Durability of SARS-CoV-2 Specific IgG Antibody Responses Following Two Doses of Match and Mixed COVID-19 Vaccines Regimens in Saudi Population

Abstract

Background SARS-CoV-2 pandemic continues to threaten the human population with millions of infections and deaths worldwide. Vaccination campaigns undertaken by several countries have resulted in a notable decrease in hospitalization and deaths. However, with the emergence of new virus variants, it is critical to determine the longevity and the protection efficiency provided by the current authorized vaccines. Aim The aims of this study are to provide data about the magnitude of immune responses in individuals fully vaccinated against COVID-19 in Riyadh province of Saudi Arabia. Also, to evaluate the continuity of specific IgG levels and compare the titers in individuals who have been received two doses of the matched and mixed vaccines, including Pfizer and AstraZeneca against SARS-CoV-2 during the period of three to six months. Moreover, we analyze the current state of immune response in terms of antibody responses in thepopulation postvaccination using homogenous or hetrogenous vaccine regimen. Methods A total of 141 healthy volunteers were recruited to our study; blood (n=63) and the saliva samples (n=78) and were collected from fully vaccinated individuals in Riyadh city. We employed a specific ELISA assay in plasma and saliva of fully vaccinated individuals. Results IgG levels varied with age groups with the highest concentration in the age group 19–29 years, but the age group (≥50) had the lowest IgG concentration. The IgG levels in both serum and saliva were higher after three months and start to wane after six months. Individuals who received mixed types of vaccines had significantly better response than Pfizer vaccine alone. Conclusion The current study investigates the status of humoral responses in different age groups, in terms of antibody measurements. These data will help to evaluate the need for further COVID-19 vaccine doses and to what extent a two-dose regimen will protect vaccinated individuals.

Predictors of SARS-CoV-2 anti-Spike IgG antibody levels following two COVID-19 vaccine doses among children and adults in the Canadian CHILD Cohort

“…SARS-CoV-2 anti-spike IgG antibody levels were lower in adults than children in our study, consistent with evidence in other studies that adults have reduced humoral responses to COVID-19 vaccine and other vaccine types compared to children 17–23 . We did not detect any sex differences, contrasting with other studies that found higher SARS-CoV-2 anti-spike IgG antibody levels in females compared to males 20,21,24,25 . However, similar to our findings, Brlić P. et al reported no significant gender-related differences in post-vaccination antibody levels among a cohort of 1072 healthcare workers in Croatia 26 .…”

“…While our study did not evaluate the chronological order of natural infection and vaccine-induced immunity, our data agrees with findings from cohorts of healthcare workers in Spain 30 , USA 36 and Kuwait 37 where individuals with prior COVID-19 had higher vaccine-induced antibody response. SARS-CoV-2 anti-spike IgG antibody levels were lower in adults than children in our study, consistent with evidence in other studies that adults have reduced humoral responses to COVID-19 vaccine and other vaccine types compared to children [17][18][19][20][21][22][23] . We did not detect any sex differences, contrasting with other studies that found higher SARS-CoV-2 anti-spike IgG antibody levels in females compared to males 20,21,24,25 .…”

“…This is not surprising as mRNA vaccines induce more rapid humoral responses through short-lived plasma blasts compared to viral-vector vaccines 30 , in both plasma and saliva. 21 SARS-CoV-2 anti-spike IgG antibody levels appear to wane three months after receipt of a second vaccine dose in our cohort. Similarly, a prospective general cohort study in Holland involving 2412 double-vaccinated participants showed a decline in antibody levels beginning at around four to six months post-vaccination 30 .…”

The Frequency of SARS-CoV-2 Anti-spike RBD IgG Antibodies in the Fully Vaccinated and Recovered COVID-19 Infected Individuals.

“…Head-to-head comparison of the developed RBD protein against TECAN IgG ELISA kit proved that there were non-significant differences between results as the negative control group tested nonreactive and all post-vaccinated samples were seropositive. These findings are consistent with previous studies [12] [13]. Whilst the sensitivity of the developed RBD protein was 88.4% (95% CI: 84% -92%) with 100% specificity (95% CI: 88%-100%) in the pre-vaccinated group.…”

“…Prior studies addressed the longevity of the IgG immunoglobulin response after the active immunization. Several studies reported that the persistence of IgG antibodies was highest at the first 3 months and started to decline during 6-8 months after a full vaccination with mRNA-based and viral vectorbased vaccines [12] [23] [24] [25] [26] [27]. In the current study, the median time after the full vaccination was 85 days, and all post-vaccinated samples were seropositive.…”