Vaccination against SARS-CoV-2 lowers the risk of long COVID after infection by only about 15%, according to a study of more than 13 million people1. This is the largest cohort to date to determine how vaccines protect against the condition. However, it is unlikely that this will end the uncertainty.
Long CoVID — an illness that persists for several weeks or months after infection by SARS-CoV-2 — is difficult to study due to the variety of symptoms. It is difficult to determine how common it actually is. Some studies have suggested that it occurs in as many as 30% of people infected with the virus. A November study of approximately 4.5 million people who were treated at US Department of Veterans Affairs (VA), hospitals found that the overall number of cases was 7%. This is lower than the rate for those who were not hospitalized.
Another mystery is whether long COVID occurs less often after a breakthrough infection. This could be because vaccinated people are more likely to have the same symptoms as those who have not been vaccinated. In a 25 May study in Nature Medicine, nephrologist Ziyad Al-Aly at VA Saint Louis Health Care System in St Louis, Missouri, and his colleagues — the same team that authored the November study — looked at VA health records from January to December 2021, including those of about 34,000 vaccinated people who had breakthrough SARS-CoV-2 infections, 113,000 people who had been infected but not vaccinated and more than 13 million people who had not been infected.
Chinks in the armour
The researchers found that vaccination seemed to reduce the likelihood of long COVID in people who had been infected by only about 15%. This is in contrast to smaller studies that have shown much higher protection rates. It’s also a departure from another large study, which analysed self-reported data from 1.2 million UK smartphone users and found that two doses of a COVID-19 vaccine halved the risk of long COVID.
The latest study also examined the effects of SARS-CoV-2 on fatigue and brain fog in both vaccinated individuals and those who were not. The team found no difference between people who had been vaccinated versus those who hadn’t. Al-Aly states, “Those fingerprints are the same ones we see in people with breakthrough infections.”
There have been more than 83 million COVID-19 infections in the United States alone, he notes. He notes that even a small percentage of these turn into long COVIDs, which is a staggeringly large number of people who are affected by a mysterious disease.
The limited protection offered by vaccines means that removing restrictions such as social-distancing and mask mandates could put more people at risk, especially those with compromised immune systems. Al-Aly says, “We are literally solely dependent, now almost exclusively on the vaccine to defend us and the public.” “Now we’re saying it’s only going to protect you 15%. You are still vulnerable, and extremely so .”
” “Generally speaking, this is horrifying,” says David Putrino of Mount Sinai Health System in New York City, who studies long COVID. Although he praises the study for being difficult due to the quality and quantity of data, he also says that it is not limited in that it does not break down key factors such as the medical history of the participants. Putrino states that these are important questions to which we need answers. “We don’t have any really well-constructed studies .”
Another Omicron unknown
Steven Deeks is an HIV researcher at University of California, San Francisco. He points out that the study does not include data from people who were infected during the Omicron variant’s peak period. He says that there is no data to determine if Omicron causes long-term COVID. He says that the findings “apply to an epidemic that has dramatically changed”.
Deeks says that the results show the need to do more research on long COVID and accelerate the development of therapies. He says, “We don’t have a definition, a biomarker or an imaging test, a method, or a treatment.” “We only have questions .”
This article is reproduced with permission and was first published on May 25 2022.