A Prospective Study on Rapidly Declining SARS‐CoV‐2 IgG Antibodies Within One to Three Months of Testing IgG Positive: Can It Lead to Potential Reinfections?

Abstract

Background COVID-19 immunoglobulin G (IgG) antibodies have been considered to provide protective immunity and its immunoassays have been widely used for serosurveillance. In our serosurveillance on an industrial workforce of randomly selected 3296 subjects, COVID-19 IgG antibody positivity was reported in 7.37% (243) subjects. However, when 30 days later, eight of the 243 COVID-19 IgG antibody-positive individuals complained of symptoms suggestive of COVID-19 infection and were confirmed as COVID-19 infection by reverse transcription-polymerase chain reaction (RT-PCR), their COVID-19 IgG antibodies were retested. Seven of the eight previously IgG positive individuals had lost their protective antibodies. Methods Subsequently, a prospective clinical trial was planned by repeating the test for IgG antibodies on the remaining earlier positive 235 individuals at 45-65 days after their initial test. Only 201 of the 235 individuals consented and participated in the non-randomized single-arm observational trial. Results Only 28.36% (57/201) retained their IgG antibodies and 70.15% (141/201) had lost their IgG antibodies. Three cases reported equivocal results on retesting. Conclusions Our findings show that the protective COVID-19 IgG antibodies rapidly decline over one to three months. Further studies are needed with a quantitative assay over a period with neutralizing antibodies to establish if its decay can potentially lead to reinfections. Rapidly decaying protective IgG antibodies would impact herd immunity and vaccine durability. It is critical for the potential vaccines to generate both protective T-and Bcell immune responses in a sustained manner.

Serosurveillance of Health Care Workers in a COVID Hospital: Immune Response, and Its Longevity

“…The other important question is whether HCWs with previous infection or measurable antibodies are immune to reinfections and hence, can be deployed in high-risk areas [11]. While some initial studies have shown that 40% of asymptomatic subjects and 12.9% of symptomatic subjects became seronegative for IgG antibodies in the "early convalescent phase", there are other isolated reports of rapid decay of IgG antibodies in persons with mild infection [21][22][23][24]. The longevity of the immune response and the level of neutralizing antibodies needed for protection remain unclear, as cases of relapse/reinfection with SARS-CoV-2 have been reported [21].…”

Waning antibody responses in COVID-19: what can we learn from the analysis of other coronaviruses?

“…Overall, IgM, IgG and nAb titres peak ~ 2–3 weeks post-symptom onset and decline to undetectable levels by 6 weeks for IgM, whereas IgG and nAb reach a plateau before declining within 2–3 months (Fig. 1 b) [ 6 , 55 – 57 ]. Mathematical modelling estimates that within 1 year IgG antibodies to nucleocapsid, spike protein and RBD wane to 7%, 36% and 31% of their titres at 2 weeks post-symptom onset, respectively [ 58 ].…”

Serosurveillance of Anti SARS-Cov-2 Antibodies among Essential Workers in Navi Mumbai - A Single Centre Study

“…(17 -20) The longevity of the immune response and the level of neutralizing antibodies needed for protection remain unclear, as cases of relapse/reinfection with SARS-CoV-2 have been reported. (17) The variation in the immune response could be attributed to the symptomatology, being less in milder infections, the constitution of individuals, or nutritional status. (21) Thus, further studies are needed to better understand the possible relationship between these factors and variation in the development of antibodies.…”