SARS-CoV-2 Infection in Fully Vaccinated Individuals of Old Age Strongly Boosts the Humoral Immune Response

Abstract

Prophylactic vaccination against SARS-CoV-2 is one of the most important measures to contain the COVID-19 pandemic. Recently, break-through infections following vaccination against this virus have been reported. Here, we describe the humoral immune response of break-through infections in fully vaccinated individuals of old age from an outbreak in a nursing home. In cooperation with the local health authority, blood samples from fully vaccinated and infected as well as fully vaccinated and uninfected residents of the nursing home were collected 4 weeks after the onset of the outbreak. The humoral immune response was determined in a neutralisation assay with replication-competent virus isolates and by a quantitative ELISA. In this outbreak a total of 23 residents and four health care workers were tested positive for SARS-CoV-2. Four residents were unvaccinated, including one with a severe course of disease who later severe disease course who later succumbed to infection. Despite their old age, all vaccinated residents showed no or only mild disease. Comparison of the humoral immune response revealed significantly higher antibody levels in fully vaccinated infected individuals compared to fully vaccinated uninfected individuals (p < 0.001). Notably, although only a minority of the vaccinated uninfected group showed neutralisation capacity against SARS-CoV-2, all vaccinated and infected individuals showed high-titre neutralisation of SARS-CoV-2 including the alpha and beta variant. Large SARS-CoV-2 outbreaks can occur in fully vaccinated populations, but seem to associate with mild disease. SARS-CoV-2 infection in fully vaccinated individuals is a strong booster of the humoral immune response providing enhanced neutralisation capacity against immune evasion variants.

Adjusted booster schedules disperse age-dependent differences in antibody titers benefitting risk populations

“…In the group of convalescent individuals, the humoral immune response was significantly increased compared to the vaccinated cohort, which is in line with previous results [16].…”

“…In the group of convalescent individuals, the humoral immune response was significantly increased compared to the vaccinated cohort, which is in line with previous results [16]. While a high number of convalescents was infected during an Omikron BA.1 outbreak shortly before the second follow-up blood collection, both Omikron neutralization titers were lower than the neutralization titers against the B.1 WT, although neutralization titers against the WT were also significantly increased, suggesting a simultaneous induction of cross-reactive neutralizing antibodies against both variants [17].…”

Comparison of the Clinical and Laboratory Findings and Outcomes of Hospitalized COVID-19 Patients Who Were Either Fully Vaccinated with Coronavac or Not: An Analytical, Cross Sectional Study

“…Although the mean S/CO of anti-S IgG on the 7th day of complaints among Coronavac-vaccinated inpatients was higher than that among unvaccinated inpatients in our study, the numbers were found to be very close to one another, at 6.11 vs. 5.14, respectively. However, it was shown that SARS-CoV-2 breakthrough infections are a strong booster of the humoral immune response among fully vaccinated patients, the anti-spike IgG antibody levels were increased significantly as low as 2 to 4 days after the onset of symptoms of breakthrough infections, and the levels were more than 10-fold higher in fully vaccinated infected individuals than in unvaccinated uninfected individuals [ 12 , 27 , 28 ]. These findings also support the lower response rate to the Coronavac vaccine in our cohort.…”

Adjusted COVID-19 booster schedules balance age-dependent differences in antibody titers benefitting risk populations

“…A serial dilution endpoint neutralization test was performed with an infectious SARS-CoV-2 B.1 WT (EPI_ISL_425126), Omikron BA.1 (EPI_ISL_12813299.1) and BA.5 (EPI_ISL_14167576) isolate as previously described ( Müller et al, 2021 ).…”