Covid vaccines, while highly resistant to hospitalization and death, offer little protection against the long Covid, according to a study published Wednesday in the journal Nature Medicine.
The results are disappointing, even surprising, for researchers who once hoped that vaccination could significantly reduce the risk of long Covid.
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Compared to an unvaccinated individual, the risk of long Covid in a fully vaccinated individual was only reduced by about 15%, according to the study.
“Vaccines are miraculous for doing what they were designed to do” — that is, preventing hospitalization and death, said Dr. Ziyad Al-Aly, a clinical epidemiologist at the University of Washington in St. Louis and lead author of the study. But they “offer very modest protection against the long Covid,” he said.
Covid vaccines were developed at the start of the pandemic, long before doctors, scientists and patients knew of the existence of the long Covid. They were never designed to protect against that, said Al-Aly, who is also chief of research at the VA St. Louis Health Care System. “We need to revisit them now that we know the virus can also have long-term consequences.”
Dr. Greg Vanichkachorn, director of the Mayo Clinic’s Covid Activity Rehabilitation Program in Rochester, Minnesota, who was not involved in the new study, said the results weren’t “too surprising.”
“We know that the majority of people who have had Covid for a long time haven’t had serious infections,” he said.
The study looked at national health care data from the US Department of Veterans Affairs and included the medical records of nearly 34,000 vaccinated people who had breakthrough Covid infections and more than 113,000 who did not. were not vaccinated when infected with Covid from January 2021 to October 2021. People were considered fully vaccinated if they had received two doses of the Pfizer-BioNTech or Moderna vaccine or a single dose of the Johnson & Johnson vaccine.
Researchers followed six months after infection to see if patients had persistent symptoms. While protection against long Covid in general was relatively weak, vaccines were more effective in preventing some of the most life-threatening long Covid symptoms: vaccination reduced the risk of lung disorders by almost 50% and blood clotting by 56%, compared to those who were not vaccinated.
Al-Aly noted that a breakthrough case does not mean a person will develop long Covid – only around 10% of breakthrough cases will lead to the disease – but with so many people infected, it still translates to a large number of people. .
The data did not show whether a person had been boosted, but Al-Aly said he does not expect boosting to make much of a difference in terms of vaccines protecting against long Covid, or variants like the omicron.
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Vanichkachorn agreed. “Unfortunately, I don’t think the boost will do much to prevent Covid for long with the vaccine,” he said. “We have many patients with breakthrough infections who are as vaccinated as possible. We also didn’t see much difference between variants with long Covid symptoms.
That’s not to say vaccines aren’t an important tool in the fight against the pandemic, experts say.
Boosters, in particular, offer the best protection against severe acute Covid and reduce the risk of complications, said Dr. Jason Maley, director of the COVID-19 Critical Illness and Survival Program at Beth Israel Deaconess Medical Center in Boston. .
But for a long time Covid, they are not necessarily the solution. “I don’t believe that vaccination is the key to eradicating the long Covid,” Al-Aly said. “We really need to think about additional layers to protect ourselves from the long-term consequences of this virus.”
New approaches to prevent the long Covid
Covid cases are rising again in the United States, driven now by an omicron subvariant called BA.2.12.1, according to the Centers for Disease Control and Prevention. Despite this, public health measures such as masking and social distancing have largely disappeared.
Al-Aly said he did not blame people for this.
“It’s not pragmatic to tell people to mask up for the next 10 years,” he said. But it underscores the need to improve vaccines and treatments in a way that could offer protection against the long Covid.
“Now that we have lifted all these other public health measures, vaccines are really the only layer of protection we have,” Al-Aly said. “This makes the question of what other means of prevention or treatment might be available even more urgent. Can we modify these original vaccines to also treat the long Covid, or do we also need intranasal vaccines or other therapies in addition? »
Intranasal vaccines, for example, could potentially prevent transmission better than current vaccines, but this is an area that needs to be studied, he said.
Maley, who also was not involved in the study, said growing research suggests that one of the main risk factors for long Covid is the level of virus in the body during the acute infection. This suggests that early treatment with therapies, including antivirals, could help prevent long Covid by keeping those virus levels low.
“Currently, antivirals are approved for emergency use authorization for patients at high risk of severe Covid-19, typically older adults or people with compromised immune systems,” said Maley. There is also interest, he said, in studying whether antiviral treatments could benefit long Covid patients.
Al-Aly and Vanichkachorn agreed that more research is needed on the long Covid. “We need continued research specifically on long Covid so that specific therapies can be developed,” Vanichkachorn said.
But right now, he said, “the best way to not have Covid long is to not get Covid”.
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