Findings published this week in an online edition of Science could mean that Covid-19 survivors could have protective immunity for months. Analysis of blood samples of 188 Covid-19 patients, suggests that the adaptive immune system response can last for at least eight months after the onset of the initial infection.
Virus-specific antibodies were found to have persisted in the bloodstream months after infection. However, importantly memory B cells were also found to be ready for reactivation to produce Covid-19 antibodies to fight reinfection.
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Moreover, because Covid-19 uses its spike protein to infect cells, researchers looked for B cells specific for Covid-19 and discovered that these cells increased in the blood six months after infection. Additionally, those studied had a multitude of different T cells, such as memory CD4+ ready to trigger an immune response and CB8+ cells ready to destroy infected cells.
Covid-19 antibodies continued long-lasting protection is good news for the vaccines
Researchers said that this new data clarifies some concerning previous data indicating a drop-off of Covid-19 antibodies in the months following infection, which would not allow the body to fight reinfection.
Co-lead of the study Professor Alessandro Sette explained that a decline in antibodies is to be expected: "Of course, the immune response decreases over time to a certain extent, but that is normal. That is what immune responses do. They have a first phase of ramping up, and after that fantastic expansion, eventually, the immune response contracts somewhat and gets to a steady state."
Although on reinfection, researchers cautioned that this finding is heavily reliant on an individual’s immune protective memory and, therefore, varies from person to person, with some people being vulnerable to catching the virus or infecting others.
Research Assistant Professor Daniela Weiskopf said that the findings of this study are good news for vaccine developers, even if those studied were natural responses to Covid-19 infection rather than vaccination: "Our studies showed that natural infection induced a strong response, and this study now shows that the responses lasts. The vaccine studies are at the initial stages, and so far, have been associated with strong protection. We are hopeful that a similar pattern of responses lasting over time will also emerge for the vaccine-induced responses."