Kinetics of immune responses to the AZD1222/Covishield vaccine with varying dose intervals in Sri Lankan individuals

Abstract

Background: To understand the kinetics of immune responses with different dosing gaps of the AZD1222 vaccine, we compared antibody and T cell responses in two cohorts with two different dosing gaps. Methods: Antibodies to the SARS-CoV-2 virus were assessed in 297 individuals with a dosing gap of 12 weeks, sampled 12 weeks post second dose (cohort 1) and in 77 individuals with a median dosing gap of 21.4 weeks (cohort 2) sampled 6 weeks post second dose. ACE2-blocking antibodies (ACE2-blocking Abs), antibodies to the receptor-binding domain (RBD) of variants of concern (VOC), and ex vivo T cell responses were assessed in a subcohort. Results: All individuals (100%) had SARS-CoV-2-specific total antibodies and 94.2% of cohort 1 and 97.1% of cohort 2 had ACE2-blocking Abs. There was no difference in antibody titers or positivity rates in different age groups in both cohorts. The ACE2-blocking Abs (p < .0001) and antibodies to the RBD of the VOCs were significantly higher in cohort 2 compared to cohort 1. 41.2% to 65.8% of different age groups gave a positive response by the hemagglutination assay to the RBD of the ancestral virus and VOCs in cohort 1, while 53.6%-90% gave a positive response in cohort 2. 17/57 (29.8%) of cohort 1 and 17/29

Comparison of the immunogenicity of five COVID‐19 vaccines in Sri Lanka

“…The number of individuals who gave a positive response for the total antibody responses (IgG, IgA and IgM) to the RBD of the virus, and ACE2 receptor blocking antibodies for the entire cohort and for different age groups, by vaccine type is given in Table 1 and Figure 1a . As we have previously shown, all those who received the two doses of the AZD1222 vaccine had seroconverted [ 9 ], whereas the overall seroconversion rate for Sinopharm was 95.07% [ 8 ]. All individuals (100%) who had received both doses of the Sputnik vaccines, 94.2% of individuals who received Moderna and 94.5% of those who received Sputnik light had seroconverted based on the presence of RBD binding total antibodies measured by the Wantai assay.…”

“…In contrast, the positivity rates for the WT and VOC in those who received two doses of Sputnik V were between 68% and 80%. Although these positivity rates for Sputnik V were higher than those seen following two doses of AZD1222 (50% to 65%) in 20 to 39 and 40‐to‐59‐year age groups [ 9 ], the positivity rates were lower than those following Moderna.…”

“…In those who received Sputnik light, blood samples were taken 3 months post‐vaccination. The data for individuals who received AZD1222 (12 weeks gap between the two doses) [ 9 ] and the Sinopharm/BBIBP‐CorV [ 8 ] have been previously described. These data on antibody responses to these two vaccines we described in these two studies were then used to compare the immunogenicity of these two vaccines with Moderna and Sputnik light and Sputnik V.…”

“…A direct comparison between four different vaccines showed that 2 to 3 months post immunization showed that the Pfizer‐BioNTech (BNT162b2), elicited the highest levels of ACE2 blocking antibodies, followed by AZD1222, Sputnik V and Sinopharm [ 6 ]. Furthermore, the waning of Nabs and T cell responses with time has been shown to vary widely for different vaccines [ 7 , 8 , 9 ]. Differences in the induction of Nabs and their persistence is likely to have a significant impact on the transmission dynamics of the SARS‐CoV‐2 variants of concern (VoC), especially with the emergence of the omicron variant.…”

“…Some individuals were also vaccinated with Sputnik V and due to the late arrival of the second dose of Sputnik V, many individuals only received the first dose of the Gam‐COVID‐Vac (rAd26‐S/Sputnik light), which is marketed as a single dose vaccine. We had previously published, and data on the kinetics of antibody and T cell responses to the AZD1222 [ 9 ] and the Sinopharm vaccine in the Sri Lankan population, which showed significant differences. In order to get a better idea regarding the differences in immunogenicity of different vaccines, we wished to build on that data, by carrying out a direct comparison for the immunogenicity of different vaccines, at the same time point post‐vaccination.…”