Abstract
BACKGROUND AND OBJECTIVES: Little is known about the efficacy and durability of anti-RBD IgG antibodies induced by certain SARS-CoV-2 vaccines. It has been shown that neutralizing antibodies are associated with the protection against re-infection. This study aims to compare the mean titers, duration, and efficacy of generating protective anti-RBD IgG antibody response among recipients of Pfizer/BioNTech, AstraZeneca, Sputnik V, Johnson & Johnson, Moderna, and Sinopharm COVID-19 vaccines. In addition, we aimed to compare the susceptibility of getting COVID-19 breakthrough infections after various types of vaccines. MATERIALS AND METHODS: Samples from 2065 blood bank donors and healthcare workers at King Hussein Cancer Center (KHCC) were collected between February and September 2021. Anti-Spike/RBD IgG levels were measured using Chemiluminescent microparticle-immunoassay (CMIA) (ARCHITECT IgG II Quant test, Abbott, USA). RESULTS: The mean titer of anti-RBD IgG levels was significantly diverse among different types of vaccines. The highest titer level was seen in participants who took a third booster vaccine shot, followed by Pfizer/BioNTech, AstraZeneca, and Sinopharm vaccine. The mean titer levels of anti-RBD IgG antibodies in the Pfizer vaccinated group was the highest after vaccination but started to drop after 60 days from vaccination unlike AstraZeneca and Sinopharm vaccine-induced antibodies where the mean titers continued to be stable until 120 days but their levels were significantly lower. Most of the breakthrough infections were among the Sinopharm vaccinated group and these breakthroughs happened at random times for the three main types of vaccines. CONCLUSIONS: Our data demonstrate that the mean-titer of anti-RBD IgG levels drop after four months which is the best time to take the additional booster shot from a more potent vaccine type such as mRNA vaccines that might be needed in Jordan and worldwide.