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A transient neutralizing Ab (nAb) response is a feature shared by both COVID19 infection and the coronaviruses that cause common colds (https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v1)
Antibody (Ab) responses to SARS-CoV-2 can be detected in most infected individuals 10-15 days following the onset of COVID-19 symptoms. Seroconversion occurred in >95% of cases and neutralizing antibody (nAb) responses.
All subjects, regardless the disease severity and the magnitude of the Ab response showed a decline of the nAb titres within 60 days post infection.
Ab responses targeting endemic coronaviruses that cause common colds can last for as little as 12 weeks, whereas Abs to SARS-CoV and MERS can be detected in some individuals 12-34 months after infection.
Many current vaccine design efforts focus on eliciting a robust nAb response to provide protection from infection. Vaccine candidates tested thus far in animal challenge studies have elicited modest nAb responses. Vaccine challenge studies in macaques can give limited insight into nAb titres required for protection from re-infection.
However, the role T-cell responses generated through either infection or vaccination play in controlling disease cannot be discounted in these studies and defining further the correlates and longevity of vaccine protection is needed.
Declining nAb titres in the majority of individuals. For those with a low nAb response, titres can return to base line over a relatively short period. Further studies using sequential samples from these individuals is required to fully determine the longevity of the nAb response and studies determining the nAb threshold for protection from re-infection are needed.
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