HealthDay News — Antibody levels appear to remain positive for up to nine months after severe acute respiratory syndrome coronavirus 2 infection, according to a study published online July 19 in Nature Communications.
Ilaria Dorigatti, Ph.D., from Imperial College London, and colleagues conducted two mass swab testing campaigns in Vo’, Italy, in February and March 2020, and then tested 86 percent of the Vo’ population with three immuno-assays detecting antibodies against the spike and nucleocapsid antigens, a neutralization assay, and polymerase chain reaction (PCR) in May 2020. In November, individuals testing positive to PCR in February/March or to a serological assay in May were tested again.
The researchers found that in May 2020, the seroprevalence was 3.5 percent. In November, 98.8 percent of the sera that tested positive in May still reacted against one or more antigen; compared with May, 18.6 percent showed an increase of antibody or neutralization reactivity in November. In an analysis of the serostatus of members of 1,118 households, the susceptible-infectious transmission probability was 26.0 percent.
“We found no evidence that antibody levels between symptomatic and asymptomatic infections differ significantly, suggesting that the strength of the immune response does not depend on the symptoms and the severity of the infection,” Dorigatti said in a statement.