As the COVID-19 global pandemic enters its second year, scientists now have data on some of the long-term effects of the infection, which is caused by the SARS-CoV-2 virus. A new report details the efficacy of the immune response months after beating the active infection. The paper also reports possible chronic complications from COVID-19.

The immune system utilizes both rapid-acting and long-term defenses against infection. Plasma B cells produce antibodies to fight active infections, while memory B cells circulate throughout the body for months or years after an infection has ended, ready to attack if re-infection occurs. However, because viruses evolve and change their genome quickly, antibodies may be less effective over time.

The investigators assessed 87 participants for approximately one to six months after infection. They collected blood from participants to assess memory B cell quantity, antibody quantity, and the ability of antibodies to neutralize the virus after infection. Participants reported symptoms using common surveys.

The number of antibodies specific for the SARS-CoV-2 spike antigen decreased significantly from 1.3 to 6.2 months after infection, and the ability of these antibodies to neutralize the virus decreased fivefold. However, memory B cell concentrations were slightly increased, leading to the authors to conclude that immunity was intact 6.2 months after infection. Additionally, the authors reported that participants who experienced the most severe cases of COVID-19 were more likely to report chronic symptoms of shortness of breath, fatigue, unexplained fever, neurological abnormalities, and others.

These findings suggest that immunity to the SARS-CoV-2 virus lasts at least six months after infection. It is important to note that this article is in pre-print and has not yet been peer-reviewed.

• Link to full study.