die than if they did not develop COVID-19.
Those in the BTI group also had a greater risk of developing at least one post-acute disorder.
However, results also confirmed that COVID-19 vaccines provide protection. When comparing BTI to unvaccinated individuals who had SARS-CoV-2 infections, the results indicated that COVID-19 vaccines can lower the risk of death by 34% and long COVID by 15%.
The study’s significance
The current study is among the first to assess the risks of breakthrough infections and long COVID on a large scale.
It also used data from the largest national integrated healthcare database in the U.S., the Department of Veterans Affairs.
The co-authors acknowledge a few limitations, though. The groups analyzed did not include people who may have had a SARS-CoV-2 infection but were not tested.
Most of the patients studied were older, white males. However, the data analyzed included participants from diverse age groups and races and included over 1.3 million female participants.
Understandably, the study did not consider Omicron variants that started spreading after the study period ended. According to Dr. Al-Aly, though, the vaccines work against all current variants.
Although data on booster shots were unavailable at the time of the research, Dr. Al-Aly told MNT that the team’s study is ongoing, and they are quite interested in exploring the role of boosters.
MNT also discussed this study with Dr. Margaret Liu, chair of the board of the International Society for Vaccines, who was not involved in the research.
Dr. Liu noted that the many unknowns and differing scientific perspectives make it challenging to interpret the data.
“One of the challenges for interpreting any data is that the strains circulating now clearly are different in terms of infectivity than are earlier strains—i.e., those circulating when published studies were done, just based on the speed with which new strains have made inroads, and the length of time needed for such studies and then publication,” she said.
Prevention beyond vaccines
MNT also discussed this study with Dr. Joseph A. Roche, an associate professor in health sciences at Wayne State University, who was also not involved in the research.
Dr. Roche agreed that vaccines do not replace other risk reduction methods for COVID-19. He pointed to a paper he authored which urges “continued nonpharmacological risk-reduction measures […] to complement vaccination efforts.”
In his research, he cited mathematical models which predicted that such measures should stay in place for a year, even after the population reaches ideal vaccination levels.
Dr. Roche also noted that his stance aligns with the World Health OrganizationTrusted Source’s “repeated warnings against premature abandonment of risk-reduction measures.”
Dr. Liu agreed.
“[…A] big reason that I and other physicians are still being so careful to still mask and to avoid as much as possible situations of exposure […] is that prevention of any COVID-19 infection is still the best strategy to avoid long-haul COVID. I also don’t want to be a vector for other people who may have higher risks,” she said.