Recovered COVID patients may have immune memory for up to 8 months
In a US study published today in Science, researchers detected immune memory to SARS-CoV-2 across all immune cell types studied for as long as 8 months after patients became ill with COVID-19.
In the study, a team led by researchers from the La Jolla Institute for Immunology in California analyzed levels of antibodies and other cells involved in immune response to the novel coronavirus in 254 specimens from 188 recovered adult COVID-19 patients, including 43 samples taken 6 months or more after infection.
Recruited from sites across the United States, study participants had a range of COVID-19 illness severity, from asymptomatic to severe, although most had mild cases. Of all participants, 93% were never hospitalized; of the 7% who were hospitalized, some required intensive care.
Concentrations of anti-spike protein immunoglobulin G (IgG), anti-nucleocapsid IgG, RBD IgG, and PSV neutralizing antibodies decayed slightly but remained relatively stable for more than 6 months, and spike-specific B cells were more abundant at 6 months than at 1 month after illness onset.
Concentrations of SARS-CoV-2–specific CD4+ and CD8+ T cells, which have been linked to more mild disease, waned to half their original concentrations by 3 to 5 months.
The authors noted that understanding immune memory of SARS-CoV-2 is important to improving diagnostic tests and vaccines and for predicting future pandemic activity. Noting that immune memory varies among recovered COVID-19 patients, they called for long-term studies to better understand these variations and what they mean in terms of immunity.
"Nevertheless, our data show immune memory in at least three immunological compartments was measurable in ~95% of subjects 5 to 8 months [after infection], indicating that durable immunity against secondary COVID-19 disease is a possibility in most individuals," the authors wrote.
Jan 6 Science study
Smoking tied to worsen COVID-19 symptoms, more hospitalization
Yesterday in Thorax, researchers used data collected from the British ZOE COVID Symptom Study App to show that smoking is tied to a worsening of COVID-19 symptoms and that smokers were more likely to be hospitalized for treatment.
Eleven percent of the 2.4 million participants of the symptom study self-identified as smokers, and 35% said they felt unwell in March and April of 2020. Those who said they were current smokers were 14% more likely to report three main symptoms of COVID-19—fever, persistent cough and shortness of breath—than were non-smokers.
Smokers were also twice as likely to be hospitalized for their infections. The trend for worsening disease in smokers follows other respiratory diseases, the authors said: Smokers are five times as likely to develop influenza and twice as likely to have pneumonia as non-smokers.
Overall, about 15% of the UK's population describe themselves as smokers.
"The present data suggest that smoking cessation should be considered as an element in strategies to address COVID-19, as smoking increases both the likelihood of symptomatic disease defined according to the presence of 'classic' symptoms of fever, cough and breathlessness and the severity of disease, defined based on the number of symptoms," the authors concluded.
In a King's College London news release today, senior author Dr. Mario Falchi said, "Some reports have suggested a protective effect of smoking on COVID-19 risk. However, studies in this area can easily be affected by biases in sampling, participation and response. Our results clearly show that smokers are at increased risk of suffering from a wider range of COVID-19 symptoms than non-smokers."
Jan 5 Thorax study
Jan 6 King's College news release