Protective humoral and cellular immune responses to SARS-CoV-2 persist up to 1 year after recovery

Abstract

SARS-CoV-2 vaccination has been launched worldwide to build effective population-level immunity to curb the spread of this virus. The effectiveness and duration of protective immunity is a critical factor for public health. Here, we report the kinetics of the SARS-CoV-2 specific immune response in 204 individuals up to 1-year after recovery from COVID-19. RBD-IgG and full-length spike-IgG concentrations and serum neutralizing capacity decreases during the first 6-months, but is maintained stably up to 1-year after hospital discharge. Even individuals who had generated high IgG levels during early convalescent stages had IgG levels that had decreased to a similar level one year later. Notably, the RBD-IgG level positively correlates with serum neutralizing capacity, suggesting the representative role of RBD-IgG in predicting serum protection. Moreover, viral-specific cellular immune protection, including spike and nucleoprotein specific, persisted between 6 months and 12 months. Altogether, our study supports the persistence of viral-specific protective immunity over 1 year.

Persistence of SARS-CoV-2-Specific Antibodies for 13 Months after Infection

“…All participants who were identified as seropositive 2 months after the outbreak (n = 34) maintained the seropositivity for 6 months after the confirmed SARS-CoV-2 infection. This result is in agreement with many other studies demonstrating the persistence of SARS-CoV-2-specific antibodies for at least 6 months after infection [9,12,13,15,16,21,27]. More than one third of seropositive individuals had virus-specific IgM along with IgG, which indicates that IgM may persist for 6 months, thus providing additional confirmation that IgM is not a suitable marker for identifying early infection due to expected high falsepositivity for previously infected individuals [9,11,18].…”

“…Excluding the known reinfection case, the seropositivity rate after 13 months was high with antibodies present in 38 out of 46 participants suggesting that detectable levels of virus-specific antibodies persist in a majority of the cases. The comparison of ELISA results 6 months and 13 months after the outbreak revealed sustained IgG levels in 14 participants and a decline of IgG levels in 17 participants, which is in agreement with other studies indicating a gradual decline of circulating antibodies after infection [12,16,17,24,33,34]. Interestingly, the levels of virus-specific IgG increased in 7 participants without any documented reinfection using periodically performed RT-PCR tests or self-reported symptoms.…”

“…Data on the persistence of the SARS-CoV-2-specific immune response are of great importance for managing the pandemic and planning further measures for increasing the population's resistance to the virus. To date, both sero-epidemiological and targeted cohort studies from different countries have reported detectable levels of virus-specific antibodies and duration of the protective immune response from 3 to 13 months after infection [6,7,10,12,13,17,19,21,24,25]. Previous cohort studies on the formation and persistence of SARS-CoV-2-specific humoral immune response mainly included healthcare workers as a target group having the highest risk of being exposed to SARS-CoV-2 [13,14,16,19,20,24,26,27].…”

“…A significant increase in virus-specific antibody levels is observed at days 16-35 after the onset of symptoms [4,[7][8][9][10]. Some studies have reported that antibody levels peak within the first few months, then wane and remain stable for several months, indicating that the immunity may last longer [4,8,[10][11][12][13][14][15][16]. Other studies suggest that the levels of SARS-CoV-2-specific IgG are durable and decline after 6-8 months while the number of memory B cells increases within 8 months after infection [17,18].…”

What Happens to the Immune System after Vaccination or Recovery from COVID-19?

“…On the other hand, the durability of immunity to SARS-CoV-2 remains unclear since there is a decline in circulating antibody titres a few months after recovery or vaccination [148][149][150]. In turn, some authors have found sustained T-cell immunity despite a decline in the antibody response months after infection [151,152], suggesting that other immune components contribute to protective immunity.…”