Can breakthrough infections in vaccinated groups lead to long Covid? Here’s what scientists say

Breakthrough Covid-19 is unlikely to result in hospitalisation or death even though cases among the fully vaccinated are inevitable.

However, it is still unclear if the vaccinated can develop long Covid.

Long Covid refers to severe fatigue, headache, muscle pain, brain fog, and sleep problems that can remain for weeks or even months following the end of active infection. While there is no full-scale understanding of the syndrome, studies suggest between 10 per cent and 30 per cent of adults who are infected by the virus, including those with mild or no symptoms, may experience long Covid.

However, the majority of the data on long Covid has been collected from the unvaccinated population. There are no studies on the risk of long Covid in the fully vaccinated population.

While preliminary research suggests the possibility of breakthrough infections leading to symptoms that remain for weeks and months, it raises more questions than answers.

Dr. Zijian Chen, Medical Director at the New York based-Mount Sinai Health System’s Centre for Post-COVID Care, said there is not enough data. She told The New York Times that the population contracting the virus post vaccination is low right now, adding that there is no good tracking mechanism for such patients.

A recent study on health care workers in Israel offers an insight into the risk of long Covid following breakthrough infections. The study, published in the New England Journal of Medicine, found that 39 of 1,497 fully vaccinated healthcare workers in the country developed breakthrough infections. The study was conducted before the spread of the contagious Delta variant and the healthcare workers were believed to have contracted the virus following contact with an unvaccinated person.

While most of the patients with breakthrough infections had mild symptoms or were asymptomatic, seven of 36 workers tracked at six weeks had lingering symptoms. The symptoms of long Covid included persistent cough, weakness, fatigue, prolonged loss of smell, laboured breathing, and muscle pain.

However, the authors of the study warned against drawing too many conclusions. The sample size of seven patients is small and the research was mainly designed to study antibody levels in the infected, Dr. Gili Regev-Yochay, Director of Tel Aviv-based Sheba Medical Centre’s Infectious Disease Epidemiology Unit, told The New York Times.

Dr. Regev-Yochay said the research was not designed to carry out studies on the risk of long Covid following a breakthrough infection.

Despite that, with one in five healthcare workers with breakthrough infection still displaying symptoms after six weeks is an indication that breakthrough infections can lead to long Covid.

The U.S. Centers for Disease Control and Prevention (US CDC), which only tracks infections post-vaccination that result in either hospitalisation or death, further complicates the study. While it continues to research breakthrough infections, the lack of data on all breakthrough cases has frustrated patient advocacy groups and scientists.

Yale School of Medicine immunologist Akiko Iwasaki, who is conducting studies on long Covid, told The New York Times that it was frustrating not to have data at this time to know what happens to breakthrough cases.

Iwasaki said if mild breakthrough infections were indeed turning into long Covid, there is no grasp on that number.

Some experts have predicted that the surge in cases following the Delta variant’s spread would lead to more breakthrough infections in the coming months. Dr. Chen of Mount Sinai Health System said, however, that it would be months before patients who develop long Covid symptoms after breakthrough infections are enrolled for studies.

Athena Akrami, a University College London neuroscientist, said despite the shortage of data, getting vaccinated would reduce the risk infection and long Covid. Akrami collected and published data from 4,000 long Covid patients, having herself developed long Covid after contracting Covid-19 in March 2020.

According to Akrami, it’s simple math — if infections drop, the likelihood of long Covid will automatically go down.