First Results Announced From Study On Antibodies Against SARS-Cov-2 On Cyprus Population

Preliminary data from an ongoing study in Cyprus show that antibody levels following vaccination with the first and second dose against COVID-19 are at much higher levels than on people who were infected with the disease, as well as that the levels drop a few months after the second vaccine dose, the University of Cyprus Biobank announced on Monday.

These data have not been included in the publication of the study but are in line with relevant observations made by other scientists studying different populations and enhance the view that a decision for a third booster vaccine dose was appropriate, the press release said. Studies by scientists in different countries, it added, have shown that although there is no absolute correlation, it has been observed that antibody levels reflect to a certain degree the adequacy of immunity of the organism.

“Our team stresses that vaccination is the best method of protection against COVID-19 at a personal, family and social level,” the press release notes.

IgG levels

In particular, the University of Cyprus Biobank announced the first results of a study carried out on the production of circulating immunoglobulin class G (IgG) antibodies against SARS-CoV-2 in individuals with past infection in Cyprus. Τhe conclusions of the study say, among other things, that IgG levels increase in the first three months post infection and then decrease, but remain detectable more than six months post infection.

A press release circulated by the University of Cyprus says that the study was done in cooperation with the Department of Health Sciences, School of Sciences, European University Cyprus, the Department of Basic and Clinical Sciences, University of Nicosia Medical School and the Medical School, University of Cyprus.

Individuals of the general population, with or without previous SARS-CoV-2 infection, were invited to visit the Biobank at the Center of Excellence in Biobanking and Biomedical Research of the University of Cyprus. Serum IgG antibodies were measured using the SARS-CoV-2 IgG and the SARS-CoV-2 IgG II Quant assays of Abbott Laboratories.

Antibody responses to SARS-CoV-2 were also evaluated against participants’ demographic and clinical data.  The median levels of receptor binding domain (RBD)-specific IgG in 969 unvaccinated individuals, who were reportedly infected between November 2020 and September 2021, were 432.1 arbitrary units (AI)/mL (interquartile range—IQR: 182.4–1147.3).

Antibody levels

According to the study, higher antibody levels were observed in older participants, males, and those who reportedly developed symptoms or were hospitalised. The RBD-specific IgG levels peaked at three months post symptom onset and subsequently decreased up to month six, with a slower decay thereafter. IgG response to the RBD of SARS-CoV-2 is bi-phasic with considerable titer variability. Levels of IgG are significantly associated with several parameters, including age, gender and severity of symptoms.

The scientists note that although much is known about the basics of SARS-CoV-2 epidemiology in Cyprus, there are still unanswered questions concerning the immune response of the Cypriot population to SARS-CoV-2.

“Understanding the development and durability of humoral immune response among residents in Cyprus is an important scientific and public health task. The aim of this work is to describe the antibody response (N-IgG and receptor binding domain (RBD)-specific IgG) to natural SARS-CoV-2 infection among people living in Cyprus and determine parameters associated with that response”, the study says.

Volunteers

In total, 1,898 volunteers were enrolled in the study (19 November 2020–24 September 2021) and were tested for SARS-CoV-2 IgG antibodies. Of these, 1,112 individuals (58.6%) had reportedly been infected with SARS-CoV-2 in the past, while 786 individuals (41.4%) were not aware of a previous SARS-CoV-2 infection.

The median age of the participants was 46 years old (IQR: 35–57), 1,126 (59.3%) were males, and most of them (n = 1,413, 74.5%) were residents of Nicosia, the largest district in the Republic of Cyprus. Individuals who reported a history of vaccination (40% were reportedly partly vaccinated and 36% fully vaccinated against COVID-19) were excluded from the analyses. The final dataset included 1,132 individuals, of whom 969 (85.6%) had a self-reported history of previous SARS-CoV-2 infection and 163 (14.4%) did not.

In the conclusions of the study the authors say that their work examines for the first time the antibody response to natural SARS-CoV-2 infection in the Cypriot population using both qualitative and quantitative antibody measurement methods.

“We demonstrate that IgG levels increase in the first three months post infection and then decrease but remain detectable more than six months post infection. Circulating IgG levels show substantial variability, partly explained by differences across convalescent individuals in terms of gender, age, development of symptomatic disease, and necessity for hospital care. Overall, our work provides information on the immunological response to SARS-CoV-2 infection that could help inform public health measures and interventions in Cyprus”, they say.

Source: CNA